1



### Study conducted for the German Federal Environment Office

Sponsorship Reference 360 09 006



## Emission of Refrigerant R-134a from Mobile Air-Conditioning Systems

Annual Rate of Emission from Passenger-Car Air-Conditioning Systems up to Seven Years Old

by

Dr. Winfried Schwarz



### Öko-Recherche Büro für Umweltforschung und -beratung GmbH Environmental Research and Consultancy Office

Frankfurt am Main

September 2001I



### Contents

Rate of Emission from Car Air-Condi tioning Systems up to Seven Years Old. Introduction and Summary. III

Purpose of Empirically Based Study III

High Refrigerant Loss attributable to System Design III

Summary of Chapters A to G IV

I. Refrigerant Record Sheets and Supplementary Information from the selected Garages 1

1. Refrigerant Records voluntarily completed by garages 1 2. Time-span and quality of garage Record Sheets on R-134a 1 3. Concentration of vehicles: Rhine-Maine Region 2 4. Three German brands of passenger car 2 5. Recovery/recharging stations employed 2 6. First stage of quantity correct ion - the 1,004 documented cases 2 7. Second stage of quantity correction - the 841 analysable cases 4 8. Other information from the gar ages and the car manufacturers 5 9. Workshop visits for opening of air-conditioning system distributed over individual months 5 

### B. Reliability of Records and Accuracy of Recovery/Recharging Stations 7

I. Recovery and Charging by Recovery/Recharging Station (see drawing) 7

1. Recovery (2 to 5 minutes) 7 2. Evacuation (20 to 30 minutes) 9 3. Recharging (1 to 3 minutes) 9 4. Emptying the recharging hose 9 

### II. Errors in determining Quantity; their Significance and Correction 10

1. Rounding off when measuring by sight, also where weighing electronically 10

2. The residue in the hose as source of error in determining the charge quantity 11 3. Temperature differences between recovery/recha rging station and air-conditioning system when recovering 12 4. Recovery of after-evaporation forgotten 13

5. Omitted entries 13 

### III. Refrigerant Loss caused by the Servicing Operation itself 14

1. Loss when charging 14 2. Refrigerant loss when locating leaks with contrast medium 14 

### C. Reasons for Opening an Air-Conditi oning System and Causes of Detected Refrigerant Loss 16

I. Elimination of Leaks, the Main Reason for Opening on Total Loss of Refrigerant 17

1. Empty air-conditioning system after accident involving body damage 18 2. Total loss due to stone impact or irregular component defect 18 3. Total loss followed simply by recharging without repair work 19 

### II. Opening a System where Refrigerant Loss is less than 40% 20

1. Component defects not themselves responsible for release of refrigerant 21 2. Air-conditioning system as obstacle to engine or radiator repairs 22 3. Establishment of accident damage and preparation for bodywork repairs 22

4. Leak tests at customer's or workshop's initiative 23 

### III. Consequences for Method of Estimating the Rate of Emission 23



### D. The Annual Rate of Normal Emission 25

I. Regular Loss of Refrigerant from Intact Air-Conditioning Systems 25II



### II. All 282 Emission Rates of < 40% as a Function of Vehicle Age 25

III. Statistical Correction of Normal Emission Rates 27

1. Recognisable as 'irregular' from the Record Sheets: seven cases 27 2. Eliminating anomalies above and below the line: 59 cases 28


### IV. The corrected 6.3% Annual Rate of Normal Emission 30

V. Differences in Normal Emission between the Three Car Brands 31

VI. Car Manufacturer Specifications concerning Normal Leakage 33


### E. The Annual Rate of 'Irregular' Emission 35

I. Inspections as Reference Quantity for Cases of Irregular Emission 35

II. Confinement of Inspections to Vehicles with Air-Conditioning System 36

1. Model of Age Patterns in Annual Inspections 37 2. Air-conditioning quotas in inspection periods 1999, 2000 and 2001 38 3. 'Workshop Rate' of air-conditioned vehicles 39 

### III. The Annual Rate of 'Irregular' Emission 39



### F. The Annual Total Rate of Emission fo r Air-Conditioning Syst ems at most Seven

Years old 41

I. The Calculated 8.2% Rate of Emission 41

II. Margins of Error in determined Quantities 42

1. Errors in recording recovery and recharging operations 42

2. Differences between the three brands of car 42 

### III. The Annual Rates of Emission with Margins of Error 43

IV. Emission on Disposal raises the Annual Rate by 10% 43



### G. The Question of Reduc ing Emission by Regular System Inspection 45

I. Maintaining an Air-Conditioning System increases Operational Reliability 45

II. Regular Maintenance generally does not reduce Emission 45

III. Partial Prevention of Irregular Emission - Minimal 46

1. Two examples showing how emission may be reduced by maintenance 46 2. Internal corrosion by acid refrigerant is unlikely 46 3. Detection of slowly growing small leaks 47 4. Emissions prevented or caused by main tenance are approximately equal in magnitude. 48 

### Acknowledgements, Reference Material 49

Note on unnamed sources 49

References 49



### A special debt of gratitude is due to Mr Matti Vainio for his initiative to have this study translated from German into English by the European Commission.III



## Rate of Emission from Car Air-Conditioning Systems up to Seven Years Old. Introduction and Summary.

The Kyoto Protocol on Climate Protection extends not only to the greenhouse-gases CO 2 , methane and nitrous oxide, but also to the fluor inated gases (f-gases) HFC, PFC and SF 6 . By far the most important of the fluorinated greenhouse gases is HFC, used ma inly as a substitute for CFCs, while the most significant of the HFCs themselves is HFC 134a, accounting for about three-quarters of world production. Since HFC 134a is mainly used as a refrigerant, it is also called R-134a, 'R' standing for 'refrigerant'.



### Purpose of Empirically Based Study

The greater part of R-134a use in Germany is associ ated with mobile air-conditioning systems. Rather than going by laboratory measurements and the estimati ons of experts, the pr esent study has employed empirical and statistical methods in its attempt to determine the annual rate of R-134a emission from mobile air-conditioning systems. The study should also help in assessing the extent to which preventive maintenance and inspection might contribute to a reduction in emissions.

Our analysis concentrates mainly on passenger-car air-conditioning systems because they account for about 95% of refrigerant emission and consumption in the "mobile air-condi tioning systems" sector ('Öko-Recherche - Ecological Survey - 1999, 17). The survey is bas ed on the records kept by garages on the quantities of refrigerant recovered and rechar ged when opening the refrigerant circuit of an airconditioning system.



### High Refrigerant Loss attributable to System Design

Unlike a stationary air-conditioning system, the refrig erant circuit of a car's air-conditioning system is unstable in state because its compressor is driven by the crankshaft. The compressor is necessarily open in design, and, being attached to the engine bloc k, the need arises to avoid vibration as cooling capacity is transferred to the remaining parts of t he refrigerant circuit connected to the chassis. As a result, only a limited proportion of metallic piping may be used in place of flexible hosing. Hose s, O-rings at component joints, and the rotary shaft seal of t he compressor are weak points in the sealing system (Air-Conditioning Systems Conference - 2001), consti tuting the principal points of normal refrigerant leakage from systems which have not suffered "irregular" damage.

It is generally recognised that the emission of R-134a from car air-conditioning systems is not as high as that of CFC R-12 (still being newly installed up to as late as 1994 in some cases), where losses had amounted to nearly three charges per life cycle. Greate r care is now taken in the handling of refrigerant, and although the HFC-134a molecule is smaller than t he CFC-12's, the additional lining of hose interiors with polyamide film prevents any greater permeation.

At present, however, we have nothing more to go by than a series of estimates of the annual loss of refrigerant from car air-conditioning systems, with fi gures ranging from less than 5% to over 20% based on expert assessment or, rather more rarely, on l aboratory measurement (see Clodic 2000; AFCE 1998; Baker 1999; Preisegger 1999, Öko-Recherche 1999 ; UNEP 1998; Fischer 1997, Pettersen/Hafner 1996, among others). To date, no estimate has yet been put forward on the basis of empirical measurements made on actual road-going vehicles.IV



### Summary of Chapters A to G

Chapter A presents the study database, comprising approximately a thousand recorded recovery and recharging operations carried out by nine authoris ed dealers of three German car manufacturers during the period 1999 to May 2001.

Chapter B discusses recovery/recycling/recharging stat ions, duly examining the accuracy with which volumes recovered and charged are measured, redu cing margins of error, and introducing corrective

factors.

Chapter C analyses the reasons for the detected loss of refrigerant on opening an air-conditioning system. It emerges that the causes of 'total' loss (occurring in approximately 40% of cases and mainly attributable to outside influence) are different fr om the reasons for the equally high number of cases producing losses of less than 40%. A deficit of 40% refrigerant in relation to the normal charge is regarded here as the limit below which an air-conditi oning system is still marginally intact (still no gaseous refrigerant or "flash gas", and still entirely li quid upstream of the expans ion valve) and generally provides the same cooling action as a fully charged system. Provided they do not already occur during the initial phase of a system's use, refrigerant loss es of less than 40% are generally the result of normal leakage rather than an 'irregular' event (accident, st one impact, etc.) which almost always produces greater loss. The study therefore sets out to exam ine two fundamentally different kinds of emission - normal and irregular. Refrigerant loss under 40% is the result of gradual, normal leakage, especially through seals, while the causes of any higher losses than that are 'irregular'. While it is true to say that continuous normal leakage of refrigerant can someti mes reach levels of over 40%, vehicles aged less than six or seven years (representing the majority of our chosen population) should not generally have arrived at that stage so early in their life. For t he present, detected refrigerant loss less than 40% is deemed to be normal leakage.

Chapter D examines air-conditioning systems opened for va rious reasons other t han lack of refrigerant and found to have lost less than 40%, interpreting th em as (unintentional) "random sample" of normal emission, and relates the losses to the age of the vehicl e in months since first registration. Initially, there is no relationship to be seen between the level of re frigerant loss and the age of the vehicle, due in the main to numerous unexpectedly high instances of refr igerant loss during the first eighteen months of operation. Since such instances can be assumed to have 'irregular' rather than normal causes, they were eliminated from the remaining study of norma l emission. Having "removed" these instances of emission from the series of refrigerant losses less than 40%, the remaining 216 air-conditioning systems in the survey indicated a mean annual coolant loss of 6.3% (52 grams) as annual rate of normal emission over the first seven years in use. This ra te varies by about ten percentage points up or down according to make of car, ranging from 5.8 to 7.0%. The mean 52-gram normal leakage figure comes within the scope of the car manufacturers' permitt ed tolerance of 34 to 83 gram per air-conditioning system.

Chapter E: The study determined 'normal' emission indirect ly from garage records, relating the emission behaviour of the few air-conditioning systems opened in the garage to the entirety of passenger-car airconditioning systems in use for less than seven ye ars. However, 'irregular ' emission was determined directly from those records, relating the sum of irregular refrigerant loss in kilograms which a garage detected in one year to the number of air-conditi oned cars inspected by the same garage in the same year. Passing through several intermediate stages, t he examination disclosed an annual loss of about 1.9% of the refrigerant carried in vehicles regula rly serviced by the nine aut horised dealers within the period 1999 to May 2001. The percentage varies from 1.5 to 2.2 % according to make of car.

Chapter F adds the two rates of emission to arrive at an annual rate of 8.2% total emission, which varies from 7.7 to 9.2% according to make of car. To allo w for this fluctuation between car brands and to cater for the inherent inaccuracy of recovery/rechargi ng stations, the margin of error is extended by 25%V

above an d be low the 8.2% figure to prod uce a n ann ua l total rate of emission va rying between 6.2 and

10.3%. This d e fines the ma gnitude rathe r than the ex a c t level of the rate of emission. It should be

remem b e r ed that these fig u re s rel a te on ly to air-c o ndi tioning sy ste m s less than seven yea r s old, and a s yet make no allowan c e for emissi on at time of dispo s al. Regul ar to tal emissi on o f R-134 a from car ai rcon d itioning systems in the year 2000 h a s bee n estim a ted as b e tween 68 5 and 1,140 tonn es. The

variation de p end s on whet her an e m issi on rate of 6.2 % (the minim u m) or 10.3% (the maximu m) is

assume d for the 11,50 0 ton nes of refrige r ant ci rculat ing in pass e nger c a rs in Germany. In turn, this 11,500 ton n e s is an a s sum ed figure b a sed on 13 milli on air-conditi oned cars (30 % of the total car popul ation be ing thus e qui pped ) having an avera ge R-134 a ch arge of 850 gram s.

Annual Rate of Em ission increa sed to 1 0 % on accou n t of Loss at Tim e of Disp osal

To gua rd ag a i nst an y m i sunderstan ding, it should be sa id that an a nnual rate of em ission o v e r

the first

se ven yea r s i

n servi c e will gene rall y be l o we r than an annu al rate of em ission cal c ulate d over the entire life of a syste m . This is not sim p ly due to the accele r a tion in norm a l system leakag e (not qu a n tified in this pap er) which som e experts e x p e ct t o observe a s a vehi cle a g e s , it is m a inly attributable to em ission

at tim e of scrappin g an old car. Eve n wit h the im pr ove m ents expe ct ed in the re co very of ref r ige r ant by

Germ an old

- c a r re c ycl er s o v er t he com i n g yea r s, r e c o ve ry related t o a give n orig inally G e rm a n yea r of regi stratio n will still be lim ited on a c coun t of the 50% quot a of used cars e x po rte d in that year to non-E U

cou n trie s (Arge Altauto 20 00 - Arge ol d cars, 200 0)

. Dispo s al lo ss per ann um is estim a ted here at about

25% until further info rm ation becom es a v aila ble. This 25% distri but ed over a life of twelve to thirteen

yea r s in crea ses the an nual total rate of em ission b y a furthe r 2%, so in the m edium term the rate

fluctuate s aro und ab out 10 %.



### A n n u al R a te o f N o r m al , I r r e g u l a r , D i spo s al an d O v er al l

E m i s s i on s fr om P a ss en g e r C a r A C U n i t s u p to S e v e n Y e a r s old ( 2 5 % m a r g in o f er r o r - i n c l u d in g d i sp o s a l em is s i o n s)

6. 3

1. 9 2. 0 10 .2

0 2 4 6 8 10 12

N o r m al ER I r r e g u l

. ER D i s p o s al ER Ov er al l ERpercentage

Cha p ter G fin a lly examines the likeliho o d of redu cing e m issi on of ref r ige r ant into the enviro n me nt by regul arly mai n taining the a i r-con d itionin g system. In prin ciple, p r e v entive inspe c tion do es in crea se the reliability of a system' s op eration and can also contrib u t e to a saving in energy, bu t it does not redu ce the emission of refrige r ant asso ciat ed wi th either disp osal, 'irreg ula r ' lea k ag e, or norm a l lea k a ge. Acco rdi ngly, it is not deem ed app rop r iat e to introdu ce compul so ry maintena nce alone with a view to

redu cin g the emission of R-134 a.1



## A. Database - Nine Motor-Vehicle Garages

The actual level of refrigerant in an R-134a ai r-conditioning system can only be ascertained by opening the refrigerant circuit in a suction-based recovery operation. While the checking of pressures in combination with temperature measurements may indicate whether or not the system still contains sufficient refrigerant for it to operate, this process ca nnot in fact determine the actual level of refrigerant. Unlike R-12 systems, the collector employed does not have an inspection glass for fast diagnosis. Accordingly, to establish the level of refrigerant and with that the difference in charge, the refrigerant must be recovered entirely from the system by means of a recovery/recharging station.



### I. Refrigerant Record Sheets and Supplem entary Information from the selected Garages

1. Refrigerant Records voluntarily completed by garages

Following on their records of consumption of CFC-refr igerant R-12, some garages in Germany continue to keep "Record Sheets on Quantities of CFC-contai ning Refrigerant consumed in the Maintenance of Air-Conditioning Systems" for the R-134a refriger ant introduced between 1991 and 1993. From the author's experience, this is done by about every one in ten manufacturer-tied ('authorised') workshops or dealership outlets. Half of these garages systematically enter the re covery and charge quantities read off the recovery/recharging station for every singl e air-conditioning system duly opened, and file the list both as record of their own work on the vehicle (f or product-liability purpose s) and as statistical instrument for internal management of resources.

The law does not require any such detailed recording of refrigerant consumption. The German Federal Law on Environmental Statistics ( Umweltstatistikgesetz ) simply rules that, on request, garages should report their total consumption of refrigerant (R-13 4a) in the previous year to their designated Federal State Statistics Office. However, garages were in fact recommended to report vehicle-specific consumption of refrigerant in the standard "Fundam entals of Technical Expertise in Vehicle AirConditioning Systems" leaflet issued by the VDA, ZDIK and ZDK ( German automobile industry

associations ) in the winter of 1996.



