Recent Experiences in MAC System 

Development

“New Alternative Refrigerant 

Assessment ”

Technical Update

Enrique Peral-Antunez, Renault

[Chair Person]

9/28/2011
Announcing....

MAC Refrigerant Blend

[MRB]

Cooperative Research Program

[CRP]

9/28/2011
3

MRB CRP Sponsors

9/28/2011
4

GROUP MOTIVATION

1. To investigate use of zeotropic alternative low 

GWP refrigerants for Mobile Air Conditioning to 

meet EU Regulation and obtain credits in the USA

2. To evaluate ways to optimize the balance of 

refrigerant properties for current and future 

application in MAC

3. To evaluate the Life Cycle Energy Consumption

4. To assess options that may increase availability of 

refrigerant to meet Global Regulatory 

Requirements for MAC

5. Expand scope of risk assessment methodologies to 

cover new vehicle types 

9/28/2011
5

CRP Overview

 CRP formed under rules of SAE

 OEM & Tier Ones involved

 Chaired by OEM representative with SAE 

support

 Engage experts with refrigerant assessment 

experience

 CRP focused on technical assessment of 

multiple factors in parallel

 Develop proposals for future SAE standards

 MRB is considering two fluids, AC5 and AC6; 

 Today’s presentation will focus on AC6 owing to 

time constraint, but similar data generated for AC5

9/28/2011
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Why look at two fluids?

AC5

 Very close pressure to 

R-134a/R-1234yf

 Similar capacity

 Mildly flammable 

(similar to R-1234yf)

 Temperature glide 

similar to zeotropic 

fluids used in stationary 

sector

AC6

 Slightly higher pressure 

fluid than R-134a

 Potentially higher capacity

 Reduced flammability 

compared to R-1234yf

 Temperature glide 

larger than currently 

used refrigerants

 Future use in heat pump 

systems

9/28/2011
7

Timing

MRB CRP Timing

2010 2011 2012

Task Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr

Planning

Fault Tree Development

Toxicity Assessment

Performance tests

Flammability

Ignition sources

Refrigerant Decomposition

Permeation Testing

Materials testing

Oil compatibility/etc.

Vehicle Evaluations

Compressor endurance tests

Service and handling

SAE Standards

Final Reports

CRP MRB has virtually completed main part of technical evaluation

9/28/2011

Green=completed

Yellow-To be completed
8

Independent Labs

http://www.exponent.com/

creativethermalsolutions.com/

http://www.sceinc.com/

http://www.haifire.com/

http://www.ilkdresden.de/index.php?L=1 http://www.gradientcorp.com/index.html

Science and Strategies for Safe 

Environments

9/28/2011
9

Glide of zeotropic refrigerants

 When a zeotropic fluid evaporates or condenses the 

composition of liquid and vapour vary as the vapour fraction 

(quality) increases or decreases

 And the temperature changes through the phase change 

process

 The components don’t take turns in evaporating: there is 

always evaporation of all components. 

 Our test results on AC6 clearly show the temperature glide is 

present and clearly show that the heat transfer is not impaired

 Need to consider blending 

tolerance and composition 

effects in assessing flammability

 Methods for assessing this 

exist (ASHRAE)

 We have used these in the 

assessment

9/28/2011
10

Flammability

 R-1234yf flammability risk was assessed in 

previous CRP1234

 Extensive testing was involved

 Flammability risk was considered acceptable by 

CRP and US EPA

 MRB CRP desires to identify a lower or 

ideally non flammable refrigerant

 Assessment items

 Flammability limits

 Flame speed

 Ignition sources

 Decomposition products

 Regulations

9/28/2011
11 9/28/2011

Basic flammability data

LFL vol% UFL vol%

AC5 23°C/50% RH [WCF] 8.25 13.65

AC5 60°C/50% RH [WCFF] 8.35 18.3

AC6 23°C/50% RH [WCF] Not flammable Not flammable

AC6 60°C/50% RH [WCFF] 7.1 11.75

R-1234yf 23°C/50% RH* 6.25 NA

R-1234yf 60°C/50% RH 6.55 12.70

*From ASHRAE submission

Limits in air using ASHRAE-34 apparatus and protocol

Resistance 

in circuit

0 KOhm1000 KOhm

AC5 WCF 5000 4050

AC6 WCF >5000 >5000

R-1234yf >5000 >5000

Minimum Ignition Energy in dry air 

at 23°C [mJ]

