U.S. EPA 

March 4, 2014

Nanette Lockwood – Climate Policy

Nanette.lockwood@irco.com (980) 228-1532

Steve Kujak – Refrigerant Technology

Skujak@trane.com (608) 787-3766

Bill Hansen – Unitary Product Development (via phone)

Bill.hansen@trane.com (608) 787-2488

Ken Schultz – Thermal Systems

Kschultz@trane.com (608) 787-3735
Refrigerant Flammability and the 

Standards

Steve Kujak

IR Refrigerants Technology Leader
3

Recap - What is Flammable?

Measurement of burning velocity and heat of combustion do 

not indicate the risk and severity of an event
4

Relative Flammability Examples

Some Class 2 refrigerants can look like Class 3’s

Noticeable differences in 2L’s

Class 3 

Propane

Class 2 

R152a

Class 2L

<10 to 6.7 cm/sec

R143a

R32

Ammonia

Class 2L

<5 cm/sec

60% R32/40% R134a

Propane pool 120 

grams R152a 300 grams 

Pool

R152a bunsen 

burner

R143a bunsen 

burner

R32 1000 gram 

Pool

70_30 R32R134a 

Bunsen Burner

 Pool 60_40 Blend 

R32R134a Pilot
5

Recap-Preventing Ignition Events

Simulations show flammable mixtures are possible in 

occupied spaces with a potential for ignition events

Concentration between LFL-UFL

Ignition Source Air Velocity less than 

Burning Velocity

Ignition Event

Controls

• Restrict charge size

• Redesign system to put charge outside

• Detection & ventilation

Controls

• Can only control within equipment

• Control ignition sources outside equipment ($$$$)

• Allow only high MIE’s (minimum ignition energy) 

refrigerants

Controls

Turn on fan 

(not realistic from a power use 

and equip storage standpoint)

Could feed the flames!

(Strong to weak)

1. Flames

2. Electrical

3. Hot surfaces
6

Standards- Flammability Focus

Safety standards developing on multiple fronts

• Restrict charge size

• Redesign system to put charge outside

• Detection & ventilation

• Put sources/refrigerant within equipment

• Control ignition sources outside equipment ($$$$)

• Allow only high MIE’s (minimum ignition energy) 

refrigerants

Putting controls in place within and some controls for outside equipment;

1. Flames

2. Electrical

3. Hot surfaces

Controlling Concentration 

between LFL and UFL

Controlling Ignition Sources

Ignition 

Event
7

R1234ze = no ignition at room temp, No BV

R1234yf = 5,000 mj (BV = 1.5 cm/sec))

R717 ~<100 mj (BV=7.2 cm/sec)

R32 ~<30 mj (BV = 6.7 cm/sec)

R446A~<10 mj (BV = 9.0 cm/sec)

R152a ~<0.38 mj (BV = 23 cm/sec)

R290 ~<0.25 mj (BV = 40 cm/sec) 

Recap-Minimum Ignition Source Strength 

Comparison

ASHRAE proposal 

• 5 cm/sec 2L limit 

• Based on ASHRAE 1584 work

• Eliminates human static 

discharge possibility

• Ignition source up to 100 mj

• Status: Voted to further review

Burning Velocity vs. Minimum Ignition Energy (MIE) 

ASHRAE TRP-1584

Flammable

Region Non-Flammable

Region

100x change in MIE 

over 7 cm/s range

Proposed 2L Limit  5 cm/sec

Human static 

discharge

Not all current ASHRAE 2Ls are likely to remain 2L

Class 3

Class 2

Class 2L, BV 10 to 5 cm/sec

Class 2L, BV <5 cm/sec
Bill Hansen

Director Unitary New Product Development

Managing Flammability in the Standards
9

UL 484 Products are Installed 

in Existing Homes and Businesses

Window and Floor Mounted Products have the 

Greatest Risk for Flammability

- Room Air-Conditioners

- Portables

- PTAC’s (largest charges typically)

Common Ignition Sources cannot be regulated 

1. Flames

2. Electrical

3. Hot surfaces

UL 484 Can Only Regulate the Product, NOT the Application

Consumer Purchase and 

Applied
10

Charge Size Methodology

and Application Limits 

Charges sizes

- These products are historically hermetic products with small refrigerant charges

- Used Equiv. 1.0 lbm/ton R410A

Cooling loads by application type

Highest demand to lowest (ft2/ton cooling)

1. Commercial Kitchen - 93

2. Restaurant – 187

3. Retail – 393 

4. Residential – 850

Leak rate scenarios 

- Fast Leak – 25%/min

Flow Model

- Quadratic – Inherent flammable flow 

region 

Application Height

- Can lead to unsafe situations
11

Charge Size Methodology – Equation 

Flammability equation has some gaps for safety and does not apply to all 

product application situations. 

Charge calculation heavily dependent on;

-LFL of refrigerant

-Charge per ton capacity varies

-Application height

-Building cooling load demand

-Safety factor constant of 2.5

AL (Application Limit) = Amin (m2)/Capclg (m2) = 1.0 or Amin (m2) - Capclg (m2) = 0

Where:

Amin = (M/(2.5*(LFL)5/4*h0))2 = (m2)

 M – mass of the largest refrigerant system (kg)

 LFL – lower flammability limit (kg/m3)

 h0 – point of release of leaked refrigerant (m)

o Ceiling mounted – 2.2m

o Wall mounted – 1.8m

o Window mounted – 1.0m

o Floor mounted – 0.6m

Capclg = M/m'*Ac = (m2)

 M – mass of the largest refrigerant system (kg)

 m' – mass refrigerant/cooling capacity (kg/kW)

 Ac – Area cooled/kw cooling capacity (m2/kW)

• AL - When the area that can be cooled is less than the area required for 

safety there is a high risk of mis-application 

• Floor Mounted, Commercial Kitchens is worst case.

