# Disposable Container Heel Testing Study Report

Prepared for: United States Environmental Protection Agency Stratospheric Protection Division 1200 Pennsylvania Avenue, N.W. Washington, D.C. 20460

Prepared by: Perrin Quarles Associates, Inc. 675 Peter Jefferson Parkway, Suite 200 Charlottesville, VA 22911
Under Subcontract to Stratus Consulting, Inc. Task Order No. 11 Contract No. EP-W-06-010

March 21, 2007March 21, 2007

Table of Contents Page Summary ........................................................................................................................ ............. S-1 1. Background and Report Contents .......................................................................................... 1 2. Test Procedures ........................................................................................................................ 1
2.1 Small Ca n Testing

................................................................................................................ 1
2.1.1 Equipment

..................................................................................................................... 1 2.1.2 Test Conditions

......................................................................................................... .... 3 2.1.3 Heel Test Procedure

..................................................................................................... . 5
2.2 Thirty Pound Cylinder Testing

............................................................................................ 7
2.2.1 Equipment

..................................................................................................................... 7 2.2.2 Heel Test Procedure

..................................................................................................... . 8 3. Results and Observations ........................................................................................................ 8
3.1 Small Cans

................................................................................................................ ........... 8
3.1.1 Heel and Charging Time

............................................................................................... 8 3.1.2 Charge Kit Observations

............................................................................................. 11 3.1.3 Observations of System Conditions at Full Charge versus Partial Charge

.............................................................................................................. 14
3.2 Thirty Pound Cylinder Heel Results

.................................................................................. 16 4. Heel Emission Estimates ........................................................................................................ 16
4.1 Small Cans

................................................................................................................ ......... 16 4.2 Thirty Pound Cylinders

.................................................................................................... .. 20 5. Practices to Minimize Disposab le Container Heel Emissions ............................................ 20
5.1 Small Cans

................................................................................................................ ......... 20 5.2 Thirty Pound Cylinders

.................................................................................................... .. 22 References ..................................................................................................................... ............... 23 Appendix A : Thirty Pound Cylinder Transfer Study ........................................................... A-1 Appendix B : Student Survey Results ...................................................................................... B-1Heel Study Report March 21, 2007 Page ii
List of Figures Page Figure 1 : Ford Focus Front End Clip with Recovery/Recycling Machine and Shop Fan

.................................................................................................................. 2 Figure 2 : Small Can with Charge Kit a nd Adapter Installed on the Ford Focus Accumulator Service Port

.............................................................................................. 3 Figure 3 : Diagram of MVAC Systems

.......................................................................................... 5 Figure 4 : Thirty Pound Cylinder on Scale

..................................................................................... 7 Figure 5 : Comparison of Can Heels by Charging Method and MVAC Type

............................... 9 Figure 6 : Percent Can Heels Based on Upri ght Scenario (Gas Phase Charging)

....................... 10 Figure 7 : OT Systems: Charge Time Comp arison with Can Rotated 0 to 90 Degrees (Mean and Range)

........................................................................................................ 11 Figure 8 : Example of Charge Kit Pressure Gauge with System Charge Ranges

........................ 12 Figure 9 : Charge Kit Leak Locations

........................................................................................... 13 Figure 10 : Panel Vent Temper ature Readings -- At Least Five Minutes of Charging

................ 15 Figure A-1: Scatter Plot of Relative Accuracy and Weight Transferred

................................... A-3Heel Study Report March 21, 2007 Page iii

List of Tables Page Table 1 : Small Can Test Scenarios

............................................................................................. ... 4 Table 2 : Small Can Test Data Collec tion (Recorded Every Five Minutes)

................................... 6 Table 3 : Empty 30 Pound Heels

................................................................................................. . 16 Table 4 : Average Small Can Heel Ba sed on Time and Can Orientation

..................................... 17 Table 5 : Annual Emission Estimate Scenarios

............................................................................ 19 Table A-1: Transfer Run Cycle Parameter and Recovery Results

............................................... 2 Table A-2: Recovery/Recycli ng Machine Relative Accuracy

...................................................... 2 Table B-1: Student Survey Results: May 2006 Classes

........................................................... A-1Heel Study Report March 21, 2007 Page iv

[This page intentionally left blank.]Heel Study Report March 21, 2007 Page S-1 Summary In 2006, the U.S. Environmental Protect ion Agency commissioned the Universal Technical Institute in Avondale, Arizona to conduc t tests to determine the amount of refrigerant remaining in do-it-yourself (DIY) small cans 1 and professional 30 pound cylinders used to charge motor vehicle air conditioning (MVAC) syst ems. Industry experts within the Mobile Air Conditioning Aftermarket Parts and Service Equipment Partnership (MACAPSEP) helped develop the testing protocol, pr octor the study, and provi de peer review of the draft report. Comments from the reviewers were considered in this final report. 2 Under typical situations, any refrigerant rema ining in disposable c ontainers after charging a MVAC system is eventually released to the a tmosphere. The releases are referred to as "heel emissions." For small cans, the tests analyzed the heel remaining after various charging times under different scenarios. The tests of 30 pound cylinders quantified th e heel remaining in cylinders that had been removed fr om service as "empty." This re port analyzes th e results of the disposable container tests, provi des a range of annual emission estimates based on those results, and examines potential best practices for DIY and professional chargi ng of MVAC systems to reduce unnecessary MVAC refrigerant emissions. The testing results provide a few key findings:

● The most important factor regarding the rema ining heel of small cans is whether the doit-yourselfer (DIYer) transfers the refrigerant in a gas or liquid phase when charging the MVAC system. When a DIYer holds a can upright , the refrigerant will tr ansfer as a gas. The test results showed that this transfer is difficult and can take as much as 90 minutes to empty a can and minimize the heel. If the DIYer holds the can upside down, the refrigerant will transfer to the MVAC system as a liquid, and the cans tested under these conditions emptied in five minutes. The tests also analyzed slowly rotating a can from an upright to 90 o position repeatedly so that the refri gerant transfers in both the gas and liquid phases. The tests showed that the small cans generally emptied within 5 - 15 minutes under that approach.

● The information and equipment available to DIYers are usually too limited to allow the owner to know how much refrigerant to add or when the system is fully charged. This uncertainty can lead to ineff ective use of small cans and increased heel emissions, as well as improper charging of the MVAC system.

● Although the 30 pound cylinders from service sh ops already have low heel levels, new recovery procedures can reduce the cylinder heels further.

1 While sold as a retail product to the general public, service stations also use small cans for some air conditioning

servicing. This report refers generally to the use of small cans by DIY consumers, but acknowledges that service station use is also part of the refrigerant market served by small cans.