### 2. Time-span and quality of garage Record Sheets on R-134a

Between April and July 2001, usable "Record Sheets on Consumption of Refrigerant" were collected from nine manufacturer-tied garages (authorised dealer garages/outlets) associated with three different German car brands, and were duly entered in our computer. The records were deemed 'usable' where they documented at least one full year (calendar-y ear 2000, or the period May 2000 to May 2001) and generally contained the following data:

1. Date of workshop visit, 2. Registration number of vehicle (or a Job Number), 3. Quantity of refrigerant recovered, 4. Quantity of refrigerant charged, 5. Charge difference, 6. Notes (brief) on reason for operation, and 7. Type of recovery/recha rging station employed.

The line indicating reason for recovery and recharging was left uncompleted or was insufficiently informative ("leaking") in half of the cases examin ed, but was adequately specific in the other half ("accident, condenser replaced").2

Five of the nine garages had records on year 1999 as well, three of these also having details on the period May 1998 to end of 1998, and one had even kept information on the whole period March 1997 to May 2001. We also examined any full 'year 1999s'. In complete 'year 1999s' and the parts of years 1998 and 1997 were entered in the computer for control purposes.

Refrigerant R-134 records going back any further than 1997 were inaccessible to the author (except for one very patchily documented 'year 1996').

Where an air-conditioning system undergoes recovery and recharging, garages generally write the type of refrigerant on the customer's invoice and (duri ng the warranty period) on the invoice sent to the manufacturer. However, the record on the invoice notes a full system charge rather than the quantity recovered, which is reasonable enough in view of t he refrigerant-cleansing carried out in the course of opening an air-conditioning system. It is for this re ason that customer invoices have not been used as database for the present study.



### 3. Concentration of vehicles: Rhine-Maine Region

Seven of the reporting garages were in the Rhine- Maine Region, and two were in the Nuremberg area.

This means that about 80% of the documented vehicles with duly maintained air-conditioning systems were reported in the Rhine-Main Region (conc entrated mainly on Frankfurt am Main), 15% in Nuremberg and its environs, and about 5% had regist ration plates from outside those two regions.



### 4. Three German brands of passenger car

In the year 2000, the three German car brands serv iced by our nine garages together enjoyed a market share of about 40% of German new pa ssenger-car registrations (KBA 2001 - German Federal Office of Motor Transport ). Their share in the registration of new v ehicles fitted ex-works with an air-conditioning system was somewhat higher, being just under 50% by my own estimation. The reason for this is the traditionally higher rate of air-conditioning system installation in German cars as compared with imported brands, which make up a third of new registrations.



### 5. Recovery/recharging stations employed

All of the recovery/recharging st ations employed for recovery and charging purposes had been manufactured during the period 1991 to 1996, so none of them were of the very latest design. The four different types used were

the SECUmat 134 by Behr: five units in five garages; the FAST 2000 by Fischer: four units in two garages; the RHS 850 by Waeco-A Gramkow: one unit in one garage, and the Robinair Vacumaster by Robinair: one unit in one garage.

One garage has been using a Beissbarth MAC 26 instead of the SECUmat 134a since May 2001, but this unit had not yet been entered on the Record Sheets.



### 6. First stage of quantity correction - the 1,004 documented cases

Total number of entries from 1999 to 2001: 1,0043

The number of entries in the Record Sheets for full years 1999, 2000 and 2000/2001 amounted to 1,004 in total. There were a further 209 entries from the previous period, which served as control indicating whether a vehicle may already have had its air- conditioning system opened, and if so, under what

conditions. 1

The 1,004 generally analysable entries on the opening of air-conditioning systems in the years 1999 to 2001 were distributed more or less uniformly over the three different car brands - Brand 1: 253, Brand 2: 317, Brand 3: 434.

Different air-conditioning systems having deducted duplicated entries: 932

Of the 1,004 entries, registration numbers duly iden tified vehicle air-conditi oning systems that had been opened several times in the course of one or two years. 2 There were 72 duplicated entries in total, so

the number of different air-conditioning systems effectively opened in 1999 to 2001 reduces to 932.

Ex-works R-134a systems - ex cluding R-12 conversions: 875

As a rule, mechanics expressly entered as such any conversions they made from R-12 to R-134a. (The list of old vehicles, which is to say vehicles not having an original ex-works R-134a air-conditioning system, was completed at a later stage with refere nce to the date of first registration and the type of vehicle). Reduced by the total of 57 system-op enings effected for conversion or sometimes for retrofitting purposes during the period early 1999 to mid 2001, the number of different vehicles having ex-works R-134a air-conditioning systems and docu mented in the Record Sheets for 1999 to 2001 amounts to 875 (Brand 1: 216, Brand 2: 284, Brand 3: 375).

Ex-works R-134a systems excluding commercial vehicles: 841

One garage also opened and recorded the air-c onditioning systems of commercial vehicles. The 34 cases in question having been duly identified and left out of the equation, the total number of genuinely passenger-car air-conditioni ng systems comes to 841.

Average charge quantities and losses - 841 pa ssenger-car air-conditioning systems

The average charge quantity for all (841) air-conditi oning systems was 856 grams. Differences of up to

30% were to be found between the individual brands - Brand 1: 734 g, Brand 2: 857 g, and Brand 3: 932

g.

The average loss of refrigerant determined per air- conditioning system opened was 546 grams, or 64% of the charge quantity. Here again, there were diffe rences between the brands - Brand 1: 54%, Brand 2: 70%, Brand 3: 64%.

The total volume of refrigerant lost from the 841 systems amounted to 459.2 kilograms.

1 Only very limited use could be made of another 337 ent ries documenting all of year 2000 at one further garage (a tenth) associated with a fourth German ma nufacturer, because a figure of "1000 g" refrigerant (recovery/recharge) had been entered without exception for every vehicle serviced.

2 Such cases often involved accidents, where the refrigerant was just recovered before bodywork repairs, and then just charged again after the repair work (several days later). The two entries related here to one and the same instance of damage. Oc casionally, when first coming into the workshop, a system was charged with addition of contrast m edium but the leak was not eliminated. Then on a second visit, the leak was finally rectified thanks to the contrast medium. Here again, the two entries

relate to one and the same case.4



### 7. Second stage of quantity correction - the 841 analysable cases

The age of a vehicle on its visit to the workshop is of decisive importance to certain aspects of the present study's investigations, especially the determina tion of so-called 'normal' emission, but this age is

not entered in the Record Sheets.

In a second stage of our work, the nine garages were asked, through their service managers or through their environmental protection offi cers, to examine their duly retained workshop records and provide the following three extra items of data on each vehicl e identifiable by workshop date and car registration

number:

1. type of vehicle, 2. date of first registration, and 3. kilometre reading at time of workshop visit.

At this point I would like to thank all nine garag es for completing this time-consuming task, some extending it to one year, but some again covering thr ee. In addition to which I must say that the airconditioning mechanic and/or electrical foreman in each garage showed great patience in answering my queries and providing me with technical information.

"Fully identified" vehicles out of the 841: 678

Of the 841 disparate passenger-cars having ex-works R-134a air-condi tioning systems, 102 could not be identified mainly because they had been deleted fr om the garage records. Deletions are generally effected in connection with transfers of ownership, in other words after a vehicle has been sold by the customer and has had its registration plate changed ac cordingly. The quota of deletions associated with dismantling is not very significant to date.

I decided not to seek further identification of another 61 vehicles (all from record-year 1999 and all recording 'total' loss of refrigerant) by the garage concerned, because the additional knowledge thereby obtained for the purposes of the pr esent study would have been disproportionate to the major work of research otherwise imposed.

In the final outcome, the study disposed of 678 fully identifiable vehicles whose air-conditioning system had been opened between 1999 and 2001: 188 from Brand 1, 252 from Brand 2 and 238 from Brand 3 (along with another 50 vehicles from the year 1998).

At 62.5%, the rate of emission for the 678 "fully i dentified" passenger-cars wa s slightly lower than the 64% for the 841 vehicles listed above. The charge quantities in their 678 systems were also somewhat lower, being on average 848 grams instead of 856 grams.

Average age of vehicle on first opening of air-conditioning system: 34 months

The average age of a vehicle on first visiting a work shop to have its air-conditioning system opened was 34 months, where the relevant information was ava ilable. This figure varies, being 32 months for Brand 1, 31 months for Brand 2, and 38 months for Brand 3. The greater age for Brand 3 is quite conspicuous. That brand was distinctly higher than the others in kilometre reading too.

Average kilometre reading on first opening of air-conditioning system: 74,400 km

The average kilometre reading at time of first visi t to workshop to have the air-conditioning system opened was 74,400 km. Brand 1 clocked in at just under 71,000 km, Brand 2 coming clearly below that with 60,200 km. Brand 3, on the other hand, was well above, with a reading of 92,300 km.5



### 8. Other information from the garages and the car manufacturers

The ga rag e s provide d furth e r data for so me of our inv e stigatio ns (t hose into the "irreg u la r", damage

indu ced p r op ortion of the refrige r ant emi ssi on rate ), for instan ce the i r annu al num ber of vehicl e throug hput s a nd inspe c tion s. Apart from lists of the sta ndard ch arge quantit ies for air-con d itioni ng system s in sp ecific vehi cle s , the Germ a n car m anufa c tu re rs also sent me the ra te of installation of aircon d itioning systems in spe c ific types of passe nge r-ca rs sold an nua lly on the German market since

1992. Thi s extra data is ex pre ssly referred to in Cha p t er E of the prese n t study - whe r e it is dul y applied

- s o there is no c a ll to examine it any further at this point.



### 9. Workshop visits for opening of air-conditioning s y ste m distributed over individual

months

One impo rtan t aspe ct affecting accuracy in measu r i n g the rate of re frigerant emission that ou g h t to be introduced in this initial chapter (e sp eci a l l y since it alre ady arises o u t of the garag e Re cord She e ts before they were ' c orre cted ' - whe r e they extend to co ver a full twelve-m onth p e ri od, that is) is the likely

distrib u tion of air-con d iti oni ng-system o p ening s over ti me (by the m onth) withi n a calen dar yea r , as identified by the date ente r ed for wo rksh op visit.



### W o r ksh o p V i sits to o p e n A i r
- Co n d itio n i n g S y stem b y M o n t h in

Y ear (1,212 v e h i cles = 100% )

3% 4% 5% 6% 16%

12% 12%

8%

5% 4% 2% 23%



### 0% 5% 1 0 % 1 5 % 20% 25%

J a n F eb M a r A pr M a i J un J u l A ug Sep O k t N o v D ez 

### Mo nt hWorkshop Visits

Diag ram 1: Worksh op visits to open air-conditionin g sy stem, distri bu ted by mont h over cal end ar year. Based o n 1,2 12 entrie s fro m ten gara g e s . The diag ra m sho w s a si gnifica nt accu mulation in th e warmer months of the year (May to August ) and a distin ct und er-rep re se nta t ion durin g the cold er mo nths from

Octob e r to April. (We we re also a b le to use the data from the tenth gara ge - fo urth brand of car - for this

grap h).

Diag ram 1 sh ows a sig n ificant con c e n tra t ion over t he hot months of the year (Ma y to August), and a

clea r und er-repre s e n tation in the colde r months from Oc tober to April. Almos t 25% of all aircon d itioning -system o peni ngs a r e effect ed in May, this after only 6 % in April.6

Rather than reflecting any correspondingly more frequent occurrence of defects in air-conditioning systems in May, this lack of uniformity in distributio n is far more likely to represent the more frequent perception of defects during the warmer time of year. Ev en where a defect might in fact be noticed in the colder months of the year, it apparently fails to consti tute a disturbance until cooling is called for in the

hotter months.

In the context of determining the rate of emission, this finding demonstrates that the time at which

emission occurs does not coincide with the time at which it is examined and eliminated in the workshop, in fact several months may pass by between an actual loss of refrigerant and its entry in a Record Sheet. Since, in the following, a vehicle's age is defin ed as the period elapsing from its first registration to its recorded visit to a workshop (the date entered in the Record Sheet), our figures are systematically overstated; not just because of the time it take s to arrange a workshop visit, which would be a normal factor to take account of, but because the time between occurrence of a refrigerant loss and its detection in the workshop is probably a great deal lo nger still. Clearly, I have been unable to correct this overstatement of age in any single instance.

Accordingly, it should be duly borne in mind in exam ining this study that the recorded age of vehicles has been systematically overstated - by about two or three months in my own estimation.7



## B. Reliability of Records and A ccuracy of Recovery/Recharging

Stations

The quantities of refrigerant which mechanics ente r in their Record Sheets as duly recovered and recharged by the recovery/recharging station are of de cisive importance to this study. It is even more important to know how accurate these records are, wh ich is to say how close a mechanic's entry may, or can, come to the actual quantities in question. In th is connection, it is often impossible to distinguish between objective factors such as the technical char acteristics of the recove ry/recharging station, and subjective factors like the mechanic's accuracy in operating and reading off the unit. Consequently, our study sets out below to

• explain the recovery and charging process of a typical recovery/recharging station (taking the SECUmat 134 by Behr as example) by describing its four main phases with reference to a drawing;

• discuss errors in determination of quantity, their significance, and their possible correction, and finally

• estimate refrigerant losses in so far as caused by the servicing operation itself.



### I. Recovery and Charging by Recovery/ Recharging Station (see drawing)

The reader is recommended to refer to the drawing overleaf to assist with understanding the individual stages of the recovery an d charging process.



### 1. Recovery (2 to 5 minutes)

The service connections of an ai r-conditioning system (see detail at bottom right) in a vehicle are arranged upstream of the compressor (grey 1) on t he low-pressure side and upstream of the expansion valve - often on the dryer - on the high-pressure si de (grey 2). The low-pressure hose (1) and the highpressure hose (2) of the recovery station are jo ined to these service connections. The valves are opened by manually turning the cock on the quick-fi tting pipe union duly attached. The air-conditioning system's low pressure (suction pressure) and high pres sure (liquefying pressure) readings are displayed on the pressure gauges (5) provided. Both operating points (or just the high-pressure point where a controlled-output compressor is installed - because low pressure remains unaltered in that case at 2 bar) provide the first indication of a system's condition.

The two hoses are joined together by valve taps (3 an d 4), so the refrigerant passes over a single main line leading inside the recovery/recharging station (t he set of pressure gauges and the main line are usually inside the station, just the service hoses being connected on the outside). The refrigerant is drawn in by the compressor (K) and flows over the separator (6) which holds back any entrained refrigerant oil. All of the refrigerant is rendered gase ous by absorption of heat by this stage at the latest, to prevent the compressor from being damaged by liq uid. The compressed gaseous refrigerant is cooled in the condenser (7) and then liquefied again, after wh ich it flows through the filter dryer (8) into the collecting tank (9).

In the region of 10 to 20 grams of refrigerant ma y still be left to evaporate inside the air-conditioning system after the first recovery (tak ing about 2 minutes), for instance re frigerant dissolved in oil or other liquid refrigerant which could come from the dryer, for example. This subs equent evaporation increases pressure in the system to over 0.6 bar, which ca uses renewed recovery from the compressor when8

operating aut omatically. O peratin g man ually, the mech a n ic sho u ld wait briefly and must then himself

swit ch on to recove r the su bse que ntly evaporate d ma terial.

The air-condit i oning system is open ed for repai r wo rk. As altern ative, the internal refrige r ant-cle aning

prog ram can be run b e fore hand, in a cy cle drive n by the comp re ssor thro ugh col l ecting tan k (9),

sep a rato r (6 ), cond en ser (7 ), filter dryer (8 ) and b a ck to the colle ctin g tank (9) ag ain.

Fig. 1: Typica l recove ry/re c hargi ng statio n for pa sse ng er-ca r air-con d itioning syst ems - (1) lo w-pre s sure hose co nne ct ion; (2) hi gh-pre s sure ho se con n e c tion; (3) an d (4 ) valve co cks; (5 ) pre s sure ga uge dial s; (6) oil sep a rat o r or tr ap; (7 ) con den se r; (8 ) filter dry e r; ( 9 ) re se rv oir t ank; (1 0) (11 ) (12) sole noid v a lv es; (P) v a c uum p u mp; (K) c o m p re ss or. Bottom right: co m p re ssor, cond enser an d f ilter-drye r of ca r aircon d itioning system. Grey (1) and (2): lo w-p r e s sure a nd high -p re ssure ai r-con d itioning -sy s tem service

con n e c tion s. (Source: Dai m lerChry s le r 2001 - m odifi ed).9



### 2. Evacuation (20 to 30 minutes)

The hoses of the recovery/recharging station are connected to the air- conditioning system. The line to the vacuum pump (P) is cleared by closing solenoid-valve (10) and opening solenoid valve (11) inside the recovery/recharging station. The pump sucks in the air and other non-condensable gases from the system, and the vacuum gradually pr oduced in the process boils and draws out any moisture which may be present. Waste air is blown into the atmosphere, wh ile low pressure develops in the system at the same as required condition for charging.