WCF=Worst Case Formulation

WCFF=Worst Case of Fractionation, for Flammability

 AC6 burning velocity is lower than R-1234yf

 Heat of combustion for both refrigerants similar to 

R-1234yf
12

AC5 AC6 R-1234yf

Blower resistor No 

Ignition

No 

Ignition

No 

Ignition*

Blower module No 

Ignition

No 

Ignition

No 

Ignition*

12 volt battery cable TBD TBD TBD

Friction sparks No 

Ignition

No 

Ignition

No 

Ignition

Ignition Source Test

9/28/2011

*Based on previous 

testing at INERIS
13

AC5 AC6 R-1234yf

Wire-to-wire short No 

Ignition

No 

Ignition

No

Ignition*

Relay No 

Ignition

No 

Ignition

No

Ignition*

Headlight filament Ignition No 

Ignition

No 

Ignition

PTC heater Ignition No 

Ignition Ignition*

Ignition Source Test

9/28/2011

*Based on previous 

testing at INERIS
14

Ignition Temperature with a hot surface

Summary....with oil

• AC5 and AC6 equivalent and not significantly different than without oil

• Higher ignition temperature for both AC5 & AC6 (+100°C) compared to R-1234yf

R-1234yf

AC5

AC6

0°C 750°C 850°C

9/28/2011
15

Flammability summary

 According to previous information, AC5 and AC6 

classification foreseen so far is as follows : 

USA EU

AC5/R-1234yf AC6 AC5/R-1234yf AC6

MAC system 

application A2L A2L A2L A2L

Transport & 

handling [MSDS] Flammable Nonflammable Flammable Nonflammable

Service tbc tbc tbc tbc

Building codes Flammable Still under 

review Flammable Still under review

9/28/2011
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Refrigerant Thermal Decomposition

 When exposed to sufficient energy sources all 

fluorinated refrigerants may decompose to produce 

HF

 The amount of HF generated depends on the concentration of fluorinated 

refrigerant in contact with energy source, size and shape of energy source, 

and time of contact

 Testing of HF generation conducted with an actual 

vehicle (Hughes Associates) and in bench 

experiments (INERIS)

 INERIS results indicate the HF generated due to 

thermal decomposition is the same order of 

magnitude for AC5/AC6/R-1234yf

9/28/2011
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Vehicle HF Concentrations Produced 

by Thermal Decomposition 

 Concentration of HF at the breath level in the 

Interior of the Vehicle are considered in the risk 

assessment

 Hot Body near air inlet (700oC peak temperature)

 Represents extreme engine operation 

 Hood seal removed allowing direct path to cabin air 

intake, secondary failure

 Blower on outside air, high speed

 AC6 and R-1234yf are similar in terms of HF 

produced by thermal decomposition

 AC5 seems to produce somewhat more HF than R1234yf 

 Correlation to results at INERIS is under review

9/28/2011
18 9/28/2011

Toxicology

 Provisional OELs have been 

assigned to AC5 and AC6 based on 

suite of test data

 Reviewed by Dr Lewandowski in CRP

 R-1234yf 500ppm

 AC5 800ppm

 AC6 900ppm

 R-134a 1000ppm

Science and Strategies for 

Safe Environments
19

Risk Assessment Methodology

 Structured approach carried out by same company as did 

CRP-1234 FTA following same basic methodology

 Potential scenarios and inputs considered by MRB CRP team

 Failure modes considered

 Collision, Equipment Failure, Corrosion, Vehicle Fires, Service and 

Repair

 Considered exposures to

 Refrigerant, Fire, Decomposition products

 Included Hybrid Vehicles and Vehicles with Dual Evaporator 

Systems

 Developed Fault Trees for AC5, AC6 and R-1234yf (due to updated 

inputs)