2 A separate report summarizes the comments and the response to each substantive issue raised (PQA, 2007).Heel Study Report March 21, 2007 Page S-2 The small can tests produced a wide range of observed heels based on the different transfer procedures that a DIYer can use. This paper presents a range of small can emission estimates based on different transfer procedure sc enarios. For example, based on an informal survey of student technicians, 75% would ch arge an MVAC system holding the small cans upright for a total system chargi ng time of 5 to 10 minutes. Unde r that scenario, the estimated average discarded can heel could be as high as 52%, which would result intotal national annual emissions of 12.5 million pounds. If DIYers inst ead used the rotation method or other flow control method to transfer the refrigerant as a mi x of gas and liquid or controlled liquid for the same 5 to 10 minute period, the average heel would be about 10 to 12% (with total annual emissions of about 2.2 to 2.9 million pounds). If the DIYer increased the transfer time up to 15 minutes, the heel could be reduced to about 1.6%. The estimated annual emissions from discarded 30 pound cylinders are 0.4 million pounds, based on an average heel of 1.85% in the tested cylinders. As the test results and emission estimates show, practices to minimize small can heel emissions can have a large impact, especially if a DIYer charges an MVAC system with small can refrigerant in a liquid (or ga s/liquid mix) phase. However, liquid charging (or a mix of gas and liquid charging) has the potential to damage an MVAC compressor, if the liquid enters the compressor inlet port. This report recomme nds that the industry and other MACAPSEP members examine whether they can develop guidelines to provide for the use of a mix of gas and liquid charging, or other liquid fl ow control method, for DIY small cans. These guidelines must address compressor damage and any other operational or safety concerns. Assuming that those guidelines are feasible, a set of best practices would involve: (1) mixed gas/liquid or flow controlled liquid charging to reduce the heel em issions; (2) charging for up to 15 minutes to empty each can fully; and (3) DIYers (or professionals) limiting small can use to charging already empty systems or profe ssionally evacuated systems, so that they know how much refrigerant they should use. Service shops currently have the equipm ent to minimize the heel in empty 30 pound cylinders, so the resulting emissi ons from this sector are relati vely small. A new Society of Automotive Engineers standard (J2788) approve d in 2006 may further reduce heel emissions by improving the performance of HFC-134a rec overy/recycling equipment and practices.March 21, 2007
Disposable Container Heel Testing Study Report

1. Background and Report Contents Government and industry representatives formed the Mobile Air Conditioning Aftermarket Parts and Service Equipment Pa rtnership (MACAPSEP) in May 2004 to reduce unnecessary MVAC refrigerant emissions. Members of MACAPSEP are the U.S. Environmental Protection Agency (EPA), the California Air Resources Board, Automobile Aftermarket Industry Association (AAIA), mo tor vehicle air conditioning (MVAC) service equipment companies, chemical companies, can manufacturers, can fillers, and can retailers. Current MVAC systems use HFC-134a (1,1,1,2 Te trafluoroethane) refrigerant. MVAC refrigerant emissions can come from leaks in th e system, from servicing, and from end-of-life disposal. Servicing emissions can occur either at professional repair shops or through do-ityourself (DIY) servicing. Repair shops ge nerally use 30 pound cylinders and refrigerant recovery/recycling machines that minimize emi ssions. Do-it-yourselfer s (DIYers) use small cans (typically 12 ounces) of refr igerant to recharge or top o ff an MVAC without the aid of certified service equipment. As part of MACAPSEP's emission reduction efforts, EPA commissioned the Universal Technical Institute (UTI) in Avondale, Arizona , to conduct testing to produce data on the potential for disposable contai ner heel-related emissions. The small can tests measured the amount of refrigerant remaining in a 12 ounce co ntainer after directly charging the container contents to an MVAC system. The 30 pound cyli nder tests measured the amount of refrigerant remaining in the cylinder after a service shop ha d determined it was empty and had removed it from the charging equipment. Ward Atkinson of Sun Testing Engineering and Ken Adams of the Technical Chemical Company proctored the tests. Section 2 of this report outlines the test pr ocedures in detail. Section 3 provides a summary of the test results. Sections 4 and 5 then examine what the potential heel-related emissions may be and how DIYers and professional service stations can improve their practices to reduce heel emissions.
2. Test Procedures 2.1 Small Can Testing 2.1.1 Equipment The small can study used two vehicle front end clips with production MVAC systems and engine components representative of current or ifice tube (OT) and thermal expansion valve (TXV) MVAC systems. Figure 1 shows a 2004 Fo rd Focus front end clip that had an OT system. The TXV system was tested using a 2004 Hyundai front end clip.Heel Study Report March 21, 2007 Page 2

Figure 1: Ford Focus Front End Clip with Recovery/Recycling Machine and Shop Fan
The UTI technicians used the same brand of commercially available 12 ounce can and charge kit throughout the tests. The kit included a can tap and recharge hose with pressure gauge. The can and kit were used with a low si de service port adapter that provided continuous system pressure readings. The can, kit, and adapter appear in Figure 2. The technicians used the same recovery/recycling machine to remove and evacuate refrigerant in the MVAC before each can test (shown in Figure 1). Then, if necessary to establish the appropriate test c onditions, they used the machine to charge the system with a specific amount of refrigerant to represent differe nt levels of a partially full system. After determining that a can was empty, the technicians recovered the final refri gerant heel using the recovery/recycling machine. The tests also used a calibrated high side and low side pressure gauge and hose to measure high and low side pre ssure during the testing, and a calibrated scale with a readability of 0.1 grams (0.001 ounces) and a range of 2,000 grams to weigh the cans before, during, and after the test runs.Heel Study Report March 21, 2007 Page 3

Figure 2: Small Can with Charge Kit and Adapter Installed on the Ford Focus Accumulator Service Port

2.1.2 Test Conditions The tests involved both controlled and vari able conditions. During the tests, the MVAC system controls were set to operate at the maxi mum cool and highest fan settings, with outside air and the compressor operating. The test proc tors maintained the work area temperature at approximately 70 to 75 o F. The UTI technicians tested at least four cans under each scenario. Table 1 summarizes the variable test c onditions under each test scenario. The most important variable is can orientation because it affects whether a DIYer transfers the refrigerant in the liquid or gas phase. The cancontents will transfer more quick ly as a liquid than as a gas. A can held upside down (can opening pointed do wn) will transfer liquid refrigerant, and a can held upright will transfer the refrigerant as a gas. The tests used three different can orientations: (1) upright can (gas phase charging, and the pos ition generally recommended by suppliers); (2) upside down can (liquid phase charging); and (3) slowly rotated can (from 0 o upright to 90 o from vertical), which provides a mix of gas and liqui d phase charging. The te chnicians did not follow any specific procedures with respect to the rate of motion and number of can rotations per five minutes of charging time. The technicians did not c onduct tests of TXV systems with cans in the upside down position because liquid entering the TXV system co mpressor inlet could damage the compressor. Figure 3 shows the layout of components and refrige rant flow in the OT and TXV systems. InHeel Study Report March 21, 2007 Page 4 an OT system, the low pressure port is on or ups tream of the accumulator, which separates liquid refrigerant before the compressor. A similar re servoir is not present in the TXV system. The technicians did conduct tests on TXV systems with the rotated can orientation. The rotation method relies on the liquid refriger ant portion of the charge flashing off in the system before the inlet of the operating compressor.