The leak test by vacuum ('vacuum check') is pass ed where the pressure-gauge dials (5) fail to display any readable rise in system pressure for at least five minutes after the vacuum pump has been turned

off.



### 3. Recharging (1 to 3 minutes)

The low-pressure side (1) and high-pressure side (2) of the air-conditioning system are connected to the recharging station. The valve cock (3) on the lo w-pressure side is closed before charging, because liquid refrigerant must not be allowed to flow in ups tream of the compressor. The valve cock (4) on the high-pressure side remains open. To make sure the re frigerant circuit is sufficiently well charged, the refrigerant in the reservoir tank of the recharging station is warmed by a heater to between 25 and 30°C, which increases the pressure in the tank to about 7 bar.

Liquid refrigerant flows into the system on the high-pressure side while the charging valve (12) remains open. The fill level on the transparent reservoir tank (9) falls as the tank contents flow out, so the amount of refrigerant discharged can be visually ch ecked while recharging proceeds by reading off the measuring lines encompassing the tank at 50-gram intervals (show volume converted to weight and allow for temperature-induced expansion).

Instead of employing the pressure method, some stati ons use an additional electrical charging pump for charging purposes (this is actually essential wh en charging large quantities). Some old and all more recent stations permit charge quantities to be read of f precisely to within one gram, being equipped with an electronic scale for the reservoir cylinder rather than a visual control system.



### 4. Emptying the recharging hose

Pressure in the air-conditioning system rises as t he charging operation proceeds, which stops the hose and pressure-gauge fittings from being entirely emptied of refrigerant. The hose's quick-fitting pipe union closes when the service connection is taken off, to prevent loss of refrigerant from the incompletely emptied hose and to stop air or damp from getting in to it (an estimated quantity of just 1 to 3 grams of refrigerant evaporates with a hiss between service valve and the interior of the hose's quick-fitting pipe union.)

The hose is emptied by suction by turning on the co mpressor again. Up to 50 grams of refrigerant may still remain in the hose depending on its length and on the internal temperature of the air-conditioning system. This residue is emptied for labour safety reasons among others, becau se even the safest of closure systems would be unable to ru le out the possibility of a minor flash of refrigerant (engendering the risk of localised frostbite) when manually attaching a full hose during the next recovery operation.10



### II. Errors in determining Quantity; their Significance and Correction

1. Rounding off when measuring by sight, also where weighing electronically

All modern and some older stations (made betw een 1990 and 1995) have an electronic scale for the reservoir tank which determines quant ities duly recovered and recharged. The scale displays changes in the tank's weight digitally and therefore precisel y to within a gram. Three of our nine garages had stations of this kind, two of them using the FAST 2000 (manufactured between 1990 and 1994) and one having the Robinair Vacumaster (made in 1996). With the FAST 2000, the mechanic has to calculate the recovery volume himself by reckoning the differe nce in reservoir-tank (cylinder) weight before and after the operation (e.g. 5,329 related to 4,803 gram s). The Robinair station displays the recovery volume as an absolute figure related to zero. When charging - regarded as the more important operation - the mechanic can enter the desired dosage to within exactly one gram in all three stations, e.g. 1,000 grams, this dosage then being let precisely out of t he reservoir tank (cylinder) along with the addition of a compensatory excess quantity.

The reservoir tank simultaneously serv es as (transparent) measuring cy linder in the other most widely used types of station (SECUmat 134 or Waeco RHS 850). When recovering and recharging, the mechanic watches the measuring lines encompassing the cylinder at 50-gram intervals. The charge quantity cannot be read off from zero, but, like the reco very volume, as difference in level before and after the operation, so not only does the mechanic have to do mental arithmetic, he must also have a good eye. In practice, he usually marks the starting level on the outside of the measuring cylinder (using a felt pen) and thus reduces the risk of read-out errors.

The Record Sheets furnish no proof that stations with scales and electronic display might be in any way superior to those simply provided with visual cont rol means, all hand-written entries (also those entered manually into a computer, as done at one garage) being made in 50-gram increments.

This is not particularly surprising in respect of charging . Almost all air-conditioning systems in German cars work with standard quantities stated within 50 or 100 gram limits, with 25 or indeed 10 gram limits rarely to be found. This is also the case with fo reign makes (see Autodata 2000; Waeco 4/2000). So if the mechanic knows the standard charge quantity, why should he do otherwise than simply enter it along with the extra allowance for the hose? 3

However, the 50-gram increment which both types of station use for entries seems astonishing at first glance in respect of the recovery quantity , because (but for a few except ions) the recorded quantities must necessarily be based on figures duly rounded up or down - although it is easy to see why this method is used for measurement cylinders having 50-gram increments. With even the very best of visual inspection, a deviation of up to 25 grams fr om the effective quantity would be normal. As opposed to this, the electronic scale provides data precise to within one gram. Where not measured in relation to zero, the displayed weight of the reservoir tank should be noted down beforehand (on paper or pocket calculator) - if the weight is 4,803 grams before recovery, and t hen 5,329 afterwards, producing a difference of 526 grams, the mechanic will enter ei ther 500 grams or 550 grams. However, he would also enter 500 grams for a figure of just 478. T he inaccuracy of measurement amounts to about 50 grams (25 grams up or 25 grams down). Where 200 grams of refrigerant is lost, this deviation makes up more than ten percent. Greater precision would take the mechanic more time and is not required of him. The same procedure is followed even in the garage operating a Robinair station (recovery displayed to a precision of one gram), where the Record Sheets also document none other than 50-gram increments.

3 A station's accuracy of measurement when ch arging is not all that important to the present study in any case, the factory standard figure duly being take n as basis for a full air-conditioning system.11

In all 841 cases covered by this study, the loss of refrigerant is determined as difference between the

ex-works standard charge and the reco very quantity entered by the mechanic. From practical experience, there is no significant difference in the accuracy of en tering recovered quantities measured by eye or by electronic display, both measurement s, as we have said, being duly rounded off to 50

grams. 4 Given the mechanic's routine, there is little reason to think of the entries based on electronic measurement as being any more reliabl e than those made with the naked eye.

The foregoing has the consequence for the present study that the entries it records may generally incorporate a deviation of about 25 grams up or down from the effective quantity recovered . The only exception would be the 323 entries of 'total' loss of refrigerant (repres enting a recovery of zero grams), where rounding-off is less likely. Taken together, howev er, 'total' losses do make up almost forty percent

of all 841 entries.



### 2. The residue in the hose as source of error in determining the charge quantity

As mentioned at the end of the description of t he charging operation, the charging hose never empties entirely into the air-conditioning system. Were t he mechanic simply to read off the exact standard charge from the charging cylinder, he would be systematically under-cha rging the systems he works on. As a result, some car manufacturers specify an 'over-dosage' of from 25 to 50 grams by way of compensation. This recommended extra quantity is also advised by the suppliers of recovery/recharging stations, into some of which the extra quantity can be permanently programmed as a function of the length of the recovery and recharging hoses. The advant age here is that the mechanic can still stay with

the exact standard system charge.

2.1 Quantity recovered occasionally exaggerated because hose not emptied.

After charging, the mechanic must always make sure to have any residue sucked back out of the hose. If he forgets to do so, then when he connects up the unemptied hose to perform the next recovery, he risks frost-bitten hands from a flash of refrigerant ga s even if only a little emerges from the closure. The important aspect in the present context is that t he quantity of refrigerant recovered with an unemptied hose of this kind would then be greater than the actual content of the air-conditioning system - resulting in an "upward" error in measuring the quantity reco vered. This measurement error was mentioned in the course of interviews with air-conditioning me chanics during the present study, its "occasional" occurrence being justified on the grounds of pressure of work associated with payment of an incentive

wage.

2.2 Charge quantities entered in Record Sheets often deviate from standard charge

Whether or not the excess quantity is 'sucked back', the calculated extra quantity charged is actually more important to the exercise of determining quant ities than occasional exaggerations attributable to recovery using an unemptied high-pressure hose. Where a car manufacturer indicates "plus 50 grams" along with his type-specific charge quantity, mechanics tend always to let this greater quantity out of the reservoir tank and to enter it as 'charge quantity' in their Refrigerant Record Sheet. Understandably, the quantity 'sucked back' after charging is not measured, so it is not subtracted again from the quantity

4 The latest stations with data interface to the workshop computer and/or integrated printers (for instance, the Beissbarth MAC 26 or Waeco RHS 800 in use with one garage since May 2001) save or directly provide recovered and char ged quantities of refrigerant in 5-gram increments. As these types become more widespread, the accuracy of the data obtained should improve.12

delivered. For this reason, the charge entered is in very many cases not the same as the standard charge of the air-conditioning system, it is in fact greater than same.

The Record Sheets clearly indicate that workshops with stations compelling the mechanic to enter the additional quantity himself on every occasion (this being the case with six out of the nine) enter higher charge quantities - and therefore greater charge differences - than workshops where the extra quantity is permanently pre-set. The latter workshops can work directly with the lower charge quantity. In our own study's case, in fact, the air-conditioning syst ems of vehicle makes whos e charge quantities are specified precisely to within a gram for every model, therefore without compensatory addition, are recovered and charged exclusively with stations in which excess quantity of refrigerant is permanently pre-programmed.

The consequence for the present study is that the differences between recovery and recharging that are duly entered in the Record Sheets cannot always be taken as actual refrigerant loss from the vehicles in question. Corrections may sometimes be necessary. Refrigerant loss in the present case generally comprises the difference between entered recovery and the manufacturer's specified standard charge, whether or not the latter is actually entered as charge in the Record Sheet

.

The varying data specific to particular vehicles and also to years of manufacture is gleaned from lists provided by the three car manufacturers and from the literature on the subj ect (Autodata 2000; Waeco 4/2000), an approach which I think should reduce the incidence of measurement errors. At any rate, the present study is concerned with refrigerant loss determined on the occasion of an air-conditioning system's f irst visit to the workshop since first registration. For this reason too, t he 'ex-works charge' is a better measure to go by than the 'workshop charge' - after all, it can readily be assumed that no car manufacturer is likely to fill his systems with any more refrigerant than absolutely necessary.



### 3. Temperature differences between recovery/recharging station and air-conditioning system when recovering

Another possible source of error relating not to the charge quantity, but to the recovery quantity - one that may arise in connection with all designs of recovery/recharging station - is discussed in the following for the sake of completeness.

The only propelling force transporting the refrigerant th roughout the recovery and charging operation is the compressor in the recovery/rec harging station. Not only does the compressor suck the refrigerant out of the air-conditioning system and force it into t he condenser, it is also the only agent causing the refrigerant already disposed in the liquids pipeline downstream of the condenser to flow on into the reservoir tank, in that liquid continues flowing ou t of the condenser thanks to the workings of the compressor. As soon as this flow peters out (once the system is sucked empty), the refrigerant remains stationary in the final stretch between condenser (7) a nd collecting vessel (9). Measurement errors do not generally arise in this connection, since when recovering the next air-conditioning system, this residue originating from the preceding system, downst ream of the condenser in the recovery/recharging station, is in fact the first material carried into the reservoir tank. Not until that operation is completed does refrigerant begin to flow in from the system currently under recovery, once again minus the residue downstream of the condenser, and so on and so forth.

In principle, the incomplete throughput of the one recovery is continuously compensated in this manner by the likewise incomplete throughput of the next recovery. Distortions only occur in connection with temperature differences and therefore differences in expansion between in-flowing new refrigerant and old refrigerant - which distortions, not having been examined in the present study, have not been taken

into account.13



### 4. Recovery of after-evaporation forgotten

We explained when describing the basic operation of re covery that, after the first recovery taking about two minutes, approximately 10 to 20 grams of refrigerant (which may have been dissolved in oil, or was not immediately withdrawn from the lower parts of the refrigerant circuit) may still evaporate within a system which is not yet completely empty. In autom atic operation, which is a facility of all of the recovery/recharging stations in the present population, the recovery process is set up to extend for at least an extra three minutes, so that, after the station is turned off for the first time, it will start again on any renewed rise in pressure in the air-conditioni ng system and then continue with the recovery of

residues.

In manual operation, the mechanic must wait for any possible rise in pressure after the first recovery (observing the pressure gauges), and then turn on the station again where necessary.

Clearly, this after-evaporation may well be neglected fr om time to time under general pressure of work. Any subsequently evaporating refrigerant of this kind is noticeable as emerging cloud by no later than the stage of opening the air-conditioning system. In such cases, the recovery quantity read off the recovery/recharging station understates the cont ent of the system by from 10 to 20 grams.

This study has not attempted to quantify the differences in measurement attributable to this neglect of after-evaporation (and thus the emission of refrigerant due to improper servicing). I also felt unable to give any estimates, in fact all I would say is that six of the nine stations did provide the option of manually terminating the recovery period.



### 5. Omitted entries

In concluding our discussion of sources of error in determining refrigerant quantities when servicing an air-conditioning system, we should mention the mistake that actually occurs most frequently: unintentional neglect to enter the recovery and charging operation in the Record Sheet.

Although the Refrigerant Record Sheet is usually kept in the workshop, in a folder directly attached to the recovery/recycling station, it is inevitable that hand-written reco rds of this or that operation can sometimes be forgotten in the general hustle and bust le of everyday garage routine. Then looking at the Record Sheets themselves, there is no need to be a handwriting expert to see quite clearly the sometimes unusually careful and identical writing of one and the same mechanic, using one and the same ball point, as he attempts to catch up on the entries that should have been made for a number of vehicles over the past three or four days. Then again, it should be said, this 'catching up' is not always

done.

Air-conditioning mechanics interviewed in the course of our study gave estimates of forgotten entries ranging from "none at all" in smaller garages, to "at l east ten percent" in the larger firms. Although I think myself that the mean of 5% is too low, it has bee n taken as the maximum in this study. Which means that refrigerant losses in the region of 477.2 kilo grams should be regarded as 5% or 24 kilograms higher than that in reality, amounting, in other words, to about 500 kilograms (501 kg). The loss per vehicle does not alter as a result, because this allowance al so increases the number of air-conditioning systems by 5%, from 841 to 883.

This correcting factor produces a slight increase in determination of the so-called 'irregular' rate of emission (see Chapters E and F), while the 'regul ar' rate of emission (see Chapter D) remains

unaffected.14



### III. Refrigerant Loss caused by the Servicing Operation itself

Apart from neglected after-evaporation, two other sources of refrigerant emission associated with servicing would be loss while locating leaks, and loss when detaching the charging hose.



### 1. Loss when charging

The maximum loss on detaching the charging hose from the service connection (see description of basic process) is estimated at between one and three gr ams. The hose end closes of itself as it is withdrawn from the service valve (t he coupling cannot be removed unless the cut-off valve is closed by hand), this being a major technical improvement ov er the period before 1991, when refrigerant R-12 was generally released entirely into the atmosphere on opening an air-conditioning system. According to the suppliers of recovery/recharging stations, the reliabilit y of this closure system has to a large extent been technically perfected by now, so the mean loss estimated at two grams would be regarded as unavoidable at the present time (Recovery/Recy cling/Recharging Stations Conference - 2001).

Since, when we subtract 31 renewed charges not effe cted (including vehicles sent for dismantling) and then add the 72 multiple charges in the same or the succeeding year (in so far as recorded in both situations), the 841 different air-conditioning systems in our survey population would in fact have been charged 882 times in total, 882 times two grams or in total just under two kilograms of refrigerant being released into the ambient air in the process.

To put it another way, loss during charging adds tw o grams or 0.4% to the mean loss of 546 grams (64% in relation to the mean charge quantity of 856 grams) recorded for all opened air-conditioning systems in the study population, so we end up with a total of 548 grams.



### 2. Refrigerant loss when locating leaks with contrast medium

The 'total' losses we referred to above extend not onl y to air-conditioning systems 'irregularly' harmed by outside influences (the main category being 'accident damage') and usually producing 100% emission, but also include vehicles having losses of over 100%. These are cars which, due to the one leak, have lost refrigerant in the course of more than one charging operation, becaus e instead of being repaired during the first visit to the workshop, the leaking system was simply filled up. 29 of the 323 recorded 'total' losses come under this heading.

Where the mechanic fails to find a fault in an empty system on visual inspection or on performing the vacuum check after recovery, he contin ues by filling the system with liquid nitrogen or with refrigerant to localise the leak, observing the pressure-producing gas that duly emerges. To find the leak, he uses an

electronic leak indicator unit which reac ts to refrigerant escaping from t he system either in pure form or (where flushing with liquid nitrogen) as entrai ned residue. Although not yet generally approved by compressor manufacturers as a method of locating leaks 5 , it is normal practice in many garages to add a contrast medium or 'tracer' when charging the refrigerant. The tracer comprises a few drops of refrigerator oil mixed and dyed with a fluorescent s ubstance and incorporated with the in-flowing charge of refrigerant. This method is used in eight of the nine garages in our population. 6

5 The principal reason for their reluctance is concer n that the tracer might damage the compressor. One thing that can definitely be said, however, is that t he tracer dissolves in oil, not in refrigerant. The refrigerant sucked in by the recovery/recharging stat ion's compressor is colourless when it reaches the

reservoir tank.