 Results for R-1234yf qualitatively similar to prior 

analysis (i.e., risks of all refrigerants are well below 

other commonly accepted risks)

9/28/2011
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Risk Assessment Results

Probabilities of Various Adverse events Compared to Probabilities of Events

Associated with Vehicle Operation-Related Refrigerant Leaks

Event Probability per vehicle 

per operating hour

Probability of being in a police reported vehicle collision1 5 x 10-5

Probability of dying during a 5000-mile plane trip2 4 x 10-7

Probability of vehicle collision due to vehicle brake failure3 3 x 10-7

Probability of highway vehicle fire (any cause)4 1 x 10-7

Probability of an airbag-related fatality associated with a vehicle collision5 2 x 10-10

Probability of vehicle occupant/former occupant experiencing HF exposure 

above health based limits associated with R-1234yf ignition/ decomposition. 6 x 10-14

Probability of vehicle occupant/former occupant experiencing HF exposure 

above health based limits associated with AC6 ignition/decomposition. 6 x 10-14

Probability of vehicle occupant being exposed to an open flame due to R1234yf ignition 9 x 10-15

Probability of vehicle occupant being exposed to an open flame due to AC6

ignition 7 x 10-17

Probability of AC service technician exposure to an open flame due to R1234yf ignition (per hour of vehicle service) 8 x 10-21

Probability of AC service technician exposure to an open flame due to AC6

ignition (per hour of vehicle service) 5 x 10-22

9/28/2011
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0

5

10

15

20

25

30

35

0 5 10 15 20 25

Vehicle Speed (Km/h)

Time (min)

Vehicle Cool-down Test Procedure

Ambient = 45°C

Humidity = 45%

Solar Load = 1000 W/m2

Re-Circulation

Idle
23

Cool-down Performance

R134a vs. AC6 [Drop-in Test]

0

10

20

30

40

50

60

0 5 10 15 20 25

Temp (

°C)

Time (min)

R-134a - Avg Vent R-134a - Avg Front Breath

AC6 - Avg Vent AC6 - Avg Front Breath
Seals AC5

Oil1

AC5

Oil2

AC6

Oil1

AC6

Oil2

EPDM std. Ѵ Ѵ Ѵ Ѵ

EPDM opt. Ѵ Ѵ Ѵ Ѵ

HNBR 1 Ѵ Ѵ Ѵ Ѵ

HNBR 2 Ѵ Ѵ Ѵ Ѵ

CR Ѵ Ѵ Ѵ Ѵ

Compatibility Seals 

Nearly all seal material show changes of their properties in tolerable 

dimension

Several slight effects with oil (observable about color and IR-spectra)

 No general problem with seal compatibility and AC5 / AC6
hose AC5

Oil1

AC6

Oil1

AC5

Oil2

AC6

Oil2

AC5

Oil3

AC6

Oil3

PA type

PA type -

PA type - - -

PA type

PA type

IIR type - - -

CR type - - -

BIIR type - - -

CR type - - -

Rubber

Compatibility AC hoses
Refrigerant Losses from hoses

Selective permeation Permeation rate @ 

90°C

hose AC5 AC6 AC5 AC6

Veneer Type

Veneer Type

Rubber Type

Barrier Type

Barrier Type

Veneer Type

Barrier Type -

Next Gen Veneer 

Next Gen Veneer -

Barrier - -

Next Gen Veneer

Veneer [Dev] 
Compilation stability, electrical properties, 

miscibility

Stability Electrical 

properties

Miscibility

AC5 AC6 AC5 & AC6 AC5 & AC6

Oil Type 1 - -

Oil Type 2 - -

Oil Type 3
28 9/28/2011

Service and handling

 AC5 and AC6 are zeotropic refrigerants

 Method of production and delivery into system of 

each refrigerant in-specification has been proven

 Handling effects on composition are understood

 Effect of composition on performance understood

 Work now underway on the effect on composition 

of practical recovery and reclaim techniques

 Refrigerant identifier technology being developed

 Proof of concept successful

 Work on field instrument in plan

 Further work planned to inform procedures for 

handling, recovery and recycle
29

SAE Standards Assessment

Standard Number/Title Action Plan

J639 Safety Standards for Motor Vehicle Refrigerant Vapor Compression Systems •New Fitting/Cautions on blend