Table 1: Small Can Test Scenarios
MVAC System(s)

Tested 1 Can Orientation (Charge Phase) System Start State Shop Fan 2 Engine Speed 3 Can Agitation 4 OT and TXV Upright (gas phase charging) Empty system 0 in. Hg Off Idle No

OT and TXV Upright (gas phase charging) Partial charge (1/2 full) - 12 oz. Off Idle No

OT Upside down (liquid phase charging) Empty system 0 in. Hg Off Idle No

OT Upside down (liquid phase charging) Partial charge (1/2 full) - 12 oz. Off Idle No

OT and TXV Rotate 0 - 90 o (mixed phase charging) Empty system 0 in. Hg Off Idle Yes

OT and TXV Rotate 0 - 90 o (mixed phase charging) Partial charge (1/4 full) - 6 oz. Off Idle Yes

OT and TXV Rotate 0 - 90 o (mixed phase charging) Partial charge (1/4 full) - 6 oz. On 1,500 rpm Yes

OT and TXV Rotate 0 - 90 o (mixed phase charging) System evacuated - 29 in. Hg On Idle Yes

OT and TXV Rotate 0 - 90 o (mixed phase charging) System evacuated - 29 in. Hg On 1,500 rpm Yes

Notes:

1 The upside down can orientation with liquid phase ch arging was done only with the OT system because of

risk of compressor damage from liquid slugging. 2 AAIA suggested adding a fan to the test scenarios to simulate air blowing through the car grille. 3 AAIA recommended the 1,500 rpm scenario, because the engine speed affects the compressor operation.

The compressor operating time is a direct result of the MVAC system evaporator freeze protection device. The compressor operating at a higher speed changes the cycle rate. For example, at idle the compressor may not cycle or have a very long period of operating time and a short off time. At higher speeds the compressor on and off times can change greatly due to the evaporator freeze protection control. 4 At least some DIY instructions direct the user to shake the cans to mix the can contents before and/or

during charging. The only can agitation provided during the test scenarios was the slow 0 to 90 o rotation.Heel Study Report March 21, 2007 Page 5 (a) Orifice Tube (OT) System

(OT)

Air Flow

low ( i Condenser

Expansion Device

Accumulator/ Dryer Evaporator Engine-Driven Compressor Front-End

Evaporator Air F Outs de Air or Recirc.)
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Receiver Dryer

Evaporator Expansion Valve (TXV) Engine-Driven Compressor Front-End

Evaporator Air Flow (Outs r or Rec rc. Figure 3: Diagram of MVAC Systems (Adapted from Hendricks, 2001)

2.1.3 Heel Test Procedure The UTI technicians preheated each MVAC system for 15 minutes by idling the engine with the hood open. Preheating took place at the st art of the test day and after lunch breaks. Before each can run, the recove ry/recycling machine evacuated the MVAC system to removeHeel Study Report March 21, 2007 Page 6 any refrigerant and hold a vacuum of 29 in. Hg for 30 minutes. After the evacuation, depending on the test scenario, the technician s either (1) charged the system with 6 or 12 oz. of refrigerant using the charging feature of th e recovery/recycling machine; (2 ) opened the system and allowed it to reach atmospheric pressure; or (3) used th e service equipment to obtain a vacuum level in the system. The technicians weighed full cans and cans conn ected to the charge kit hose and gauge. To start the run, they connected the high side pressure hose and cal ibrated pressure gauge to the high side port, and then connected the special low side adaptor and charge kit/can to the low side of the MVAC system. The low side adaptor was connected to a calibrated pressure gauge. After connecting the low and high side hoses, they turn ed on the engine and ran the engine either at normal idle speed or at 1,500 rpm, with the shop fan on or off. The hood was open and the air conditioner was turned on to high settings/outside air. To initiate charging, the technicians turned the valve handle of the charging hose can tapper to puncture the can, and then opened it to begin charging in the appropriate can orientation. Every five minutes, they disconnected the can and recharge hose from the system, and weighed the small can apparatus. They remo ved any moisture on the outside of the can with a dry cloth before weighing. If the can was not empty, they reconnected the can to the MVAC system to charge for another five minutes (the time to disconnect, weigh, and reconnect was about one to three minutes). This was repeated until the can was empty, or for up to 30 minutes. The technicians determined an empty can by the weight difference and can temperature (a warm can indicating an empty can). Then, they recovere d the remaining contents from the can with the recovery/recycling machine before the final weight measurement. They also collected additional parameters described in Table 2 at fi ve minute intervals during each can test.

Table 2: Small Can Test Data Collection (Recorded Every Five Minutes)

Parameter Recorded Location Measured or Description Temperature Shop and vehicle ambient Vehicle grille inlet air Evaporator inlet air Panel outlet vent air (left, center left, center right, and r ight) Compressor inlet pipe surface Pressure Low side system service port High side system service port Voltage Blower Engine speed Engine (cont.)Heel Study Report March 21, 2007 Page 7 Table 2: Small Can Test Data Collection

(Recorded Every Five Minutes) (cont.)

Parameter Recorded Location Measured or Description Kit gauge color Recorded gauge color Compressor cycling Yes/no Can temperature Cold/warm Shop fan operation Yes/no Air selection Always OSA (outside air)

2.2 Thirty Pound Cylinder Testing 2.2.1 Equipment The UTI Training Facility conducted heel te sts of six 30 pound HF C-134a cylinders from the facility's training shops. The tested cylinde rs (Figure 4) had been removed as "empty" from equipment used in MVAC system servi ce activity. Test equipment included a recovery/recycling machine certified to the Society of Au tomotive Engineers (SAE) J2210 standard, a calibrated scale, a pressure gauge, a thermometer, and a heat blanket.