6 Obviously, pressure-based leak testing with nitr ogen is a more environmentally friendly method of detecting leaks than charging with refrigerant and contrast medium. One of the nine garages does not15

Having allowed the air-conditioning system to run for a few minutes, an ultraviolet lamp will usually

locate the tracer as luminous coloured stain around th e leak (since a case of this kind involves renewed emergence of refrigerant, loss from the vehicle in question rises to more than 100%). The stain is generally cleaned off after the leak has been repaired, to prevent any misunderstanding the next time the car is maintained (any residue left behind mi ght otherwise be interpreted as a new leak).

If, even where using a tracer, the mech anic still fails to find a suspected leak on the same day, the leak may be regarded as active but minute, only allowing the associated volume of refrigerant to escape over a prolonged period under real driving conditions, so its location by staining may take days or weeks of further operation. The fault will not then be found an d rectified until the next time the car visits the workshop. This method of leak detection is associat ed with emission rates of 200% - apart from the few vehicles (only two in the present population) that had different leaks in the one year.

Refrigerant loss occurring over and above 'total' lo ss where a leak is not found but on emergence of tracer-containing refrigerant (whether this happens on the first visit or during a subsequent visit to the workshop) is regarded in this study as 'service-induced' emission associated with leak location. The 29 affected vehicles in the study population suffered an extra loss of 20.5 kilograms in addition to their (first) 'total' loss of 27.5 kilograms. These 20.5 extra kilograms are 's ervice' emissions in the narrower

sense of the word.

Accordingly, of the total recorded refrigerant loss of 459.2 kilograms from the 8 41 vehicles in the study, 20.5 kilograms (or 4.5%) is attributabl e to loss during leak detection.

Other, rather more 'unusual' losses of refrigerant in the workshop should also be mentioned at this point. For example, one 1997 Record Sheet from one garage documents total leakage from the tank of the recovery/recharging station ("charge 25 kg, recove ry/recharging station leaking"). The refrigerant released over night in this case more or less equalled the above 29 cases of 'service' emission in the course of leak detection (20.5 kg in eight garages).

use tracer to locate leaks, with successful results according to the Record Sheets, in that none of them include any entry of multiple visits because of one and the same leak.16



## C. Reasons for Opening an Air-Conditioning Sy stem and Causes of

Detected Refrigerant Loss

Picture: DaimlerCh r ysle r 2001 (modifi ed)



### Fig. 2: Potentiall y defe c tive components of a passenger-car air-conditioning sy stem*

1. Comp re ssor, 2. High-pressure line (ga s e ous) to con d e n se r, 3. Cond en ser, 4. High-pressure line (liqui d) to drye r, 5. Dryer/ colle ctor (with hig h -p re ssure a nd low-p r e s sure switche s ), 6. High-pressure line (liqui d) to expan si on valve, 7. Evaporator, 8. Expansion valve for evaporato r

, 9. Suction lin e (ga s eo us) to comp re ssor,

A. Service co nne ction on h i gh-p r e s sure side,

B. Service co nne ction on l o w-pressu re side.

* Evaporato r injectio n throu gh expan sio n valve, not through o r ifice t ube. If using orifice tub e s t he

colle ctor ("accumul a tor" ) is down s tre a m of the ev aporator to en sure the tran sformation of all the refrig era n t into gaseou s st ate before e n t ering the co mpre ssor.17

The Record Sheets document the refrigerant whic h a mechanic recovers from each vehicle (having opened its air-conditioning system) and measures with varying degrees of accuracy. Any shortage of refrigerant discovered on opening is therefore recor ded at the same time, as difference between the quantity recovered and the standard level of charge. T he rates of loss determined in this manner cover the whole spectrum from 0% to 100% (and sometime s above). While the expl anation provided by the air-conditioning mechanic is not always that informat ive, the proportion of precisely recorded cases is sufficient in size to provide a picture of the pr incipal reasons for opening an air-conditioning system.

In Table 1, all recorded rates of refrigerant loss are separated into small, medium and large volumes. The percentages of these losses out of all opened ai r-conditioning systems is shown in Column 2, their percentage of total refrigerant loss in Column 3.

Table 1: Percentage of small, me dium and large refrigerant loss within total loss of 459.2 kg (841 systems)

Refrigerant loss Percentage of all opened systems Percentage of total refrigerant loss

small - less than 40% 39% 9%

medium - 40% to < 100% 23% 24% large - 100% and over* 38% 67% * Losses > 100% are attributable to multiple lo sses from the one system in the same year

Small losses (less than 40%) were found in about 40 % of air-conditioning systems opened. This group's percentage of total refrigerant loss is just 9%. 'Total' losses of 100% and above represent the other extreme, also found in nearly 40% of opened air-condi tioning systems but making up two thirds of total recorded refrigerant loss (see bottom line of Table 1).



### I. Elimination of Leaks, the Main Reason for Opening on Total Loss of Refrigerant

Total loss of refrigerant results in failure of the air-conditioning syst em. Even before 'total' loss actually occurs, however, the system will already have come to a standstill when there is only about 100 to 200 grams left in its circuit. This is because extreme la ck of refrigerant drops the system's high-pressure below about 2 bar (the setpoint value), on which the co mpressor is automatically switched off either by a special low-pressure switch, or by an internal control system. If there is too little pressure, the refrigerant will even begin to evaporate below zero degrees cent igrade, causing the system to ice up. The compressor itself needs to be protected against ru nning hot or clogging up, because lubricant also ceases to circulate once the refrig erant runs out. The driver himself w ill usually notice and report his airconditioning system's lack of performance, nor can any such lack escape routine workshop-inspection using an electronic fault readout unit, which will register the fact that the compre ssor is switched off. For the mechanic, lack of refrigerant is the obvious di agnosis inducing him to start recovery with the recovery/recharging station so as to find and repair a leak in the system.

Air-conditioning systems suffering total loss of re frigerant are generally opened for one single reason, namely to remedy the cause of this particular kind of loss. That is the main reason. Which seems an obvious and trivial thing to say, but it isn't in fa ct, because the same does not apply to air-conditioning systems experiencing losses of less than 40%.

The cause of a total loss is mainly external, but can also be internal.

The cause is external where mechanical action from outside produces leaks in components of the refrigerant circuit. Such action would be an accident damaging the front panelling, or the impact of18

stones. The condenser is by far the most likely com ponent to be found leaking where loss is total, being placed well forward on the vehicle, right in front of the radiator.

The cause of a total loss is internal where a component, without being exposed to forceful outside influence, suffers an 'irregular' defect which creates an effective point of emergence for the refrigerant. This would not include normal wear and tear, to wh ich every component is physically prone, but some unusual instance such as a burst or corroded compre ssor, a burst dryer, perforations in the pipeline, cracks in the evaporator, etc. W hat accidents or stone impact on the one hand and irregular component

defects on the other share in common is an emissive pattern of damage.

The three recorded causes of total refrigerant loss were

1. accidents involving body damage (40%), 2. minor collisions, stone impact or internal emissive component defects (40 to 50%), and 3. unknown causes where the vehicle was simply recharged (10 to 15%).



### 1. Empty air-conditioning system after accident involving body damage

Accidents involving severe panel damage in the front region of the vehicle account for around 40% of recorded total losses. In the process, frontally posit ioned components of the ai r-conditioning system are pushed in and caused to leak - generally abruptly. The condenser is damaged in 90% of cases, sometimes the high-pressure lines connected to it too, and the adjacently fitted dryer.

Where an accident damages the body rather than th e bumper, the vehicle is given to the body shop which, in addition to repairing the damaged panels, al so replaces the defective components of the airconditioning system. In such cases, the air-co nditioning mechanic checks the system beforehand to make sure it is empty, then afterwards he chec ks it for leaks and rechar ges it with refrigerant.

The mechanic, completing his Record Sheet, may enter the whole operation in two stages: "Recovery: 0 g, recharge: 0 g" and then some days later - "Recov ery: 0 g, recharge: 1000 g", adding the note "accident" each time. Or, alternatively, he may combine the whole operation into one entry: "Recovery: 0 g, recharge: 1000 g; Note: accident". Normally, he does not name the defective part, because he is not the person replacing it 7

.



### 2. Total loss due to stone impact or irregular component defect

Another 40 or 50% of total losses are attributabl e to leaks caused by a minor collision, an unnoticed knock from a stone, or an unusual component defect . The repair work is not given to the body shop in such instances, but is done by the air-conditioning mechanic himself, who then also makes a record of the replacement of components. Here again, the condenser is a typical source of leakage, albeit that its leaks are mainly caused by stones. A thrown stone des troys the surface of one of the flat refrigerantconducting tubes, which then corrodes (by pitting) at t he point of impact. It takes at most a week for an emissive leak to develop, the process in fact being accelerated by damp or salty air passing through the

condenser.

The Record Sheets would indicate that , at a rate of 40 to 50%, the condenser is the most frequent single cause of total refrigerant loss in the absence of panel damage, so it is also the component most frequently replaced by the ai r-conditioning mechanic himself ; but by no means the only one, of course.

7 The absence of a second entry after the "Recovery: 0 g, recharge: 0 g, Note: accident" entry in the Record Sheet indicates total failure and dismantling of the vehicle - apart from occasions where the second entry may simply be forgotten.19

Table 2 reproduces the order of frequency with whic h components are replaced, in so far as expressly

documented in the Record Sheets (70 instances).

Table 2: Defective components causing total refrigerant loss and replaced by the airconditioning mechanic himself (70 recorded instances - excluding accidents damaging body) Component Percentile share of components replaced by air-conditioning mechanic

Condenser 42% Pipelines 17% Evaporator 17% Expansion valve 9% Compressor 8% Dryer 3%

Seals 4%

A replaced component is only listed here where it has been the prime cause of total loss. It is important to mention this, since some components may be repl aced because of secondary defects. For instance, the dryer, which generally becomes inoperative on ce the air-conditioning system has been running empty for a while. The expansion valve, too, must often be replaced in consequence of some other component defect, in this case a defective compre ssor, whose chips can clog the valve. Piping often needs to be replaced as well, when the component (say the condenser, evaporator, or expansion valve) to which it is connected suffers damage

.

While stone impact and accidents involving a minor collision bear the main responsibility for leaks in condensers (42%), and similarly affe ct the high-pressure refrigerant lines connected to the condenser (17%), leaks in the few other exposed components (41%) are far more rarely caused by outside influences. Where a defective compressor, expansion va lve, dryer, connection or pipeline abruptly lets so much refrigerant through that total loss occurs, the reason is often 'irregular' internal damage, due, for example, to corrosion (including the electrochem ical type), overload (excess pressure), or defective workmanship on the part of the manufacturer. It can also happen that components will be so severely damaged by a preceding lack of refrigerant (insufficien t lubrication of the comp ressor, etc.) that they begin to leak of themselves, letting the very last of the refrigerant finally escape.



### 3. Total loss followed simply by recharging without repair work

Components of the refrigerant circuit are not always actually replaced when t hey leak, even where the work would be technically feasible or had even bee n begun (by adding tracer, for instance). In fact, about 10 to 15% of systems with total loss ar e simply recharged, the main reasons being

• customer failure to have the necessary work done, or to bring their vehicle in on the due date for inspection, hoping they will get by with just a rech arge especially where a leak is thought just to allow a very slow escape of refrigerant;

• risk of renewed total loss after a simple rechar ge being taken, by customers who have to pay for the repair work themselves where out of warranty or not covered by goodwill, given that a recharge costs up to ten times less than a repair;

• customer reluctance to undergo time-consuming re pairs, for instance because they are travelling on business and just want their air-conditioning sy stem "quickly patched up" and running again;20

• cases in which the mechanic simply cannot find a leak and therefore has no option but to recharge the system.

The characteristic shared in common by all "simple recharge" cases is that it proves impossible to identify a mechanical leak and associate it with a par ticular component, as a result of which the Record Sheet shows no record of a component being replaced.



### II. Opening a System where Refr igerant Loss is less than 40%

Every car air-conditioning system (even when switched off) is subject to a certain degree of slow leakage of its permanently pressurised refrigerant through hose unions, compressor seals and connection seals, especially where such parts - like the functional components of the refrigerant circuit themselves - are subject to the irregular movements of engine and vehicle. This "normal" loss has no deleterious effect on operation of the air-conditioni ng system over time, especially in view of the relatively generous margin that exists for continued operation of the system despite some reduction in the original charge of refrigerant.

"Normal" refrigerant leakage has no real long-term in fluence on cooling capacity, at least for as long as exclusively liquid refrigerant continues to leave the collec tor where, normally, gaseous refrigerant from the condenser is finally separated out, and injected by the expansion valve into the evaporator. As is known, the cooling performance of the evaporator relies on the ch ange in phase between liquid and gas. As soon as the refrigerant in the system falls below a certain level, the collector obtains too little liquid from the condenser and then loses its ability to separate saturated gas from the condenser to produce liquid refrigerant. 8 From this point on, gaseous refrigerant ("flash gas") extends up to the expansion valve, as evidenced by the formation of small gas bubbles in the liquid line between collector and expansion valve. 9 The expansion valve is not designed to conduct gaseous refrigerant and ceases to provide the evaporator with a steady supply. The evaporator, for want of liquid refrigerant, can no longer produce its cooling effect. The process proceeds fa irly swiftly once begun, continuing until the system virtually stops delivering co oled air (Haussmann, 2001).

The level of refrigerant loss below which an air-c onditioning system will cease to work is not a fixed quantity. After all, 'cooling' is in the first place a matter of subjective feeling, and in the second place, a system's capacity to continue operating on a given vo lume of refrigerant will depend objectively on its technical design, viz. the capacity of the collector , the length of the liquid pipeline between condenser and expansion valve, etc. Nonethel ess, a rough order of magnitude of "around 40%" can be presumed, which means that in the individual situation, one sy stem might work just as well with a 45% loss as

another one would at 35%.

The "40% mark" standing for low loss of refrigerant is based on the experience of mechanics 10
interviewed in the course of our study, who reported that a level of 60% is the bottom limit above which a passenger-car air-conditioni ng system will still be marginally able to operate sufficiently well unless it contains some other defect (see Chapter D).

8 The process of subcooling the refrigerant to prevent undesirable evaporation also fails in this context, because it can only occur in the liquid p hase. Temperature then begins to rise.

9 In systems having a choke (orifice tube), where t he collector is arranged upstream of the condenser (and after the evaporator), flash gas forms in similar fashion on shortage of refrigerant.

10 The mechanics generally considered that an air-cond itioning system will no longer work normally once it reaches "half its level of refrigerant", but that its performance already begins to fall off so much

beforehand that the driver r eadily notices it is failing.21

As we saw above, air-conditioning systems suffe ring total loss of refrigerant are opened to find and rectify an 'irregular' cause of emission (a leak, so to speak). In contrast, refrig erant losses of less than 40% do not generally give occasion to open the syst em. It is not the goal of vehicle inspection to arrange for "a system to be as full as po ssible". Routine measurements are omitted 11 , especially since the whole volume of refrigerant has to be recovered and recharged for the purpose (there are as yet no other methods of conducting this measurement). As a result, refrigerant loss less than 40% goes unnoticed in the majority of the vehicles passing thro ugh a workshop (unlike the case of 'total' loss).

Despite this, the Refrigerant Record Sheets repo rted 40% of vehicles with opened air-conditioning system as having a rate of loss of less than 40% (see Table 1). The reasons for opening these particular systems are substantially different fr om those associated with 'total loss', however, being four in number:

1. replacement of components not causing refrigerant loss (32%), 2. air-conditioning system hi ndering repairs to engine and cooling system (22%), 3. location of damage and preparatory work in advance of body repairs (24%), and

4. leak tests on customer's or workshop's initiative (30%).

It should be clearly emphasised that these were simply reasons for opening the air-conditioning system,

and not causes of refrigerant loss already perceived - as would in fact be the case on 'total loss'. Although refrigerant loss is always made up when recharging, seeking the ca use is not the primary concern when the loss is only slight.