J1658 Alternate Refrigerant Consistency Criteria for Use in Mobile Air-Conditioning 

Systems •Update and assign a new number

J2064 R-134a and R-1234yf Refrigerant Automotive Air-Conditioning Hose and 

Assemblies •No update needed right now

J2099 Standard of Purity for Recycled R-134a and R-1234yf or Use in Mobile Airconditioning Systems 

•Simply update to reference new 

refrigerant

J2297 ULTRAVIOLET LEAK DETECTION: STABILITY AND COMPATIBILITY CRITERIA OF 

FLUORESCENT REFRIGERANT LEAK DETECTION DYES FOR MOBILE R-R-134a and RR-1234yf (HFO-R-1234yf) AIR-CONDITIONING SYSTEMS

•Simply update to reference new 

refrigerant

J2670 Stability and Compatibility Criteria for Additives and Flushing Materials Intended 

for Use in R-R-134a and R-R-1234yf Vehicle Air-Conditioning Systems

•Simply update to reference new 

refrigerant

J2772 Measurement of Passenger Compartment Refrigerant Concentrations under 

system refrigerant leakage conditions 

•Simply update to reference new 

refrigerant

J2773 Standard for Refrigerant Risk Analysis for Mobile Air Conditioning Systems •Simply update to reference new 

refrigerant

J2842 R-1234yf and R744 Design Criteria and Certification for OEM Mobile Air 

Conditioning Evaporator and Service Replacements

•Simply update to reference new 

refrigerant

J2843 R-1234yf Recovery/Recycling/Recharging Equipment for Flammable Refrigerants 

for Mobile Air-Conditioning Systems •New standard under development

J2844 R-1234yf New Refrigerant Purity and Container Requirements Used in Mobile AirConditioning Systems •New standard under development

J2845 Technician Training for Safe Service and Containment of Refrigerants Used in 

Mobile A/C Systems (R-744, and R-1234yf) •New standard under development

J2851 R-1234yf Refrigerant Recovery Equipment for Mobile Automotive Air-Conditioning 

Systems •New standard under development

J2888 R-1234yf Service Hose, Fittings and Couplers for Mobile Refrigerant Systems 

Service Equipment 

•Simply update to reference new 

refrigerant

J2911 Certification Requirements For Mobile Air Conditioning System Components, 

Service Equipment, and Service Technicians to Meet SAE J Standards 

•Simply update to reference new 

refrigerant

J2912 R-1234yf Refrigerant Identification Equipment for Use with Mobile Air Conditioning 

Systems •New standard under development

9/28/2011
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Work Plan to Finish

 Work to reach decision point on key open issues

 Service & handling

 Estimate 3-4 months to prove technique for workshop recovery 

and re-use

 Performance optimisation

 Development of optimal evaporator configuration

 Material/Oil optimisation

 Durability testing for compressor

 Final safety studies

 Consider AC6 potential in a heat pump system

 Goal to finish technical work no later than mid 2012

 Non-Technical issues are not addressed inside the CRP

 SNAP submission with CRP support

 Engagement of new team members are welcomed

 Meeting open for potential new OEM sponsors to be held on 

Thursday afternoon

9/28/2011
31

Conclusions

 AC5 and AC6 have been extensively tested via a rigorous CRP

 AC5 matches the LCCP performance of R-1234yf 

 AC6 needs some further improvement in energy efficiency 

 Reduced flammability of AC6 offers potential benefits; AC5 is 

comparable to R-1234yf in terms of flammability

 Systems components, lubricants and hoses are available for 

AC5 and AC6 systems

 Project has made remarkable progress in 7 months; some 

further work still to complete in order to allow final selection 

of technically preferred fluid

 Compatibility with electrical compressors provide an 

opportunity for these fluids for use with heat pump systems in 

electric vehicles

9/28/2011

Either AC5 or AC6 offer options as low GWP refrigerants for 

MAC systems
32

MRB CRP Sponsors

9/28/2011