Figure 4: Thirty Pound Cylinder on ScaleHeel Study Report March 21, 2007 Page 8 2.2.2 Heel Test Procedure The technicians conducted the tests at standard room temperatures. They weighed each cylinder before recovery of the cylinder contents, and measured and recorded the initial cylinder pressure. With the recovery/r ecycling machine, they performed two recovery cycles on each cylinder and measured the cylinder weights after each recovery cycle. The technicians pulled a vacuum (10 to 15 in. Hg) during the first recovery cycle. The recovery was completed after the pressure stabilized. They used a different procedure during the sec ond recovery cycle to examine the effects of pulling a deeper vacuum (29 in. Hg). They also applied a heat blanket during the second recovery and orie nted the cylinders upside down to transfer the refrigerant in the liquid phase.
3. Results and Observations 3.1 Small Cans 3.1.1 Heel and Charging Time The charge time required to empty the cans varied significantly ba sed on can orientation, which determines whether the DIYer transfers th e refrigerant in the liquid or gas phase (see Figure 5). The cans held upside down (charging in the liquid phase) were emptied in the shortest time, all within five minutes. The average overa ll charging time to empty a rotated can (mix of gas and liquid phase charging) was 12 minutes fo r the TXV system, with a range of 10 to 15 minutes, and 14 minutes for the OT system, with a range of 10 to 20 minutes. About 80% of the can contents were transfe rred into both systems in the first five minutes. The cans held upright (charging in the ga s phase) did not empty within 15 minutes, or even within the full 30-minute test period (see Figur e 6). In these tests, over half of the can contents were still in the can after 15 minutes, and 26 to 43% of the contents remained after 30 minutes. These results demonstrate how difficult it is to transfer refrigerant in the gas phase. During gas phase charging, the can will get colder, and the colder temperature decreases the can pressure, which in turn reduces the pressure differe ntial that transfers the refrigerant from the can into the MVAC. The reduced pressure differential i nhibits the transfer of the gas from the can to the system. The UTI technicians performed a longer test with one can to determine how long it would take to empty the can in the upright position. They performed the test with the OT system initially empty at atmospheric conditions. It took 90 minutes of upright charging to empty the can contents. In most cases, other factors (such as system beginning state, engine speed, or use of a shop fan) did not appear to have a significant impact on the charge time required to empty a small can. For example, in the upside down can te st scenarios, all the cans emptied within five minutes under all conditions. In addition, for test s on the TXV system that used the rotated can scenarios, all the cans emptied within 10 to 15 minutes.Heel Study Report March 21, 2007 Page 9

0 10 20 30 40 50 60 70 80(%)

id i id i 5 Minutes 10 Minutes 15 Minutes 30 Minutes Charging TimeAverage Can Heel

OT Liqu OT Gas-L qu TXV Gas-L quid OT Gas TXV Gas

Figure 5: Comparison of Can Heels by Charging Method and MVAC TypeHeel Study Report March 21, 2007 Page 10

100

90Average Can Heel (%) OT Atmospheric OT Partial Charge (12 oz) 80 TXV Atmospheric TXV Partial Charge (12 oz) 70

60

50

40

30

20

10

0 5 1 0 1 5 2 0 2 5 3 0 Charging Time (Minutes) Figure 6: Percent Can Heels Ba sed on Upright Scenario (Gas Phase Charging)

The test results did show increa sed variability in some situat ions, although this variability was not as significant as the differences observed based on can orientation. For example, Figures 5 and 6 show that the TXV system tends to charge slightly faster than the OT system. Also, charging an empty TXV system resulted ina substantially lower heel than all other conditions in the upright can scenarios (see Figure 6). This result most likely occurs because of the larger pressure difference between the low side port and the can. Also, the OT system showed some variability in the charging time needed to em pty a can under the rotated can scenarios (see Figure 7). This variability may be related to differences in how often and how quickly an individual can was ro tated, given the critical influe nce of liquid versus gas phase charging. However, the number and speed of can rotations were notcontrolled during the testing. Additional testing with controls on canrotation would be necessary to explore this observed variability further.Heel Study Report March 21, 2007 Page 11

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Figure 7: OT Systems: Charge Time Comparison with Can Rotated 0 to 90 Degrees (Mean and Range)

3.1.2 Charge Kit Observations The charge kit in this study in cluded a pressure gauge to meas ure low side pressure, with color shading to show when the system was undercharged, full, or overcharged with refrigerant (Figure 8). The gauge indicates only the low side system pressure for any given system condition. The system condition is dependent on more than just th e amount of refrigerant in the MVAC system. Therefore, the kit gauge readin g does not provide the information needed to determine the amount of refrigerant in an operating MVAC system. Records of the kit gauge readings during charging demonstrate this limitation. For example, during the empty system scenario for upright can testing, the gauge readings showed that the MVAC system was fully charged for all 30 readings over the 30 minute charge period for the OT system, and for 12 of 30 readings for the TXV system. In both cases, the readings were from operating MVAC systems that were le ss than half full of refrigerant. If a DIYer stopped charging based on the kit gauge readings , he/she would not ha ve a properly charged system and might also discard a can with a larg e heel. Do-it-yourselfer s, however, can use the low side pressure gauge to determine if refriger ant is present in the MVAC system. A low side gauge pressure of zero would i ndicate an empty system.Heel Study Report March 21, 2007 Page 12

Figure 8: Example of Charge Kit Pressure Gauge with System Charge Ranges

The UTI technicians also observed leaks from the hose and coupling of all charge kits used during the tests. The leaks were more ev ident when the assembly became cold during the charging procedure. The rotation of the can during the 0 to 90 o rotation scenarios may have contributed to the observed leak s. The technicians did not m easure or estimate the amount of leakage. Figure 9 shows the observed leak locations.Heel Study Report March 21, 2007 Page 13