### 1. Component defects not themselves responsible for release of refrigerant

Component defects adversely affecting operation, unusual behaviour of the air-conditioning system accounted for 32% of recorded recoveries from syst ems which still contained sufficient refrigerant to operate properly (loss being less than 40%). Total failure of the system was exceptional. Fault diagnosis was based here, for instance, on unusual noises (rattling compressor, whistling expansion valve), unpleasant odours (condensed water encouraging deve lopment of bacteria on the evaporator), erratic operation due to constant restarting of the compress or (because of insufficient supply of refrigerant and oil through a clogged refrigerant circuit) or the fan (continuously re-activated by the high-pressure switch due to reduced heat-exchanging capacity of a dirty or clogged condenser), etc. Unlike the 'total loss' defects, component faults of this kind are only indirectly associated with the ti ghtness of the refrigerant circuit, if at all. Such "non-emissive" defects in components replaced by an air-conditioning mechanic are manifestly different from the "emissiv e" component defects causing total loss. 12

Table 3: Percentages of components replaced because defective in systems where

refrigerant loss is < 40% - 48 mentions (compared with 'total loss' percentages*) Replaced component Refrigerant loss < 40% Total loss of refrigerant* Compressor 63% 8% Expansion valve 16% 9% Evaporator 5% 17%

Condenser 5% 42%

Seals 5% 4% Dryer 3% 3% Pipelines 2% 17% * excluding 'total losses' with body damage, wher e the condenser is replaced in 90% of cases.

11 Except for diagnosis of electronic faults, the ai r-conditioning system test on inspection is mostly

limited to a brief manual examination of the flow of co ld air from the evaporator during a test drive with air-conditioning system switched on. Some mechanics br iefly press down the valve of the high-pressure service connection to check the outlet pressure of the refrigerant.

12 See Waeco 3/2000b for summary of most frequent ai r-conditioning-system defects, their causes and their possible remedies.22

The centre and right-hand column of Table 3 show how significantly the list of components replaced where loss of refrigerant is slight differs in order of priority from the series of component defects producing total loss without damage to the bodywork.

The compressor is by far the most frequently replaced of components (64%) where refrigerant loss is low, unlike the 'total loss' situation where the same unit makes up only 8% of replacements. The opposite can be said of the condenser , which only accounts for 5% of component defects associated with less than 40% loss, while it constitutes 42% of defective parts where loss is total (in cases not involving panel damage). Evidently, damage to the compre ssor (defective magnetic clutch, faulty control valve, seizing piston, penetrating humidity) is less likely to result in emissive leaks - and tends more to be contained within the component itself - than faults in the condenser, which almost always result in abrupt emergence of refrigerant. 13 This bears out the assumption that component defects falling within the low-loss category are different by nature from defects that lead to high or even total loss.



### 2. Air-conditioning system as obstacle to engine or radiator repairs

About 22% of all recoveries from an air-conditioning system that had not yet lost 40% of its refrigerant were performed not because of the system itself, but because it left other components inaccessible. In 17% of these cases, the air-conditioning system was in the way when dismantling and re-installing the engine, while on 5% of occasions, it created a problem when dismantling and fitting the radiator. Condensers and high-pressure lines were the main items requiring temporary removal. In such instances, an air-conditioning system is not actually opened because it is losing refrigerant, even if such loss may well be found in the process and duly rectified.



### 3. Establishment of accident damage and preparation for bodywork repairs

About 24% of recoveries in which less than 40% refrigerant was found to have been lost were performed on vehicles that had been in an accident.

Just as there are 'emissive' and 'non-emissive' compo nent defects, accidents can also be 'emissive' or

'non-emissive. 14 Accidents affecting the front of a vehicl e can damage the air-conditioning system severely, this being the main cause of 'total' loss of refrigerant. However, even an accident involving serious damage to panelling can also leave the air- conditioning system undamaged, or simply buckle its more exposed components.

Accordingly, there are two reasons for recovery from an accident vehicle. Firstly, the process serves to locate possible damage (loss of refrigerant) to the air-conditioning system, and secondly, the refrigerant must in any case be removed from the system befor e the vehicle is handed over to the body shop. An air-conditioning system cannot be welded or soldered when full, nor can welding or soldering work be done on the vehicle - or oven-drying after repairs to paintwork - because of the ri sk that portions of the system might heat up, the heat then producing excess pressure that could destroy its components. Furthermore, the refrigerant might produce decompos ition products which are not only toxic, but can also corrode piping and other parts of the system. The principal culprit here would be hydrogen fluoride (HF).

13 The condenser may suffer a 'non-emissive' defect when it is merely bent or dented in the course of a minor collision, without actually developing a leak. This component may also have to be replaced where heat exchange is inhibited by severe soiling, if t he mechanic is concerned that steam-jet cleaning might damage its fine blades.

14 Fischer (1997) had already distinguished between accidents destroying the air-conditioning system, and those leaving it undamaged.23



### 4. Leak tests at customer's or workshop's initiative

The level of refrigerant in a system had only been measured as a 'side-effect' in all of the recoveries mentioned so far, whereas recovery in about 30% of cases was directly aimed at (preventive) measurement of the refrigerant level.

Two thirds of these 'direct measurements' were carr ied out at the request or on the complaint of the customer, the principal motive being dissatisfaction with the cooling effect ("not cooling properly"). 15 The interesting point is that these measurements reve aled only about 10 to 15% loss of refrigerant on average, with just a few exceptional figures of up to 30%. In other words, it is unlikely that cooling capacity would have noticeably improved after rechar ging. I suspect, myself, that customers complain so often about deficient working of intact air-condit ioning systems because they expect far more of these systems than they can actually provide.

One third of these measurements were made at the in itiative of the mechanic, often because of the (unconfirmed) suspicion that a system fault whose cause was not otherwise to be found could in fact be due to lack of refrigerant.



### III. Consequences for Method of Esti mating the Rate of Emission

Even leaving out the 'middle' group of refrigerant losses between 40 and 99% (where specific reasons for opening the air-conditioning system overlap and are more difficult to distinguish), our analysis of system openings in connection with total loss a nd losses of less than 40% provide an important foundation for the principal goal of this study, namely the estimate of the annual rate of emission from passenger-car air-conditioning systems based on empirical findings.

The two results of our ideally typical 16 comparison of air-conditioning-system openings are

firstly: high ('total' in this instance) loss of refrigerant is attributable to 'irregular' defects in the refrigerant

circuit. The resultant leak causes the air-conditioni ng system to fail. The system has to be opened, this being arranged and done right away in the direct aim of remedying the source of loss; and

secondly: limited loss (assumed as up to 40% of the stan dard charge) does not in itself cause failure of the air-conditioning system. Loss of this kind is merely detected indirectly , when opening a system for

reasons other than remedying the source of loss - for instance the replacement of internally defective components, provision of access to the engine, emptying the system for work on the body, and preventive checking of the charge level.

In connection with the first of these two results we found that in principle, workshop records - provided they have been kept continuously for one year - document all instances of repa irs to irregular leaks. Accordingly, they cover the sum of 'irregular' emis sions produced by all of the air-conditioned vehicles

15 One exception would be t he vehicle owner wanting to know if his air-conditioni ng system was still refrigerant-tight after rubber components had been ni bbled by martens (incidentally, the system had not lost a single gram of refrigerant). Another was the driver wishing to be reassured of a full system before holidaying in a southern climate - an unusual case.

16 It should be clearly borne in mind that this comparison is 'ideally typical' because in reality, there is no sharp, distinguishing line to separate 'high' loss from 'low'. 'Total' loss may also be due to a 'regular' and not very emissive defect persisting over a sufficiently long period of time. Likewise, refrigerant loss less than 40% may be attributable to 'irregular', emissive damage which simply did not have sufficient time to permit any higher emergence of refrigerant.24

serviced by the workshop in question. An annual rate of irregular emission can therefore be determined from these records (see Chapter E).

The second result shows us that refrigerant loss of less than 40% is not generally attributable to 'irregular' damage, but, in principle, to regular le akage consequent on the design and mode of operation of mobile air-conditioning systems. Si nce these losses do not interfere wi th the system's operation, they are not usually measured directly. Some, however, are measured indirectly in the process of recovery, representing an unintentional but thoroughly usable random sample of 'normal' emission. An annual rate of regular emission can be determined from these measurements (see Chapter D).

Together, the annual rates of 'irregular' and 'regular' emission go to form the total annual rate of

emission.25



## D. The Annual Rate of Normal Emission

I. Regular Loss of Refrigerant from Intact Air-Conditioning Systems

'Regular' refrigerant loss does not mean that emissi on will take an identical course in every single airconditioning system. For instance, the period of ti me for which individual systems remain switched on scatters widely about a mean of 150 hours per annum (T axis-Reischl 2000). Then the life of a vehicle's engine (as it undergoes vibration and the development of heat), actually a more important aspect in the context of normal leakage, also varies widely about an average of 450 hours (in the same year, 1997) - and this is not allowing for mileage or for traffic cond itions. Another factor woul d be the driver's personal style at the wheel, which will have a varyingly stressful effect. Again, the way the air-conditioning system is handled and used has a part to play 17 , and the ambient temperature co-determining a system's pressure is not the same for every system (car ga raged or parked in the open). Moreover, the quality of workmanship in one air-conditioning system is ve ry rarely quite the same as in the next.

As starting point for the statistical analysis prov ided below, it has been taken that, while 'regularly' emitting car air-conditioning systems - originally charged ex-works with refrigerant R-134a (from 1993 on) - may have lost varying quantities of refrigerant up to the measurement period 'mid 1999 to mid 2001', as a general rule they still contain enough to permit normal operation - provided they are free of any 'irregular' defect.

In a first approximation, air-conditi oning systems found to have lost less than 40% refrigerant were duly selected from the study population and deemed to be 'normally' or 'regularly' emitting systems, because to go by the experience of interview ed air-conditioning mechanics, 60% of the original refrigerant charge is the mean limit at which a system is still marginally intact - see Chapter C, Section II.

Bearing in mind its technical imprecision, the '40% Mark' should be applied with a margin of error extending above and below, as necessary statistical aid fo r want of more suitable criteria governing the quantity of refrigerant deemed "sufficient" or "no lon ger sufficient" for a system's continued operation. Another factor to be taken into account is the gener al imprecision, discussed in Chapter B, in the measurement of recovery volumes (deviation by up to 50 grams is usual) and therefore inherent in all empirically determined rates of loss. The present st udy deals only with general orders of magnitude, not with absolutely exact quantities.

The average refrigerant charge in air-conditioning systems having losses of less than 40% is 825 grams, consequently being somewhat lower than in all 678 fully identified vehicles (where the average is 848 grams). See Chapter A. 7. The charge for Brand 1 is 738 grams, for Brand 2 it is 831 grams, and for Brand 3, 898 grams.



### II. All 282 Emission Rates of < 40 % as a Function of Vehicle Age

Plotting the rate of loss recorded (as differenc e between recovered quantity and standard ex-works charge) at the time of opening all air-conditioni ng systems whose age could be determined and which had lost < 40% refrigerant (282 units) against the peri od elapsing since the vehicle's first registration, the scatter diagram (Diagram 2) shows hardly any relation between the two quantities.

17 Only a minority of drivers occasi onally run their air-conditioning system for brief periods during the cold part of the year. This is an important way of ca ring for hoses and seals, allowing oil and refrigerant to pass through them and protect them from drying out, becoming brittle, and therefore ageing more rapidly.26



### E m issio n R a te in M o n t h s sin ce F i r s t R e g i str a tio n - all

282S y s tem s lo sin g < 40% R e fr ig er an t (u n c o r r ected )

4 0 % Line

0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6 1 0 8



### m onths s i nc e fi rs t re gi s t ra ti onER < 40 % E R < 40%

Diagram 2: Emissi on rates (rate s of loss) of all 282 sy stem s losin g < 40% ref r ige r ant (u ncorre cted) in

months sin c e first regi strati on. The data points of the 282 individu al emissi on rates are broadl y scattered

belo w the 40 % Line witho u t taking any clea r directio n. The only si gnifica nt factor is thei r anti c ipate d

accumul a tion on the left of the x-axis, wo rksho p visits being con c e n t rated on the first 48 month s duly covered by warranty or goodwill pr ovisi ons. ER = em issi on rate.

Diag ram 2 re veals a diffusely scatte red point clo ud b e lo w the 4 0 % Line. The onl y significa nt factor i s the expecte d accumulation to the left of the x-axis, 82% o f workshop visits bei ng con c entrated wit h in the first 48 months, whi c h are still covered bywarranty or good will arrangement s.

There is still no clear trend to be disc erned on calculating t h e a v e r a g e f i g u r e p e r year (me an value for

months 0 to 1 2 , 13 to 24, etc.) of the wid e ly scatte red individual lo ss rate s

The ann ual a v erage s do g enerally conti nue to rise up as far a s the seventh yea r , from 13% to 24%, but then they fall back ag ain to the initial figure in the follo wing two years - see Dia g ram 3.

The 'an nual a v erage s' curv e makin g its way throu gh the point cl ou d of 282 "mo n thly emissi o n rate"

combi nation s fails to revea l any depen d ence of emission rate on vehicl e age.27



### A

v er ag e L o ss F i g u r es in in d i v i d u al Y ear s o f L i fe o f all 282 A i r
C o n d itio n i n g S y stem s lo sin g < 40% R e fr ig er an t (u n c o r r ected )

0 10 20 30 40

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6



### m o n t h s sin ce v e h i cle fir s t r e g i ster edpercentile loss

Diag ram 3: Trend by month of emissio n rates un der 4 0 % (uncorre cted). The p a th of the curve l eadin g throug h the p o int clou d of Diag ram 2 ( q.v .) reve als n o t hing sp ecifi c to indicate a depe nden ce of

emission rate on vehicle a ge. The ri se o b se rved up to the seventh year (b etwe e n months 5 4 and 66 ) stop s, and th en the cu rve drop s ba ck d o wn a gain.

Diag ram s 2 a nd 3 demo n st rate that whil e con c e n trati on on air-con ditioning syst ems lo sing le ss tha n 40% refrig era n t may be a neces sar y or unav o idable means of ide n tifying exclu s ively 'reg ular' or

'norm a l' emi s sion , it is not in itself sufficient . The source s of emi ssi on in ou r 2 82 air-conditi oning system s lo sin g less than 4 0 % refrige r a n t are clea rly n o t all of a 'reg ular' n a ture, so the next stage in the study wa s to make a co rre ction, attempt i ng to elimina t e system s wi th 'irreg u la r' refrige r ant lo sse s from the total figure.



### III. Stat istical Correction of Normal Emiss i on Rates

Of the 282 air-co nditioni ng system s lo sin g less t han 4 0 % refrige r a n t, 216 (77%) still remai ned after

statistical co rrection aim ed at rest ri cting t he numb e r of cases to ge n u inely 're gula r ' emi ssio n s. For me,

this sel e ctio n rep r e s ent s ou r unintentio na lly made ra n d o m sam p ling of car ai r-con d itioning syst ems (a)

sufficie n tly ch arge d with refrige r ant an d (b) sol e ly pro d u cin g 'no rmal' emissi on. Se ven of the 66

elimination s were ba sed o n the explana tion given in the Re co rd Sh eet, and then there were 59

anomali e s eit her ab ove or belo w the line

.



### 1. Recognisable as 'irregular' from the Record Sheets: seven cases

In three of these ca se s, the mech ani cs' notes in the Re cord Sheet s made it po ssible to categ o rise refrig era n t loss < 40% a s 'irregul ar'. T w ice the not es e x pressly indi cated lea ks in the comp re ssor, and once they recorde d an a cci dent as cau s e of 20% emi ssi on (a yea r and half after first regi stration). In a

further fou r case s, the Re cord She e ts in dicate p r ev io us lo sses in p r ecedin g years, whi c h, wh e n adde d28

to the loss in the curre n t year (2 000, 20 0 1 ), pro d u c e more tha n 40 % leakag e of refrig era n t an d can

therefo r e be t a ke n out of the equatio n.



### 2. Eliminating anomalies above and belo w th e line: 59 c ases

Most of the 'irregul ar' ca se s of emission were identifie d as an omalo u s pe aks or trough s when we applie d a pla u sibl e crite r io n.



### R estr i ctio n to 216 C ases o f 'R eg u l ar ' E m issio n < 40%
(S tatistical C o r r ectio n )

0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6 1 0 8



### m o n t h s sin ce v e h i cle fir s t r e g i ster edpercentile emission rate

E R < 40%

boundar y

Diag ram 4: Restri ction to 2 16 ca se s of 'regula r ' emi ssi on < 40%. Th e diagram sh ows the sam e 282

ca se s of emission a s in Di a g ram 2, but, followin g st ati s tical corre c ti on, 66 of them are no w ou tside the

boun dary (ou t side left and bottom right) and 21 6 are l e ft inside. Basically, cases of emissio n are

con d itionally eliminated a s 'irreg u la r' wh ere they ar e either fou r times hig her o r four time s lower (mea su rem e nts of that ord e r first o c cu rri ng after 42 m onths) than th e averag e.