Figure 9: Charge Kit Leak Locations a. Hose Leak at Service Port Adaptor

Figure 9: Charge Kit Leak Locations b. Hose Leak at Can TapHeel Study Report March 21, 2007 Page 14 3.1.3 Observations of System Conditions at Full Charge versus Partial Charge Instructions for DIYers sometimes point to the panel vent temperature as a useful indicator of a fully charged syst em for topping off purposes. Instead of using the pressure gauge described in the previous secti on, the DIYer measures the temper ature from one or more panel vents during charging, and stops ch arging either when the temperature is within a certain range or when it becomes stable as the charging progresses. The UTI technicians recorded panel vent temperatures of bot h partially and fully charged OT systems during the tests. These results provide some data on the use of panel vent temperature as an indicator of a full system. After at least five minutes of charging, systems at 60 to 80% of capacity had one vent with temperatures at least as low as those recorded for a fully charged system. Thus, the temperature at a single vent is not a good indicator of a fully charged system.The undercharged systems also showed incr eased variation in temperatures between vents (see scatter plots of the recorded temperature data in Figu re 10). These resu lts suggest that charge kits could recommend that DIYers check more than one vent to determine the system charge. If one vent's temperature is in the proper range, and a ll other vent temperatures are within 10 ° F of that vent, the test data indicate that the system most likely is fully charged. However, the test data do not provide inform ation on vent temperatures for a system that is overcharged. An overcharged system can provi de cooling similar to a full system under the load conditions typical of DIY charging condition s. At hotter weather conditions and operating at road speeds, the system may have elevated hi gh side pressure due to the overcharging, and can reach levels where the compressor will disengage due to a system pressure control, reducing system performance and cooling. Also, at high temperatures an overcharged system may vent excess refrigerant. Thus, further tests with overc harged systems may be necessary to ensure that the charge kit recommendations on vent temperat ure do not suggest procedures that could harm MVAC performance or lead to excess refrigerant venting.Heel Study Report March 21, 2007 Page 15

30 35 40 45 50 55 60l(F)Lowest Pane Temperature

50 60 70 80 90 100 System Charge (%) Figure 10: Panel Vent Temperature Readings -- At Least Five Minutes of Charging a. Lowest Vent Temperature at Different System Charges

0 5 10 15 20 25 30 35)Range of Panel Temperatures (F

50 60 70 80 90 100 System Charge (%) Figure 10: Panel Vent Temperature Readings -- At Least Five Minutes of Charging b. Range of Vent Temperatures at Different System ChargesHeel Study Report March 21, 2007 Page 16 3.2 Thirty Pound Cylinder Heel Results Table 3 shows the heel testing results for each of the six 30 pound cylinders in the UTI test study. The average heel was 1.85%, with a range from 0.302 to 4.46%. The results show that service facilities leave ve ry little refrigerant in dis carded 30 pound cylinders. The heels were similar to those found in the small can te sts with liquid phase charging, and significantly below the levels found in the small can test s that involved only gas phase charging. Table 3 also shows the heel re maining after both the first and second recovery processes. As noted in the procedures section, the first and second recovery procedures were different, with the first recovery performed in the gas phase, an d the second recovery performed upside down in the liquid phase, with a heat blanket and higher vacuum. A separate 30 pound cylinder refrigerant transfer study, also performed at UTI, demonstrates the improved refrigerant transfer by the higher vacuum/upside down/h eat blanket recovery process us ed in the second recovery for each 30 pound cylinder. See Appendix A for a br ief summary of that separate refrigerant transfer study.

. Table 3: Empty 30 Pound Heels

Cylinder Initial Tank Pressure

(psig) Heel % After First Recovery Heel % After Second

Recovery UTI1 53 1.92 1.97 UTI3 25 0.99 1.17 UTI4 Yes 0 4.46 UTI5 Yes 0 1.25 UTI6 0 0 0.302 UTI7 49 1.40 1.98 30 Pound Cylinder Average Heel: 1.85

4. Heel Emission Estimates 4.1 Small Cans The estimated national annual emissions fr om discarding small cans with HFC-134a heels are a product of two variables: average percent heel per discarded can and total annual small can sales. The following section first ex amines scenarios for determining average percent heel per discarded can, and then combines these scenarios with annual sales data to provide a range of heel emission estimates.Heel Study Report March 21, 2007 Page 17 Key factors in determining the average can heel are the charging time and whether the average DIYer transfers refrigerant to an MVAC system in the liquid or gas phase (upright, upside down, or rotated can orientation). Table 4 shows average heels for different can orientations and chargi ng times. The heels were calculated by aggregating the results of all the test scenarios by only can orientation. OT and TXV system data were also combined to simplify the calculation, even though the TXV system tended to charge faster than the OT system . This simplification is balanced by the larger market share for OT systems (approximately 55 to 60%) compared to TXV systems.
Table 4: Average Small Can Heel Based on Time and Can Orientation

Can Orientation Average Charging Time (Minutes) Average Heel (%) Standard Error (%) Upright 5 74.7 1.04 Upright 10 65.1 1.31 Upright 15 57.3 1.43 Rotated 5 20.4 1.80 Rotated 10 3.94 5.13 Rotated 15 1.63 1.56 Upside down 5 1.40 0.09
With a potential heel that ranges from 1.40 to 74.7% based on the can orientation and charging time, the choice of "typical" DIY pr actices will have a large impact on potential emissions. To establish an estimate that reflects relatively poor practices in terms of minimizing heel emissions, this report examines one DIY practice scenario based on small can charge kit directions and a survey of auto t echnician students. Directions w ith small can kits from three out of four suppliers instruct the us er to hold the can upri ght, and one instructs the user to hold the can upside down. Two of the instructions with upright can use include di rections to shake the can before and/or during charging. None of the in structions directs the DI Yer to rotate the can. For charge times, the directions refer to the pressu re gauge reading or vent temperature. The test proctors conducted a student survey of UTI auto technician students inthe classroom. Fiftyseven students from three classes completed th e survey, although not all participants responded to all questions. Of the students, 20 said th at they had used small cans to charge MVAC systems. The survey and results are in Appendix B. When asked how to hold the can (upright, ups ide down, rotate side to side), 28 students said upright, nine said upside down (an approximate 75/25% split). None of the students said to rotate side to side. Fourteen students said th ey would shake the can during charging, and 25 saidHeel Study Report March 21, 2007 Page 18 they would not. As to how long they would charge a system with one can, 13 said for less than 5 minutes, 19 said for 5 to 10 minutes, and none saidthat they would charge for longer than 10 minutes. There was no indication of whether th e students who had used small cans answered differently than the other students. Given the survey results and kit instructions , the first estimate scenario assumes DIYers use only the upright and upside dow n can orientations, with time intervals of 5 to 10 minutes. The survey suggests that about 25% of DIYers will charge systems holding the cans upside down and 75% will charge systems holding the cans upright . These survey result s are consistent with the kit instructions, where only one of four kits reviewed directed the DIYer to charge a system holding the can upside down. This is Scenario 1 in Table 5, which results in about 50% of small can refrigerant usage emitted per year due to the can heel. As noted before, some of the charge kits direct users to shake the cans in an upright position, and a number of the student s surveyed also said that they would shake the can when charging an MVAC system. None of the test scenarios, however , included upright can shaking. The 0 to 90 o can rotation scenarios did provide agitati on, but the can agitation caused by the can rotation to 90 o from vertical resulted in a mix of gas and liquid phase charging. An upright shaken can with a tighter angle of rotation would still result in gas phase charging, similar to the tested upright can scenario without agitation. Therefor e, the upright can assumption in Scenario 1, and not a rotated can assumption, is the closest representation of the likely heel from a shaken upright can. Two other scenarios investigate how emissions might change if DIYers rotated cans from 0 to 90 o , as was done in the test scen arios. The Scenario 2 estimate in Table 5 assumes that DIYers charge MVACs by holding cans in an up side down position for 25% of all cans and by rotating cans from 0 to 90 o for the remaining 75% of cans. The estimate maintains the assumption of an average time of 5 to 10 minutes. Scenario 3 assumes that all charging occurs by rotating the cans for an average time of 5 to 10 minutes. The assumptions in Scenarios 2 and 3 result in similar emission estimates of 10 and 12% of small can refrigerant use per year. These scenarios reduce heel emissions by about 80% from the estimates in Scenario 1.Heel Study Report March 21, 2007 Page 19 Table 5: Annual Emission Estimate Scenarios DIYer Charging

Assumptions Annual Emission Estimates (pounds/year) Scenario 1 - All liquid and all [1.40% x 0.25] upside down + [0.75 x (74.7% + 65.1%)/2] upright = 52.8% average heel gas charging: 25% of refrigerant charged upside 52.8/100 x 11,833 tons x 2,000 pounds/ton = 12,496,000 pounds emitted down for 5 minutes, 75% charged upright for an average of 5 to 10 minutes Scenario 2 - All liquid and [1.40% x 0.25] upside down + [0.75 x (20.4% + 3.94%)/2] rotated = 9.5% average heel mixed gas-liquid charging: 25% of refrigerant charged 9.5/100 x 11,833 tons x 2,000 pounds/ton = 2,248,000 pounds emitted upside down for 5 minutes, 75% rotated 0 to 90 o for an average of 5 to 10 minutes Scenario 3 - Mixed gas-liquid [(20.4% + 3.94%)/2] rotated = 12.2% average heel. charging: 100% rotated for an average of 5 to 10 minutes 12.2/100 x 11,833 tons x 2,000 pounds/ton = 2,887,000 pounds emitted

Note: The annual 11,833 tons/year HFC-134a sales figure for the DIY market is from 2004 sales data from AAIA (Thundiyil, 2005).
The accuracy of the estimated heel emissions in Table 5 is limited by the relatively small survey of charging practices. However, the stude nt technicians surveyed could be viewed as representing, at minimum, a well-informed segm ent of the general popul ation regarding small can charging practices. A randomized internet survey of MVAC DIYers performed by Frost and Sullivan for the Automotive Refrigerant Products In stitute (ARPI) also examined DIY practices. Summary results on DIY charging practices have been made available in PowerPoint form (ARPI, 2006). It is difficult to evaluate those results at this time in the context of this study without further detailed information on the questi ons or on the survey instrument. However, the findings of that report would suggest lower emission estimates than shown in Table 5. To refine the estimates in Table 5, EPA and others could conduct a follow-up, scientif ic survey of DIYers to identify specific common practices. Absent th at data, the estimates in Table 5 indicate the potential for significant emission re ductions if DIYers follow best practices to minimize heels. Another important consideration is that the annual emission estimates in Table 5 are only for small can heel emissions and do not include em issions from refrigerant charged into a leaking system, refrigerant released by improper opening of the system, releases due to overcharging, and leaks from charge kit hoses and connections. Estimates for those emissions are outside the scope of this report.Heel Study Report March 21, 2007 Page 20 4.2 Thirty Pound Cylinders The development of emission estimates fr om 30 pound cylinders reli es on the average heel in a cylinder and the total number of pounds of refrigerant sold annually in cylinders. The estimated heel emissions from discarded cylinde rs are about 0.4 million pounds per year, based on the overall 1.85% average heel for the 15 test ed cylinders and annual 30 pound cylinder sales of 23.3 million pounds of refrigerant per year (Hoffpauir, 2005).
5. Practices to Minimize Dispos able Container Heel Emissions 5.1 Small Cans Given the potential for significant heel emissions from small cans, this study raises an important question: other than taking a car in for professional MVAC servicing, how can a DIYer minimize can heel emissions? The results indicate a set of thre e practices that could significantly reduce these emissions: (1) Evaluate adoption of the can rotation orientation or other flow control methods. In the small can tests, can orientation (liquid, ga s, or a mix of gas and liquid phase charging) had a significant effect on the amount of time required to empty a can while charging. The other test factors (such as system state, higher engine sp eed, and cooling with a shop fan) did not show a significant effect. Liquid phase charging (can upside down) is the fastest method, but can damage the compressor. Thus, individuals should not conduct upside down charging while the compressor is operating. As demonstrated by th e upright can tests, ga s phase charging takes much longer, approximately 90 minutes, to empty the can. The alternative orientation of rotating the can from 0 to 90 o , with a mix of gas and liquid phase charging that in effect cont rols the flow of refrigerant, is reasonably fast and reduces the can heel significantly compared to charging only in the gas phase. The rotated can testing showed an average final chargi ng time of 12 minutes for the TXV system and 14 minutes for the OT system. The can rotation method could reduce the average heel to about 1.6% if done for up to 15 minutes (see Table 4). The rotation method relies on the liquid refrig erant portion of the charge flashing off in the system before the inlet of the operating compressor. Although this method was tested on both TXV and OT systems, there may be the potential for liquid reaching the operating compressor. Three out of the four charge kit instructions reviewed for this report recommend only upright charging, so suppliers may be reluctant to recommend the 0 to 90 o rotation practice. However, if the industry and others working inthe MACAPSEP framework can develop detailed guidelines to protect against possible compresso r damage from liquid refrigerant, the rotation method would offer an approach for DIYers to minimize small can heel emissions. The industry also may need to consider kit equipment cha nges to reduce leaks from the DIYer rotating the can, as well as other operati onal and safety issues outside the scope of this study.Heel Study Report March 21, 2007 Page 21 A possible alternative to the 0 to 90 o rotation practice fo r industry consideration would be to develop a method that incorporates a flow lim iter in the charging kit that would allow upside down liquid charging without compressor damage (PQA, 2007). The flow limiter would provide the same flow control as the 0 to 90 o rotation practice, and would be designed to empty the can while held upside down at a rate that would pr otect the compressor. This would offer a more straightforward and less variable approach than the 0 to 90 o rotation practice. (2) Set a minimum charge time. The second recommended practice is to prescribe a minimum charging time of up to 15 minutes, assumi ng that the DIYer