Losse s amo u n t i n g t o f o u r t i m e s the ave r age (b efore correctio n ) a r e classified h e r e a s a b norma l peaks

. This fa ctor is not based on any gene ral statistical rul e - indee d, in the final analysi s , it is some what arbitrary. Importantly for m e , though, I feel it is hi gh en ough to preve n t any emissi ons that migh t in fact

be 'no rmal' from being rule d out as bei n g 'irre gula r '. T o my mind, emissi on s of over four time s the

averag e wo ul d seem to be so excessive that they ar e highly likely to have their source in an 'i rregul ar'

defect. 18

The average l o ss per m ont h is 0.55% - whi c h is 5.5% after ten months. Co nstell ations li ke "1 0 months /

22% loss" ca n therefo r e b e eliminated (22% being 4 x 5.5%). 38 case s met this criteri on for a nomalo u s

18 Redu cin g the factor 4 to 3 for anomali e s above the li ne and, corre s po ndin g ly, from 1⁄4 to 1/3 for those

belo w wo uld only just abo ut exclude n o more than si x further ca se s (three up a nd three d o wn), so I did

not think there wa s any pa rticula r be nefi t to be gained from this kin d of prelimin a r y rest riction of the

rang e of emission s.29

pea ks. 33 in d i cated lo sse s of over four times the av e r age in the first year, six more re aching th is level

after at most 17 month s . By definition, anomalo u s p e a ks are to be found only du ring the first 18 months of vehicle ag e, the 40% emissi on limit being ex cee d ed after 19 m onths a nd air-con ditioning systems above that limit no longe r being ta ken i n to con s id era t ion.

Emissi on s a m ounting to n o more tha n a q u a r t e r of the avera ge rate of loss (b efore corre c tion) were

deeme d to be a n o m a l o u s trough s . Such l o w emi ssi on s as these are rega rd ed a s unre a listi c, si nce it

woul d have to be assum e d that air- con d itioning syst ems falling u nder that he a d ing would h a ve suffere d

some p r evio u s loss. Ho we ver, this crite r ion only appli e s to emi ssio n s from vehi cles old e r than 3.5 years

or 42 mo nths. All lower lo sses up to that time are rega rded a s 're gul ar', incl udin g the nume r o u s 'ze r o'

emission s.



### A v er ag e R e fr ig er an t L o ss in in d i v i d u al Y e ar s o f L i fe o f 216 A i r
C o n d itio n i n g S y stem s lo sin g < 40% R e fr ig er an t - after

C o r r ectio n

0 10 20 30 40

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4



### mo nt hs s i nc e f i rs t re g i s t ra t i o npercentile loss

Diag ram 5: Average refrig erant lo ss in i ndividual yea r s of life of 21 6 air-co ndi tio n ing sy stems losin g < 40% refrig era n t, after corre c tion. The curve now sh o w s a cle a rly ri si ng trend, pa ssing fro m abo ut 4% (the mea n for the first 12 months) to just unde r 29% (t he mean fo r months 6 0 to 72), even if the rise i s briefly interru p ted between the 48 th and 60 th month. O u r co rrectio n leaves u s with no meanin g ful

averag e for the peri od afte r seven yea r s, becau se the r e is only on e instan ce of loss left in that period. Comp ared wi th Diagram 3 (un c o rre cted trend ), the sc attered an nu al averag es f o r the 'corre cted' ca se s now follo w a distin ct prin ci pal dire ction going fro m bo ttom left to top right. The curve is neith e r moved up by overly high emission ra tes to the left, nor forced d o wn by un derstated rates t o the right.

After 42 mont hs, ze ro lo sses are in the first pla c e unli k ely, and in the se co nd pl ace, 42 mo nths was the maximum pe riod for whi c h I had an unb roke n re co rd o f the opening of air-con d itio ning sy stems. The eliminating cri t erion 'le s s than a qua rter t he avera ge lo ss of 0.55% p e r month' first began to take effect

in the 43rd m onth, duly ide n tifying 20 an omalou s tr o u ghs (14 zero losse s and 5 l o sse s of less than 10%). Only o ne of these case s exceed ed 10% (a ctu a lly 12%), bei ng found afte r 106 mo nths. That ca se

wa s eliminate d like the oth e rs b e cau s e, althoug h not h i ng ca n be proven in the a b se nce of rel e vant data, it is highly likely to be associate d with a previou s loss.30

The co rrecte d ca se s of emissi on a r e to be found in si de the b oun dary in Dia g ram 4. The location of the

anomali e s a b o ve and bel o w the line is g r aphi cally obv ious , the excessive emissi ons of the first year and a half being l e ft outside to the left, and the understated emissions after the firs t three and a half years

appe arin g at bottom right. Diag ram 5 sh ows at first gl ance that, wh ere combi ned to produ ce a nnual

averag es, the emissi on rates left after el iminati ng the 59 anom alie s (and the oth e r seve n 'irre gular'

ca se s) follo w a definite up ward tren d in pace with the life of the ve hicle - u n like the situatio n in Diag ram 3. It is my opinion that the corre c ted ca ses furni s h sui t able found ation materi al for the attempt made in Section IV to arrive at a qu antitative determi n a tion of the annu al rat e of normal e m issi on.



### IV. The corrected 6.3% Annu al Rate of Normal Emission

The ann ual rate of normal emission i s calcul ated fr o m the 0.523 % monthly averag e of all 216 co rrecte d

emission rate s duri ng the p e riod 0 to 85 months, bei n g twelve times the monthly average, viz. 6.3 %

. Specifically, this rate of em issi on applies solely to air-con d itioning systems in veh i cle s up to se ven years old, and is su bject to so me degre e of un certai nty on ac count of the rathe r arbit r ary choice of co rre ction

factor. The ra te comp rises the emission of all thr ee ca r bra n d s take n together, di stinctio ns b e twee n them being e x amined in S e ction V belo w

.



### C o rre c t e d A nnua l R a t e o f N o rma l Emi s s i o n f o r A i r- C o nd i t i o ni ng
S y stem s u p to S e v e n Y ear s o l d (216 C ase s lo sin g < 40%

R e fr ig er an t)

4 0 % Line



### 0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6



### mo nt hs s i nc e f i rs t re g i s t ra t i o npercentile rate of emission

E R < 40%

averag e

Diag ram 6: T he ann ual rat e of normal e m issi on from all 216 sy ste m s losi ng < 4 0 % refrige r a n t (co r recte d ). T he amou nt by which these norm a l em issions in crea se each yea r is the 'annu al a v erage refrig era n t loss' from all correcte d ca se s, so it appea rs as a straight line in the gra ph. The rate i s 6.3%. The straight-li ne avera ge e x tends from i n tersectio n -p oint zero to interse c t with t he 40% Line after 76

months. In cid entally, beca u se of this 4 0 % barrie r , dat a points after the 76 th month are al ways belo w the straig ht-lin e a v erage, neve r above it, wh ich lo wers the average m a thematically.31

Plotting the monthly 0.52% or ann ual 6.3 % along the x-ax is (m onth s since first re gistratio n of vehicl e), a straig ht line is produ ce d wh ich interse c ts the 40% Mark (still just en ough refrig erant) after 76 months (76.4 ) , i.e. after six years a nd five months.

Since the 6.3 % figure is an average cal c ulated from widely scattere d individual case s, duly

comp en satin g for major va riation s up wa rds a nd do wn wards, it woul d not of cou r se be true to say that in

pra c tice, all car air-conditio n ing sy stems will com e to a stand still after 76 month s . Drive r s' exp e rience

woul d indicate to the contrary, one havi ng visited the workshop a s often as two times in seve n years o n

accou n t of his air-conditio n ing sy stem, anothe r neve r hav ing be en there at all. (A third driver had hi s aircon d itioning system ch arg e d else wh ere, this ca se n o t being exami n ed any furthe r in our study).

Ho wever, the figure doe s mean that - le aving asi de a n y of the other empiri cal in accuraci es of the

pre s ent stu d y - on avera g e 6.3% of the origin al refri g erant cha r ge i s lost by othe r than 'irreg ul ar' mea n s whe n we ta ke the first seve n years a s ou r base line.



### V. Differences in Normal Emission betw een the Three Car Brands

The followi ng three diag ra ms (7 to 9 ) sh ow the no rma l annual emi s sion rates fo r each of the study's

three b r an ds of car. It shou ld be emph asised that the ca se s are n o t suf f i cient in number to let us draw any dire ct co nclu sio n s fro m them (or from their average) with re g a rd to the situ ation in realit y. However,

the indicated differen c e s are none the le ss imp o rta n t for all that, allowin g us a s they do to see how the

annu al rate s of normal emi ssi on ra nge u p wa rd s and d o wn wa rd s.



### A nnua l R a t e o f N o rma l Emi s s i o n a n d C o r r e c t e d C ases o f

E m issio n am o n g th e 77 V e h i cles o f B r an d 1

0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6



### mo nt hs s i nc e f i rs t re g i s t ra t i o npercentile rate of emission

E R < 40%

averag e

Diag ram 7: Annual rate of norm a l emission and corre c ted cases of emissi on am ong the 77 ve hicle s of

Brand 1. Con d itions for Brand 1 are alm o st the sa me as in the overall sele ction - monthly rate: 0.52%;

annu al rate: 6

. 2%; 40% Line intersecte d after 77.3 mo nths.32

Diag ram 8: Annual rate of norm a l emission and corre c ted cases of emissi on am ong the 60 ve hicle s of

Brand 2. Bra nd 2 indi cate s the high est emission ra te s - 0.59% pe r month and 7. 0% per year. The 40%

Line is inte rsected by a s e a rly as 68.2 months.



### A n n u a l Rat e o f No r m al Emi s si on an d Co r r e c t e d Cas es o f

Emi ssi o n amo n g t h e 7 9 V e h i cl es o f Br an d 3

0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6



### m o nths s i nc e fi r s t r e g i s t r a tio npercentile rate ofemission

ER < 4 0

aver ag e 

### A nnua l R a te o f N o r m a l E m is s i o n a n d C o rr e c t e d C ases o f

E m i ssi o n amo n g t h e 60 V e h i cl es o f Br an d 2

0 10 20 30 40 50

0 1 2 2 4 3 6 4 8 6 0 7 2 8 4 9 6



### mo n t h s si n ce f i r s t r e g i st r a t i o npercentile rate of emission

ER < 4 0

aver ag e

Diag ram 9: Annual rate of norm a l emission and corre c ted cases of emissi on am ong the 79 ve hicle s of

Brand 3. Bra nd 3 ha s the lowe st emissi on rate s of the whol e pop u l ation, bei ng j u st 0.49% pe r month and 5.8% pe r year. The 40 % Line is inte rse c ted by a s late as 82.1 months.

The ann ual n o rmal rates of emissi on differ by more th an 1% (ra ngi ng from 5.8 to 7.0) betwee n the three

bran ds of car. The 40% Lin e is interse c ted after 68 m onths by Bra nd 2, but not until after 82 by Brand 3.33



### VI. Car Manufacturer Specifications concerning Normal Leakage

Placed in rela tion to the averag e 825 g r am cha r g e of air-co nditioni ng syste m s lo sing le ss than 40% refrig era n t (see introd uctio n to the pre s e n t Chapte r D), the annual a v erage of 6.3 % repre s e n t s a n o r m a l (not total) refrigera n t leaka g e l e v e l o f 5 2 gram s per ye ar

.

Fig. 3: Car ai r-co nditioni ng system sho w i ng the prin cip a l points of R-134 a eme r g ence und er th e

con d ition s of norm a l refri g erant lea k a g e stipulated by the car ma nu facture r s. An annu al leaka ge of at

most 10 to 30 gram s is ad missi ble from the shaft sea l of the compressor (4 excl amation ma rks), altogethe r 10 to 20 gram s (two exclam ation marks ea ch) from the h o se system (t he illustration sho w s four hoses), and 2 to 3 grams from each O ring (there are eleven such seali ng ri ngs in the illustration). Adding up th e figure s , ann ual losse s of from 42 to 83 gram s are co nsid ere d " normal" in the system

illustrated. The number of exclamation marks (! ) stand for the relati ve importance of the particular

sou r ce of lea k ag e. Refrig e r ant ci rcuit: 1 = evapo rato r; 2 = com p re ssor; 3 = co nd enser; 4 =

colle ctor/d rye r ; 5 = expan si on valve.

Source: WAE C O (m odified ).

Acco rdi ng to the su pplie rs of complete car air-c onditio n ing sy stems (Air-Co ndition ing Co nfere n ce - 2001 ), ca r manufa c ture rs spe c ify margi n s - for the le aka ge of refri gera n t throu g h seal s an d h o se s - within which a car ai r-conditi oning sy stem will be accepted as "r efrigerant-tight". Under these

spe c ification s , the annual l o ss of refrig erant must be kept within the following b o u nds:34

• compressor shaft-seal: 10 to 30 grams, • flexible hose lines: 10 to 20 grams, and • each O ring at connections to components: 2 to 3 grams.

The number of connections to the components 'compr essor', 'evaporator', 'c ondenser', 'dryer' and 'expansion' valve' (all of which can be dismantled), and therefore the number of O-ring seals, varies from seven to eleven according to system design. Accordingly, normal leakage through the O rings is allowed to vary between 14 and 33 grams. 19

The annual loss of refrigerant accepted by the ca r manufacturers amounts to between 34 and 83 grams when all three sources are added together.

The average 52 grams the present study has defined as normal emission per year per air-conditioning system over a period of seven years in use comes about midway in relation to the manufacturers' overall allowance. Far from contradicting the car makers' sti pulations, the study figure confirms how closely they approach reality.

Looking at matters in reverse, the allowances confirm how close to reality is the result arrived at from the selected workshops' Record Sheets, ranging as it does from 46 grams (Brand 1) to 58 grams (Brand 2) among the three car brands. The normal annual loss recorded for Brand 3 coincides with the average loss figure of 52 grams.

19 Integration of the dryer with the condenser, an approach already to be found at the present time, saves on two connections and therefore on sources of loss amounting to about 5 grams. The same can be said of integrating the expansion valve with the evaporator. Then the widely introduced reduction in the proportion of elastomer connection lines between components in favour of aluminium piping has also reduced normal leakage. However, there are limit s to the replacement of hoses with pipes, in part because of the better heat and sound insulation provided by flexible elastomer lines. In fact, the single line most severely exposed to high pressure (up to 20 bar) and high temperature (the gas being "superheated" to above 100 °C), the pressure line from compressor to condenser, lends itself least to being replaced with a metal tube, because not only does it need to be very large in diameter and highly flexible, it must also be capable of compensating for the vibrations of the engine to which it is connected.35



## E. The Annual Rate of 'Irregular' Emission

The approach I took when determining the 'normal' rate of emission was an indirect one. The data obtained on refrigerant recoveries from car air- conditioning systems losing less than 40% served as a "workshop sample" of vehicles which, for the most part, had not in fact visited the workshop primarily because of a problem with their air-conditioning sy stem. The situation is otherwise for 'irregular' emission, which makes itself felt in the form of obv iously faulty behaviour or functional failure, readily noticeable to the driver when switching on. A visit to the workshop inevitably follows, even if after some delay which may indeed extend to several months in the colder part of the year (see diagram in Chapter A).

It has been taken as a starting point for the following se ries of estimates that, on principle, 'irregular' cases of emission (whose treatment necessarily calls for an opening - recovery and recharging - of the air-conditioning system) are dealt with by the origi nally designated workshop, which, where Record Sheets are kept, will also document the process. The 'non-normal' em issions contained in the Record Sheets (namely all refrigerant losses of over 40%, and those under 40% that were eliminated by the correction described in Chapter D) therefore directly represent the entirety of 'irregular' emissions from - basically - all vehicles making up the regular 'client fleet' of a particular workshop.



### I. Inspections as Reference Quantity for Cases of Irregular Emission

In terms of volume, the 'regular client fleet' is unde rstood to mean all the vehicles that would be brought to a particular workshop in the event of a fault in their air-conditioning system; in other words, all the vehicles belonging to regular customers - who are also referred to as "loyal" customers in the jargon of the motor industry. The question now arises of finding a suitable company 'figur e' to account for these customers. A garage's registered daily throughput of vehicles would be too high, because it would include multiple countings of one and the same vehicle. The 'annual inspections' figure, of which garages also keep an account, would seem to be the most appropriate. Regular inspections include "major" and "minor" versions, which may also be refe rred to as 'maintenance' or 'after-care' services depending on the make of vehicle. C onveniently for our present purposes, on average every vehicle in Germany underwent approximately one (1.05) regular maintenance/inspection service in the year 2000 (DAT-Veedol 2001, 23 et seq.). In other words, we can take it that the number of annual inspections equals the number of vehicles constituting a garage's annual 'regular client fleet'.