is using the rotated can method or other flow control method and is servic ing an empty or evacuated system. The tests showed that, after 15 minutes, all small cans us ed to charge the TXV system were empty under the rotated can scenarios. For the OT system, u nder most conditions, all rotated cans were empty after 15 minutes, whereas it took up to 20 minutes to remove a slight percentage of additional refrigerant from a few of the cans tested. Th e effectiveness of this recommendation, however, will depend on the willingness of a DIYer to rotate or hold a can for 15 minutes over or near a hot running engine. (3) Charge empty or evacuated systems only. As demonstrated by the charge kit pressure gauge readings, there is no way to tell how much refrige rant is in the system (except that the DIYer can tell that the system is empty if the gauge static pressure is zero). An alternative approach, relying on the panel vent temperatures, may result in improperly charging the system. Thus, the best approach is to limit DIY or professional charging ac tivities to an empty system. A zero static pressure reading can dete rmine whether or not the system is empty. If there is a positive static pressure reading, th en the best way to add the proper amount of refrigerant is to recover refrigerant and evacuat e the system with a reco very/recycling machine, and then charge the amount specified by the manufacturer. Venting the MVAC refrigerant without capture is a violation of EPA regul ations that prohibit the knowing release of refrigerants. To be in compliance, a DIYer c ould have a professional repair shop recover and evacuate the system, and then charge the system by himself or herself. It may be difficult to obtain acceptance of this practice. Continued in dustry testing to develop a reliable means of using pressure and vent temperatures, while a voiding overcharging, may be needed to address this issue. Implementing all of these new practices in combination not only would reduce emissions but could also reduce a DIYer's long-term co sts by avoiding MVAC system damage from improper charging. At a minimum, the practices would help avoid reduced system performance associated with undercharging or overcharging a system. This study did not evaluate these potential non-emission benefits. Further work in this area could assist DIYers inunderstanding the MVAC impacts of improper charging, as we ll as how the practices designed to reduce emissions could help to reduce those impacts. If an MVAC system is already empty, the recommended practices would not affect the DIYer's cost to conduct the service. If the sy stem is not empty, the recommendation that theHeel Study Report March 21, 2007 Page 22 system be professionally evacuated before DI Y servicing would increase the overall servicing costs and discourage this approach. However, the DIYer also may avoid significant additional costs from improper MVAC system charging. Thes e practices also ensure that the DIYer uses all the refrigerant in a can rather than discar ding a can with significant levels of purchased refrigerant still available for use. It is important to note that these practices are solely from the viewpoint of minimizing heel emissions. Further work with industry stak eholders and DIYers will be necessary to tailor these concepts into workable guidelines that gain acceptance by DIYers. In addition, these practices are not meant to reduce emissions from other aspects of DIY servicing, especially the potential emissions from chargi ng a leaking system without fixi ng the underlying leaks. That said, the average small can heel can be reduced to about 1.6% of the orig inal can contents if DIYers follow practices that use a mix of gas and liquid phase charging and charge each can for about 15 minutes. Implementing these practices would reduce annual heel emissions by as much as 97% from the potential heel emissions based on alternative practices that involve primarily gas phase charging for shorter time periods.
5.2 Thirty Pound Cylinders On the professional side, the heel tests f ound that service shops currently have the equipment to minimize the heel in empty 30 pound cylinders. In addition, SAE has approved a new standard J2788 for recovery/recycling equi pment and recovery/recycling/recharging of MVAC systems. This new standard has the po tential for further heel reductions. The SAE J2788 standard supersedes the requirements of SAE's prior J2210 standard. The new, tighter standard requires that the recovery/recycling equipment recover 95% of a system refrigerant charge in 30 minutes or less. This requireme nt will result in new recovery/recycling machines that can pull a deeper vacuum on empty cylinders prior to disposal than do the current J2210 machines.Heel Study Report March 21, 2007 Page 23 References Atkinson, W., Data spreadsheet from Decem ber 2005 empty 30 pound cylinder heel tests performed at the Mobile Air Conditioning So ciety (MACS) Technical Center, August 29, 2006. Automotive Refrigerant Products Institute (ARP I), Prepared for ARPI by Frost and Sullivan, U.S. Consumer Buying Buying Behaviors of R-134a Refrigerant for Light Vehicle Applications, Draft Report, September 2006. Hendricks, T., Vehicle Transient Air Conditioni ng Analysis: Model Development and System Optimization Investigations. NREL/7P-540-30715. National Renewable Energy Laboratory, Golden, Colorado, June 2001. Hoffpauir, E.T., Reducing Refrigerant Emissi ons at Service and Vehicle End of Life, Presentation to the Mobile Air Conditioning Su mmit, Sacramento, California, March 15 - 16, 2005. Perrin Quarles Associates, Inc. (PQA), Summary of External Review of Disposable Container Heel Testing Study Report, Prepared for th e Stratospheric Protection Division, U.S. Environmental Protection Agency, March 21, 2007. SAE J2788 - HFC-134a (R-134a) Recovery/Recycling Equipment and Recovery/ Recycling/Recharging for Mobile Air Conditioning Systems, 2006. Thundiyil, K., Mobile Air C onditioning Aftermarket Parts and Service Equipment Partnership (MACAPSEP), Presentation to the Mobile Air Conditioning Summit, Sacramento, California, March 15 - 16, 2005.Heel Study Report March 21, 2007 Page 24

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Appendix A Thirty Pound Cylinder Transfer Study

A.1 Introduction The Universal Technical Institute (UTI) c onducted a cylinder heel test program that evaluated refrigerant transfer from a 30 pound disposable cylinder that contained about 10% of its original charge. The test program recovered refrig erant from cylinders with low refrigerant levels to evaluate the effectiveness of recovery/recycling machines in transferring the refrigerant under different tran sfer conditions.
A.2 Methods The test program was structured in the sa me manner as the 30 pound cylinder heel study. UTI weighed each cylinder before and after reco very with a recovery/recycling machine. The weight difference determined the amount of refrige rant transferred. UTI tested five cylinders with each transfer method. For the gas transfer evaluation, UTI made three consecutive transfer runs with each cylinder in the upright position, followed by a fina l liquid transfer run. UTI performed the liquid phase transfer with the cylinders in the upside down position, and with a heat blanket heating the lower portion of the cylinder. The liquid tran sfer evaluation consiste d of three consecutive transfer runs with the cylinder upside down and a heat blanket. The technicians added the heat blanket after observing frost on the bottom of the cylinders. Table A-1 outlines the target vacuums and recovery cycle times for each recovery run. At the beginning and end of each recovery run, t echnicians recorded measurements of the time, shop temperature, gauge tank pressure, vacuum, qu alitative tank temperature (touch), and before and after weight measurements. They also r ecorded the amount of ma terial transferred, as measured by the recovery/recycling machine, for the first gas and liquid phase runs. A.3 Results A.3.1 Refrigerant Transfer Table A-1 compiles the average amount of the original cyli nder refrigerant that was recovered after each run, and the average cylinde r heel with the 95% confidence intervals for the averages. The results confirm that it is much easie r to transfer the refrigera nt out of the container in the liquid phase. The average pe rcentage recovered in the first liquid phase run is greater than the total material recovered after three runs in the gas phase (97.7% versus 93.8%).Heel Study Report March 21, 2007 Page A-2 Table A-1: Transfer Run Cycle Parameter and Recovery Results

Recovery Test Transfer Phase Target Vacuum (in. Hg) Target Cycle Time (minutes) Mean of Refrigerant Recovered (% of Original Contents) 95% Confidence Interval of Mean Recovered (%) Mean Cylinder

Heel (%) 95% Confidence Interval of Mean Heel (%) Gas Phase Transfer Gas 1 Gas 10 15 43.6 42.3 to 44.8 6.04 4.95 to 7.12 Gas 2 Gas 29 30 74.4 67.1 to 81.8 4.18 3.82 to 4.54 Gas 3 Gas 29 30 93.8 88.5 to 99.1 2.70 2.02 to 3.39 Gas 4 Liquid 29 10 100

- 0.913 0.116 to 1.71 Liquid Phase Transfer Liquid 1 Liquid 29 15 97.7 95.9 to 99.5 2.33 0.53 to 4.12 Liquid 2 Liquid 29 15 100 99.9 to 100 0.032 -0.031 to 0.096 Liquid 3 Liquid 29 10

- - 0

-

A.3.2 Recovery/Recycling Ma chine Measurement Accuracy The testing identified significant discrepancies between the recovery/recycling machine measurement of material tran sferred during a recovery cycl e and the amount of material transferred based on the before and after weights. Table A-2 lists the relative accuracy for the 10 cylinders in the study, and Figure A- 1 presents a scatter plot of relative accuracy versus the weight of material transferred. Both the table and plot show a negative bias in the machine measurements.

Table A-2: Recovery/Recycling Machine Relative Accuracy

Cylinder Weigh Scale Refrigerant Measurement (oz.) R/R Machine Refrigerant Measurement (oz.) Measurement Difference (oz.) Relative Accuracy (%) F1 21.745 6 15.745 -72 F3 30.370 8 22.370 -74 F9 29.815 23 6.815 -23 (cont.)Heel Study Report March 21, 2007 Page A-3 Table A-2: Recovery/Recycling Machine Relative Accuracy (cont.)

Cylinder Weigh Scale Refrigerant Measurement (oz.) R/R Machine Refrigerant Measurement (oz.) Measurement Difference (oz.) Relative Accuracy (%) F5 30.485 14 16.785 -55 F8 32.480 31 1.480 -5 F2 66.380 58 8.380 -13 F4 62.925 51 11.925 -19 F6 43.745 50 -6.255 14 F7 52.745 36 16.725 -32 F10 56.310 60 6.310 -10

0% 20% 40% 60% 80%

0

i i )l i

-80% -60% -40% -20% 1 0 2 0 3 0 4 0 5 0 6 0 7 0

Refr gerant Transferred We ght (ozRe at ve Accuracy %

Figure A-1: Scatter Plot of Relative Accuracy and Weight TransferredHeel Study Report March 21, 2007 Page A-4 A.4 Conclusions This testing program showed that a liqui d transfer, with the 30 pound cylinder upside down and a heat blanket wrapped around the bo ttom portion of the cylinder, could greatly improve refrigerant recovery from cylinders withlow refrigerant levels. Transferring this amount of refrigerant from a 30 pound cylinder, ho wever, is not typical of normal usage. The tests also indicated problems with th e machine's accuracy in measuring recovered refrigerant amounts. The SAE has recently modi fied the recovery/recycling machine standards to include accuracy specificati ons. Implementation of the new J2788 standard should ensure an appropriate degree of machine measurement accur acy for new equipment when it takes effect.March 21, 2007

Appendix B Student Survey Results

Table B-1: Student Survey Results: May 2006 Classes Responses Class 1 Class 2 Class 3 Question 1 Have you used small cans to charge A/C systems? Yes 10 5 5 No 15 22 2 Question 2 What is the condition of the system requiring change? No pressure 8 1 3 Pressure 0 5 4 Question 3 If there is no pressure in the system, how do you prepare for charging? Just add 1 5 3 Evacuate/add 0 22 3 Question 4 When charging with cans, what position do you hold can? Upright 2 22 4 Upside down 8 0 1 Rotate side to side 0 0 0 Question 5 When charging with cans, do you: Agitate (shake) can 6 4 4 No can movement 0 22 3 Question 6 How do you determine if all refrige rant has been removed from can? Feel liquid movement 0 0 0 Can feels cold 0 5 2 Can feels warm 1 9 5 Can feels empty 4 2 0 Other 0 0 5* (cont.)Heel Study Report March 21, 2007 Page B-2 Table B-1: Student Survey Results: May 2006 Classes (cont.)
Responses Class 1 Class 2 Class 3 Question 7 How much time will you spend charging one can? Less than 5 minutes 4 8 1 5 - 10 minutes 2 11 6 10 - 15 minutes 0 0 0 More than 15 minutes 0 0 0 Question 8 How do you determine if ch arge amount is correct? Weight 0 N/A** 0 Gauge pressure 0 N/A** 2 Cold air out panel vent 0 N/A** 1 Gauge and panel vent 0 N/A** 5 Cannot 19 N/A** 0 Question 9 If refrigerant remains in can, what do you do with the extra refrigerant? Saved refrigerant in can N/A*** N/A*** 4 Vent N/A*** N/A*** 3 Question 10 When charging system with cans, what engine speed? Low speed/idle 3 0 7 High engine RPM 2 17 0 Question 11 When diagnosing A/C system perfor mance, what engine speed do you use? Idle N/A 0 2 High engine RPM N/A 22 5

* Weight and can temperature combination. ** Not available. This question was not asked in this class. *** Not available. There was no count of responses, but listed responses included vent, dispose in trash, evacuate, recover, and save.