All nine garages in our selected population provid ed us with figures on their number of vehicle throughputs and number of regular annual inspections during at least one whole year in which refrigerant records had been kept (years 1999 or 2000, or the twelve-month period May 2000 to May 2001) - see Table 4.

Table 4: Annual Vehicle Throughputs and Inspections by Brand of Car and "Irregular" Emissions from 1999 to 2001 in Nine Garages 1. Throughput 2. Inspections 2. as %

of 1. 4. Irregular Emissions 4. as %

of 2

Brand 1 30,396 8,495 28% 113 1.3%

Brand 2 57,226 16,118 28% 200 1.2%

Brand 3 37,966 9,556 25% 167 1.7%

Total 125,588 34,169 27% 480 1.4% Source: reports and refrigerant records from nine garages from 1999 to 2001.

As Table 4 indicates, 34,169 or 27% of 125,588 vehicle throughputs constituted 'regular annual inspections'. These 34,169 vehicles represent the per manent 'client fleet' of vehicles serviced by the36

study's nine 'authorised dealers'. Out of this 'client fleet', 480 air-conditioning systems producing 'irregular' emissions were opened during the period of one year, representing an average 1.4% of all three brands of car, all of whose individual perce ntages are in any case very alike. (Adding the 175 systems opened in connection with 'normal' emissi on, 655 systems were duly emptied and recharged, representing 1.9% of "regular customer cars".)

The cases of emission used in this chapter (480 in number) have been chosen as a function of whether or not the date of their detection (and entry in the re cords) falls within an 'inspection year' (reference period) at my disposal. For instance, where the 'inspection year' is the year 2000, I have eliminated emissions subsequent to January 2001 that I did in fact use in another connection - in the previous chapter for example. This confinement is in fact matched by a corresponding broadening of our scope: since our sole interest at this point is in the level of an emission and in the brand of vehicle producing same, we can also take account of cases in wh ich the age of the vehicle or even its type proved impossible to determine.

The garages did often raise an obvious objection to t he idea of using 'inspections' as a basis for our study of air-conditioning systems, claiming that the air-conditioning system does not belong to the

normal work of routine maintenance and that most f aults are actually reported by the customer himself, outside the ambit of an 'inspection'. This objection is not really relevant to our present purposes, since the 'inspections' serve solely as quantitative refe rence point for recorded emissions of refrigerant, concentrating in fact on their upper limit.



### II. Confinement of Inspections to Vehicles with Air-Conditioning System

It should go without saying that refrigerant emission would not be examined in relation to all inspected vehicles, but just to those of them duly equipped with an air-conditioning system.

Several intermediate steps were required in the proces s of confining the registered 'inspections' to those conducted on air-conditioned vehicles (and specific ally those with an original R-134a system), none of the garages having classified their inspections underthe headings of vehicles with and without airconditioning system.

Every year since 1993, the percentage of new cars equipped with air-conditioning system has been growing at a very substantial rate, and the point of saturation is not yet in sight. Consequently, the percentage of vehicles equipped with air-conditioning is different not only for each brand of car, but also for each 'year of registration' of each car, quite apart from further differences existing between the numerous types of a particular brand.

The two main steps to be taken in determining a brand-tied garage's quota of air-conditioning systems in a given 'inspection year' (the year 2000, for instance) are

• firstly , arrangement of the garage's total number of vehicle inspections into their individual 'years of registration' (obtaining the 'age pattern'), and

• secondly , determination of the specific quota of air-co nditioning systems (MAC Quota) in each of a particular car brand's 'years of registration'.

The MAC quota for an 'inspection year' is first arrived at by relating t he MAC Quotas of specific years to the proportion (in terms of quantity) of cars from those years that call to a garage in the current 'inspection year'. In making this calculation, we do have to take on board a measurement error attributable to the fact that MAC Quotas for specif ic years are only obtainable for Germany as a whole,37

so they may differ to a gre a ter or le sser degree from t he 'quota s ' of the vehicle s servi c ed by a particul a r

gara ge.



### 1. Model of Age Patterns in Annual Inspections

What inte rest s a garage m o st in re spe c t of a 'year of registration' i s the percenta g e of vehicle s from that year that actu ally come into the garag e for insp e c tion (thereby dem onstrating loy a lty to the company). Apart from ga rage re cords, there is al so a more g ene ral body of data available o n these visit s , as well

as on the d e clining tende n c y to avail of an 'autho ri se d deale r ' workshop a s a vehicl e be com e s old e r - for

instan ce, the DAT-Ve edol 2001 survey. The num ber of annual in spectio n s cate gori s ed by ag e of vehicle

is anoth e r qu estion, on e n o t normally in vestigated by the garag es even thoug h asso ciated wi th their first

interes t.

Wo rkin g toge ther with a nu mber of servi c e man age rs and the re gio nal sal e s d e p a rtment of on e Germ an manufa c turer, we develop ed a model of the age patte rn eme r gin g in annu al insp ection s, whi c h, at least for the year 2 000, pro bably come s very clo s e to the reality of the situation in aut hori s ed -d eale r worksho p s. T h is is b e cau s e expert esti mations fo r the year 200 0 were su ppo rt ed, in three of the

gara g e s (cov ering two ca r bran ds), by the comp any compute r whi c h ran a p r og ram sele cting i n sp ecte d

vehicle s by the year of their first regi stra ti on. Our mo de l is rep r od uce d in Diag ram 10.



### A n n u a l I n spe c ti on s c o m p i l e d by A g e of V e h i cl eM odel for 2 0 0 0 - G e r m an A u th or i s e d D e al er W o r k sh ops / O u tl e t s

20 %

18 %

16 %

14 %

8%
7%
5%
4% 10 %



### 0% 5% 10 % 15 % 20 % 25 %

123 4 5 6 7 8 8 t o 1 5

et s e q

. 

### y ear s sin c e fir s t r e g i s t r a tio nPercentile share of allinspections in year


### al l i n s p e c t i o n s = 10 0 %

Diag ram 1 0 : Annual in spe c tion s com p il ed by age of vehicle. Mod e l for 2000, a u thori s ed d e a l er worksho p s/o u tlets. More t han two third s of all insp ec tions are co n c entrated wit h in the first fe w years of a

vehicle' s ag e, older vehi cle s acco unti ng for less than a third of the total.38

The diagram clearly shows the preponderance of inspections in the earliest years (68% in total), which is hardly surprising given the four-year loyalt y-maintaining attraction of warranty and goodwill arrangements. Vehicles more than four years old (t he time when changes of ownership begin to occur) together make up only one third of the inspections tota l. The two bars on the far right of the diagram deserve particular attention - in the year 2000, 14% of inspected vehicles were eight and more years old, meaning that this 14% of vehicles are very likely not to have been fitted ex-works with an R-134a air-conditioning system, which first really came into general use in 1993 or 1994.

The 'age pattern model' is based on the inspections carried out in all three of the reference periods in question, namely years 1999 and 2000, and the twelve months from May 2000 to May 2001.



### 2. Air-conditioning quotas in inspection periods 1999, 2000 and 2001

All six German mass-producers of passenger cars reported the number of each of their passenger-cartypes (ranging from five by BMW and Audi, to fifteen by Ford) equipped ex-works with an airconditioning system and sold in Germany in 1999 and 2000. They also provided specific information on types during the complex changeover phase from R-12 to R-134a, that lasted from mid 1991 to the end of 1993. Drawing as well on the data held in ÖKO-Re cherche archives for the years 1994 to 1998, we then duly worked out the brand-specific quota of ai r-conditioning systems (the MAC Quota), in each calendar year, from the type-specific data in our possession.

Table 5: Percentage Air-Conditioned of New Cars sold in Germany (German brands only, from 1995 to 2000)

Brand 2000 1999 1998 1997 1996 1995

A 97% 93% 84% 84% 75% 71%

B 97% 93% 91% 81% 75% 57%

C 94% 90% 87% 75% 67% 58%

D 80% 74% 63% 46% 24% 20%

E 82% 78% 64% 55% 40% 19%

F 82% 75% 66% 55% 17% 11%

Table 5 reproduces these quotas without giving the names of the car brands, so that the identify of the three brands of car actually chosen for our stud y cannot be inferred from the brand-specific airconditioning quota for the inspection periods - whic h itself is based on the quotas of 1992 to 2000 et seq. (see below).

The final step was to weight the MAC Quota for each year with the percentile share each 'year of registration' enjoyed in the annual inspection total, as illustrated in Diagram 10.

A total of nine MAC Quotas were arrived at in this way, three for each of the three chosen car brands: one for Inspection Year 1999, one for 2000 and one for May 2000 to May 2001.

Table 6: Air-Conditioning Quotas (MAC Q uotas) in the three Inspection Periods 1999 to 2001 by Brand of Car

Period Brand 1 Brand 2 Brand 3 Inspections in 1999 64% 37% 68% Inspections in 2000 73% 47% 75% Inspections from 5/2000 to 5/2001 78% 53% 80%

As a result of the general increase in MAC Quotas over time, the MAC Quota for inspections in the period May 2000 to May 2001 is distinctly higher than that in the year 1999. These quotas are likely to continue growing for the foreseeable future.39

Brand 3's MAC Quota of 75% for "Inspections in 2000" (Table 6, last column, second last line) indicates that of the vehicles undergoing annual inspection in the year 2000, 75% were equipped ex-works with an R-134a air-conditioning system.



### 3. 'Workshop Rate' of air-conditioned vehicles

Eighteen times in total we were able to relate whole-year 'irregular' emissions from the three car brands to the respective 'inspection periods' in which they had been detected - four times for the full calendar year 1999, ten times for full calendar year 2000, and four times for the period May 2000 to May 2001. On summing up our individual calculations and arrang ing our figures by brand of car, we obtain the percentage of 'irregular' emissions encountered in workshop inspections of vehicles having an airconditioning system. I have called this percentage the 'Workshop Rate' (Table 7).

Table 7: The 'Workshop Rate' ('Irregular' Emissions) of Air-Conditioned Vehicles of the Three Brands in 1999 to 2001 (Nine Garages)

All inspections Average
MAC Quota Inspections of

MAC cars Irregular

emissions Workshop

Rate

Brand 1 8,495 73% 6,202 113 1.8%

Brand 2 16,118 48% 7,772 200 2.6%

Brand 3 9,556 77% 7,370 167 2.3%

Total 34,169 62% 21,344 480 2.2%

During the same period in which the nine garages detected and recorded 480 'irregular' cases of emission, they inspected a total of 21,344 air-conditi oned vehicles (not their air-conditioning systems!). The number of inspections of vehicles having an air-conditioning system ('MAC cars') has been calculated here through multiplying the total number of inspections by the MAC Quota for the specific brand. This MAC Quota adds up to an average of 62% fo r the three brands of car, being at its lowest for Brand 2 (48%) and its highest for Brand 3 (77%). The (mathematical) percentage of 'irregular' emissions found when inspecting 'MAC cars' - or the 'Workshop Rate of MAC Cars' - averages out at 2.2% for all

three brands.



### III. The Annual Rate of 'Irregular' Emission

The rate of 'irregular' emission is arrived at by weight ing the 'workshop rate of MAC cars' with the rate of refrigerant loss discovered on opening air-conditioning systems. These loss rates, obtained from the Record Sheets, were available as percentages and as absolute figures for all 480 vehicles in question, and are entered in Table 8 along with the resultant br and-specific annual rates of irregular emission.

Table 8: The Annual Rate of Irregular Emission from Air-Conditioning Systems of the three Brands of Car in 1999 to 2001 (Nine Garages) Irregular

emissions Workshop

Rate Refrigerant loss in kg Rate of

loss* Annual rate of irregular

emission

Brand 1 113 1.8% 67.0 82% 1.5%

Brand 2 200 2.6% 147.3 85% 2.2%

Brand 3 167 2.3% 133.1 84% 1.9%

Total 480 2.2% 347.4 84% 1.9% * percentile relationship of "refrigerant loss in kg " to the sum of standard ch arge quantities of 81.4 kg (Brand 1), 173 kg (Brand 2) and 158.5 kg (Brand 3), adding up to 412.9 kg.40

The annual rate of irregular emission is lower t han the 'workshop rate' (averaging 2.2%), being only

1.9% because of the loss-rate of less than 100%, namely 84%.

Among the three car brands, this annual rate varies from 1.5% (Brand 1) to 2.2% (Brand 3)., being about one third as high as the rate of 'norm al' emission (6.3% according to our study).

The measurement error referred to in Chapter B - "omi tted entry" of the recovery operation - is seen to produce only a very slight 'absolute' increase in t he emission rate. Assuming 5% forgotten entries and a correspondingly 5% higher irregular loss of refrigerant, the annual rate of irregular emission would rise from 1.9 to barely 2.0 %, in other wo rds, by just 0.1% in absolute terms.41



## F. The Annual Total Rate of Emission for Air-Conditioning Systems

at most Seven Years old

I. The Calculated 8.2% Rate of Emission

The average annual rate of emission is arrived at by adding the rate of 'normal' emission to the rate of 'irregular' emission.

The annual rate of normal emission is 6.3% on avera ge, while the annual rate of irregular emission is 1.9% on average, so the annual total rate of emission runs out at 8.2%

.

This means that passenger cars having an ex-works R-134a air-condi tioning system lose over eight percent of their refrigerant charge every year. Placed in relationship with t he average charge quantity of 856 g, that percentage represents 70 grams per annum. Which is not to say that all of the corresponding refrigerant is topped up again, this hitherto only being done for a portion of the airconditioning systems found to have irregular losses and defects. Most air-conditioned vehicles simply produce 'normal' emission and have not yet reached the critical charge-limit (around 60%) because they are still too young to have done so.

An important reservation should be mentioned at this point, to the effect that our emission rates apply only to vehicles in operation for at most sev en years from the date of their first registration . Older vehicles (more than 84 months) are not included in ourdetermination of the rate of normal emission. R134a air-conditioning systems have only been on the mark et to any large extent since 1993. It is impossible to predict at this stage whether the rate of loss will cont inue to rise linearly as the ageing process proceeds, or if - as some experts fear (Holdack-Janssen, 2000) - the rate of normal emission might in fact accelerate.

Finally, with regard to our total rate of emission, it should also be borne in mind that (for the very reason that the study vehicles are not ye t sufficiently old) neither the 6.3% figure (normal rate) nor the 8.2% figure (total rate) as yet makes any allowance for possible emission on the occasion of disposing of an

old car.

Despite the limited amount of information obtaina ble due to the small number of cases involved, our study still provides us with a picture of the way in which emission rates vary from one to the other of the three different brands of vehicle. What for me is the most important finding out of Table 9 is not so much the fact that Brand 2 has the highest figures for bot h the 'normal' and the 'irregular' rate of emission (indeed it also comes highest under the heading of loss in grams per vehicle), as the actual existence of a difference of any kind between the brands that is not to be seen when they are viewed as a whole - because this difference suggests the need to leave a little latitude above and below our duly determined average annual rate of emission of 8.2%.

Table 9: Annual Rates of Emissi on and Loss in Grams per Vehicle

for the Three Brands of Car

Vehicle Normal

Emission Irregular

Emission Total

Emission Grams per

Year*

Brand 1 6.2 1.5 7.7 57

Brand 2 7.0 2.2 9.2 79

Brand 3 5.8 1.9 7.7 72

All brands 6.3 1.9 8.2 70 * The respective refrigerant charges are 734 g (Brand 1), 857 g (Brand 2) and 932 g (Brand 3).42



### II. Margins of Error in determined Quantities

Our study could be criticised on fund amental statistical grounds for not being sufficiently representative and its limited informative value. It is fair to say t hat our selection of examined air-conditioning systems is too small, and that it does not re present a systematically collected random sample - a fact which is obvious from the outset given our concentration on 'authorised dealer' workshops, which only service some out of the total stock of air-conditioned vehicles, and furthermore only the 'younger' of them (note the preponderance of vehicles less than four years old).

Acknowledging these shortcomings, in my defence I w ould say that any more representative a survey could not have been completed within the terms of reference provided.

That having been said, however, the study does contai n some inherent sources of error, to allow for which certain correcting factors and margins of error did need to be introduced.

While completing the study, one important source of error emerged in Chapter D in connection with determining the 'normal' rate of emission. Right from the first diagram (Diagram 2), putting "regular" refrigerant loss on a par with "less than 40% refrig erant loss" proved to give an unduly 'black-and-white' picture of the situation, given that a substantial portion of refrigerant losses under 40% are not actually attributable - as initially thought - to 'regular' , but to 'irregular' events. The 'irregular' events were eliminated by a criterion ('more than four times the av erage') the author felt to be plausible at the time, but which proved in the end to be rather arbitrary and could not guarantee that the selection 'corrected' in this manner would then really only include systems experiencing 'normal' leakage of refrigerant. This source of error is necessarily associated with t he adopted procedure of evaluating Refrigerant Record Sheets 'after the event', and in the author's opinion, its influence on the result of the study is impossible to quantify. The error would be avoidable by employing another, in fact far more complex and more time-consuming, empirical approach involving the su rveyor's own controlled measurement and analysis of the refrigerant charges in intact vehicle air-conditioning systems.



### 1. Errors in recording recovery and recharging operations

The general readout-error probability of plus or minus 25 grams works in both directions - upward and downward - by up to 15%.

As discussed in Chapter B, the 50-gram rounding pr actised when writing Record Sheets can give a false impression of emission by an amount of 25 grams above or below reality. Without exception, refrigerant

loss of less than 40% is deemed to be 'normal' emissi on. That 40% is at most 340 grams of the average 850 gram charge quantity. Then, when it is put in relationship with the mid-point between 0 and 40% (therefore with 170 grams), the '25 gr am allowance' is in fact 15%.

Rounding errors have some part to play in the rate of 'irregular' emission too, even if to a very much lesser degree because we are dealing here with 'total ' loss. On top of this come the omitted entries of refrigerant loss, which I estimated to account for at least 5% (C hapter B, Section II, Paragraph 5).



### 2. Differences between the three brands of car

Comparing the three brands of car, both the 'normal' and the 'irregular' rates of emission vary either upward or downward by more than 15% from the average.43



### III. The Annual Rates of Emi ssion w i th Margins of Error

The emi ssi on rates d u ly determine d incl ude 'fault tole ran c e s ' of at least 25% ab o v e and belo w to allow

for inaccu ra ci es of mea s u r ement and to accou n t for the different figure s from the three differe nt car

bran ds in o u r study. The s e margi n s a r e il lustrate d grap hically in Dia g ram 1 1

.



### A nnua l N o rma l

, I rre g u l a r a n d T o t a l R a t e s o f Emi s s i o n o f R

- 134a

fr o m C a r A i r
- C o n d itio n i n g S y stem s u p to S e v e n Y ear s o l d (25%

m a r g in o f er r o r - n o t in clu d in g 2% em issio n o n d i sp o sal)

6,3

1,9 8,2

0 2 4 6 8 10 12



### No r m a l-E R I r r e g u l. E R Ov er all-E Rpercent

Diagram 11: Annual rates of 'normal ' , 'irregul ar' a nd 't otal' emissio n from ca r air-con ditioning systems at most seven years old - with 25% margi n of erro r and excludin g an approxim atel y 2% annual rate of

emission o n disp osal. The total rate of 8.2% is made up of the 'normal' rate (6.3 %) and the 'irregul ar'

rate of emissi on (1.9%) a d ded togeth e r. Our exam in a t ion proved th e need to allo w a 25% margin of

error ab ove a nd belo w , so the 'total' rate fluc tuates within the regi on of 6.2 to 10.3%.

Allowing fo r the ne ce ssary 25% margin of erro r abov e and bel ow t he line, the 'total' rate for a i rcon d itioning systems u p to seven yea r s old varie s (without incl udin g loss on di sp osal ) betwee n 6.2%

and 10.3%. Current total emissi on of R-134a fro m ca r air-co ndition ing system s i n the year 20 00 ca n be

confin ed withi n the limits of 685 and 1,1 4 0 tonne s, these differe nt figure s de pen d i ng on wheth e r an emission rate of 6.2% (the minimum ) or 10.3% (the m a ximum) is a s sumed fo r the 11,500 ton n e s of refrig era n t in circulatio n in passe nge r ca rs in G e rm an y. These 11,5 00 tonne s are base d , in turn, on the assumptio n o f 13 million air-con d itioned passe nge r ca rs (30% of the total popula t ion being thu s equip ped ) ha ving an avera ge R-134 a ch arge of 85 0 g

.



### IV. Emission on Disposal raises the Annual Rate to 10 %

It is worth re membe r ing at this point tha t an annual ra te of emissio n extending o v er the first seven years of a system's use will be quite different (l ower, in fa ct) from an annual emission rate cal c ulated over the

whol e life of a system. Fact ors to b e men t ioned in this con n e c tion would first of al l includ e the agerelated a c cel e ration of no rmal system le aka ge f eared by some exp e rts (Hol da ck-Ja n sse n - 20 00, and44

others), an aspect neither examined nor quantified within the confines of the pres ent study in which the

rate of normal emission remains at 6.3%.

A more important aspect is the loss associated with the scrapping of old cars. Weaknesses in this respect do not lie with German recyclers of old cars , who by this stage are very largely equipped with proper refrigerant recovery stations. Indeed, the si tuation is likely to improve even further over the coming years, thanks to national and EU regulation. The weak point is the fact that the approximately 1,400 recyclers in Germany receive not even the half of the 1.3 to 1.5 million old cars taken out of circulation (Arge Altauto 2000, 34). A bout half of the cars from any original German 'year of registration' are first exported as used cars to countries outside of the EU (Arge Altauto 2000, 48). I know nothing about refrigerant recovery in the importing countries, but it probably does not carry any great weight in practice, an assertion which would admittedly need to be examined. An investigation of this kind is called for, in that evidently "all western European st ates" (ibid.) are faced with this export problem.

If we were to say that an air-conditioned old car still contains 50% of its standard charge of refrigerant, and if we were then to assume, crudely speaking, a figure of 100% recovery of refrigerant under German recycling conditions and none at all for exported vehicles, then 25% of the refrigerant associated with a whole 'year of regi stration' would remain un-recovered.

Interestingly, Pettersen/Hafner published 75% as a maximum level of recovery from R-134a airconditioning systems as early as 1996, a figure that has not been refuted to date. Tujibayashi arrived at something in the same order of magnitude (70%) for the island state of Japan in 1999, as a goal to be aspired to by the year 2010.

Distributed over a car air-conditioning system life of tw elve to thirteen years, loss at disposal produces an increase of 2% in the annual total rate of emission. That rate therefore fluctuates within the region of 10% unless the situation should change su bstantially within the medium term.

The risk of an incorrect estimate increases very c onsiderably once the 'first seven years' period has elapsed.

In any case, precise figures are not the goal of the present study, and never were, the prime purpose having been to arrive at the order of magnitude of emission from ex-works R-134a air-conditioning systems which are seven y ears old at the most.

I feel the study has duly achieved its aim by localising this order of magnitude within the region of 6 to 11%, or, including emission on disposal, 8 to 13%.45



## G. The Question of Reducing Emission by Regular System Inspection

All manufacturers of air-conditioning systems re commend regular maintenance (Air-Conditioning Conference - 2001). However, these systems are not included in the scope of the vehicle inspections specified by the car manufacturer s. Preventive maintenance is carried out on a voluntary basis and therefore rarely, although many garages do o ffer the service of checking an intact air-conditioning system along the lines of the description in the box below.

Air-Conditioning System Check (as recommended by WAECO)

Every twelve months

Function check: high and low pressure r eadings, condenser fan, temperature of air blown into passenger compartment.Visual inspections: soiling of or damage to the condenser, fault location on airconditioning system using leak indicator unit.

Every twenty-four months

Replace dryer Recover and clean refrigerant, dehumidify system at same time. Recharge up to standard level.



### I. Maintaining an Air-C onditioning System increases Operational Reliability

Checks in which the refrigerant circuit is not opened can provide clues to faults and may improve the efficiency of a system where a contaminated condenser is cleaned in the process, for example. Attention of this kind to the condenser may reduce fuel consumption, thus contributing to climate protection. Severe loss of refrigerant may well be susp ected if pressure levels are too low or if the temperature of the air leaving the evaporator is too high, but the probl em cannot be rectified for as long as the system remains unopened. There is little sense in looking for leaks in a closed, intact system, because normal emergence of refrigerant through hoses an d seals will neither be detected nor eliminated in the process. In turn, a check of this kind is unnecessary in respect of irregular leaks, because lack of refrigerant will already have brought t he system to a standstill.

Checks in which the refrigerant circuit is opened in an intact system make more sense from the technical point of view. The refrigerant is duly cleaned (dehumidified, that is) in the recovery/recharging station, and the emptied system is dehumidified by vacuum at the same time. The dryer may be changed to ensure continued absorption of diffusi ng humidity once the system is closed up again. Finally, recharging prevents operational faults attri butable to loss of refrigerant. Provided no irregular damage occurs, the cleaning and recharging of refrigerant does help to improve functional reliability.

However, the possibility that measures of this kind might prevent effective emission of refrigerant is quite another question

.



### II. Regular Maintenance generally does not reduce Emission

This question needs to be examined individually with regard to the different forms of emission.46

Emission on disposal can only be avoided where the refrigeran t is properly removed when a car is scrapped - the question of reduction by means of regular maintenance with a top-up of refrigerant does not apply to this class of emission (rather more the reverse, in fact, since an air-conditioning system which is not properly pumped dry during the scrappin g process will emit more if it had been topped up and remains full, than it would if it were half empty).

The same applies to irregular emission caused by an accident or by stone impact, since regular maintenance will not prevent external damage to t he air-conditioning system accompanied by abrupt emergence of refrigerant.

Normal emission consists mainly in leakage of refrigerant through seals, a factor inextricably linked with the present-day design of ai r-conditioning systems wh ose compressor is driven by the vehicle's engine (see Chapter D, Section 6). Regular refriger ant top-ups (calling for the system to be opened) may recurringly put off the day on which refrigerant shortage begins to cause operational problems, but they do not help to reduce emission.



### III. Partial Prevention of I rregular Emission - Minimal

Nonetheless, suppliers of recovery/recharging stat ions have put forward two examples demonstrating how they think that emission could be reduced by ma intaining a system regularly and checking it for leaks (Recovery/Recharging Station Conference - 2001) . Both of these examples relate to 'irregular'

emission.



### 1. Two examples showing how emission may be reduced by maintenance

Example 1: where the refrigerant is not regularly cl eaned, penetrating moisture may overcome the absorbent capacity of the dryer and mix with fluori nated refrigerant to produce corrosive acids (HF) which cause internal corrosion and leaks in metal components.

Example 2: a leak, whether attributable to internal or exte rnal causes, may initially be so small that the amount of refrigerant escaping is still too slight to be noticeable as a fault. Over time, however, the leak grows and grows in size and may eventually become su fficiently large to let through the whole charge of refrigerant. This emergence of refrigerant would be confined by checking for leaks in good time.



### 2. Internal corrosion by acid refrigerant is unlikely

The experts have dismissed the first example (Air-Conditioning Systems C onference - 2001), stating firstly that the capacity of the drye r is designed so that, for the whole life of the system, it will absorb the moisture that penetrates under normal operation, and secondly, that any irregular admission of moisture to the refrigerant circuit to produce a non-evaporat ing liquid would so severely damage the compressor by 'liquid shock' that this component would fail well before acid could form. Rather than a release of refrigerant, the outcome would be a visit to the workshop to have the refrigerant circuit opened with a view to replacing the compressor.

So with regard to Example 1, while regular dehum idification (and recharging) of the refrigerant is undoubtedly a good way of enhancing a system's reliability, regular inspection does not prevent 'irregular' penetration of moisture. Where moisture does penetrate 'irregularly', the occurrence makes itself felt not through loss of refrigerant, but as ( non-emissive) component defect, interfering with the airconditioning system's operation and therefore causing it to be opened in the workshop in any case.47



### 3. Detection of slowly growing small leaks

The second example gives rise to the fundamental question of how large a leak has to be before it can be found in the course of a regular examination.

The principal form of emission - normal emergence of refrigerant through intact seals - is too slight to be found by manually operated leak detector on an un opened system. The detector will only respond to larger-scale leaks, by which stage the operation is ge nerally too late. The only reliable way of looking for leaks is to open the system first. There are two methods of location when this is done.

The first method is to charge the emptied system with li quid nitrogen, metered by pressure reducer from a gas cylinder (kept at 200 bar pressure) into the system, where it develops pressure of up to 20 bar and higher in order to simulate extreme conditions. The leak detector then has a chance of locating leaks which otherwise, under normal workshop conditions, would let out too little refrigerant to be perceptible.

The second method - more frequently used because less complex - is to add a contrast medium or 'tracer' when recharging the system with refrig erant (see Chapter B, Section III, Paragraph 2). The pressure in the system does not rise as high as wh en adding nitrogen, so if the leak is not immediately revealed by a coloured stain (visible under ultraviole t illumination), the driver is asked to call again at an appointed date, when his air-conditioning system is run under practical conditions and the source of

emission becomes clear to see.

To return to Example 2, neither the nitrogen method nor the tracer method 20 are suitable means of finding 'normal' leakage through intact seals. There woul d also be little sense in replacing intact seals, new ones would not necessarily reduce the pace of refrigerant emergence. However, both methods lend

themselves to the detection of "irregular" sources of emission.

Irregular leaks, responsible for just under 2% of annual emission from air-conditioning systems (at most seven years old), are generally associated with abrupt rather than 'creeping' emergence of refrigerant. Within less than a month of being damaged on the out side by a thrown stone, a condenser will have begun to leak so badly because of pitting that hardly any refrigerant will be left in the system (Haussmann, 2001). Refrigerant emerges abruptly in any case after a frontal collision involving body damage. Accidents and stone impact are by far the most frequent causes of 'irregular' loss of refrigerant (see Chapter C, Section I). Generally, too, where other components develop leak s for irregular reasons (compressors, evaporators, dryers), t he pattern of damage will be fast-acting to precipitate by nature, for instance when a compressor breaks or a dryer cracks.

It can indeed arise that a hole will enlarge continuously but so slowly that it fails to interfere with the system's operation by the time of the next regular inspection, which may be six months away or as far as two years into the future. However, such a situation is the exception to the rule among cases of 'irregular' damage, which for the most part cause refr igerant loss in such a short space of time that

established maintenance interv als of two or four years will intervene either too early or too late in time. The vehicle has to be brought into the workshop without delay.

20 Since the tracer dye bonds to the refrigerant oil, not the refrigerant itself, no stain will form where a leak is so small that only gas can pass through, not oil.48



### 4. Emissions prevented or caused by maintenance are approximately equal in magnitude.

It may be broadly assumed that 15% of cases of 'irr egular' emission comprise leaks of a slowly developing nature which do not interfere with sy stem operation before an inspection, but which are nonetheless found during the inspection. Under this assumption, the emission prevented in the process comes to about 0.2% of the total annual loss of refrigerant. That percentage, related to the 11,050 tonnes of refrigerant in circulation in the year 2000 (13 million R-134a air-conditioning systems each containing 850 grams of refrigerant), corresponds to at most 22 tonnes of emission prevented per

annum.

Against that there is the enormous effort and expen diture of opening 6.5 million air-conditioning systems per year where regular maintenance is arranged once every two years (the interval cannot afford to be any longer if leaks of this kind are to be located in good time).

It should be duly noted that the 2 grams of rechar ging loss normally accompanying each maintenance service (see Chapter B, Section III, Paragraph 1) adds up to 13 to nnes per annum, on top of which

service-related losses in the order of 0.1% 21 or 10.4 tonnes may arise where a leak is not found during the first visit to the workshop.

Consequently, the level of emission which maintenance prevents is almost exactly the same as the level it produces.

As overall outcome , regular maintenance generally does not prevent direct emission of refrigerant, although it may enhance a system's operational relia bility and save on fuel consumption. At a more detailed level, our study describes two particular, conceivable cases demonstrating that regular maintenance either does not prevent refrigerant loss, or does so only at the price of emissions of just the same magnitude attributable to the maintenance operation itself.

21 This percentage rate is derived from the present study, based on the figure of 20.5 kg (from 29 cars) in relation to 21,300 inspections of air-conditioned cars by the nine garages.49



## Acknowledgements, Reference Material

Before all else, I would like to thank cordially Mr Matti Vainio on whose initiative this study has been translated from German into English, by the st aff of the European Commission (DG Environment).

Throughout the course of this study, the author exchanged opinions with Jochen Harnisch of the ECOFYS, whose ideas and suggested alterations have been duly taken on board almost without exception. A special debt of gratitude is due to Mr Harnisch for his most valuable assistance.



### Note on unnamed sources

Unfortunately, the study's most im portant sources of information c ould not be named without revealing the identity of the three selected brands of car. This is a pity, in so far as our study has really been based not only on the Record Sheets, but also - indeed above all - on the experience of the airconditioning mechanics from our nine garages. Serv ice managers, environmental and safety officers, trainers and sometimes managing directors were as much involved as the ap prentices who transferred the necessary data from the garage computers. The assistance prov ided by the sales departments of the three car manufacturers was just as indispen sable, as were the information and suggestions originating from company head offices. While exte nding my heartfelt thanks to each and every one of my sources, I really must mention four particular c ontributors at this point, even if in abbreviated form: Mr F and Mr S of Garage L, Mr P of Garage V, and Dr. M representing one of the three manufacturers.

The author himself must of course accept full responsibility for the actual content of this study.



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