• Can only be controlled by charge limits
12

Class 3 – Max Charge Size

Current EPA Rule 17 safe level for Class 3 

Limits flammability risks

Class 3 Application Limits (kg)

• Floor < 57g (0.016)

• Window < 57g (0.045)

• Wall 0.145

• Ceiling 0.217

*UL 484 1 Kg limit unjustified

*UL484 limit should based on 

household refrigerators (UL250)

Initial Proposed UL

Limit - 1 kg 

“Limit unsafe”

R290 ~<0.25 mj (BV = 40 cm/sec) 
13

Class 2 - Max Charge Sizes

R-152a Application Limits (kg)

• Floor 0.132

• Window 0.378

• Wall 1.19

• Ceiling 1.78

*Limits ~4x to 8x higher than 

Class 3 based on LFL’s being 

higher.

*Class 2 MIE’s and BV’s very

similar to hydrocarbons. Should 

they be treated like Class 3?

R152a ~<0.38 mj (BV = 23 cm/sec)

R290 ~<0.25 mj (BV = 40 cm/sec) 

Current EPA Rule 17 safe level for all Class 2 at this point

Limits flammability risks

Initial Proposed UL Limit

2.8 kg R152a 

8 kg R32

“Limits Unsafe”
14

Class 2L’s Charge Sizes

Safety Methodology Breaks Down

LFL and BV appear insufficient to set 2L charge limits

Industry working to resolve

*Charge limits 3x-19x more than Class 2 R152a.

*R1234yf less safe than R-32? 

*R1234ze would be less safe than R32 as well? Does 

that make sense?

*Should a max charge limit be set for this 2L category?

*Should a new flammability class be developed?

Floor Window Wall Ceiling

Area - m

2

0.4 1.1 3.7 5.5

Charge - kg 0.016 0.045 0.145 0.217

Area - m

2

1.9 5.4 17.5 26.1

Charge - kg 0.132 0.37 1.2 1.8

Area - m

2

8 22 71 106

Charge - kg 0.41 1.1 3.7 5.5

Area - m

2

52 145 471 704

Charge - kg 2.5 6.9 22.2 33.2

Area - m

2

22 61 197 295

Charge - kg 1.5 4.2 13.5 20.1

Note 1 - The value is the % charge (lbm/ton) required for the refrigerant relative to R410a.

R1234yf

R446A

40 0.25

6.7 30

0.156

 Application Limits

R290

R32 

R152a

Area/

Charge

Equiv 

R410a 1

75%

130%

100%

Refrig

Class

BV

 cm/s

MIE

<Mj

LFL

kg/m

3

0.306

0.290 130%

A3

A2

A2L

A2L

A2L 1.5 5000

90%

23 0.38

9 10

0.038

0.110

Current Committee Discussions
15

Conclusions

• We do not recommend adopting UL 484 until it is completely revised

- Class 3 will have << 1 Kg charge limits 

 Industry believes 1 Kg creates unsafe conditions for highly flammable refrigerants

 ISO 5149 includes 1kg and higher charge limits 

- Competitive pressures and not justified through science

- Adoption potential will be driven by competitor interests and local pressures

- Class 2 will also have lower charge limits

- Timing

 Meeting at UL Northbrook Mar 4th to continue to revise draft

 Target complete draft June 2014

 Review complete 4Q14

 Implementation early 2015

- No 2L updates in this revision

 Expect 2L UL revisions to follow IEC 2-40 acceptance (2017)

• UL484 charge limits should not substantially exceed EPA Rule 17 

charge limits for Class 2 & 3 refrigerants

- The science supports a charge limit restriction “on the small side” 

for self contained products with flammable refrigerants
Low GWP Replacements for R410A & R22

Ken Schultz, PhD 

Staff Thermal Systems Engineer
17

The Transition Away from R22

 Came down to three alternatives globally...

oEarly adoption in Europe = R404A

oNear drop-in replacement = R407C

oHigher pressure/capacity = R410A

And the winner is ... R410A.

modeled conditions 

approximate

AHRI Std-210/240 

Condition A

Tevap = 50°F

Tcond = 115°F
18

Transition Away from R410A

 Primary constituents in blends

o R32 GWP = 675 class = A2L

o R1234yf 4 A2L

o R1234ze 6 A2L

 Secondary constituents in blends

o R125, R134a, R152a, CO2

The new “HFO’s”. “Mildly” flammable.

Lacking non-flammable low GWP blend materials (R-125-like).

Industry needs to find more high pressure chemistries.

Will McLinden and Domanski find anything? 

What’s in the toolbox?

o NO very low GWP (<150) refrigerant 

molecules with pressures comparable 

to R410A or R22 (that aren’t A3’s).

o R32 needed to keep pressures (ie, 

capacities) in the range of R410A or 

R22.
19

Transition Away from R410A

 R32 and blends proposed under 

AHRI Low GWP AREP I ...

And the winner will be ... ???.

 R410A No	A1’s!

 R22/R407C
20

R410A/R22 Alt’s Tested by Trane

 R410A-like blends 

have GWPs of ~500. A1 1295

A2L 206

A2L 407

A2L 979

A1 1577

A2L 482

A2L 331

A2L 494

A2L 494

A2L 246

A2L 296

A2L 490

A2L 675

A1 2088

 R22-like blends 

have GWPs as 

low as 200-250.

A range of options.

A range of trade-off’s.
21

Best R410A Alt’s – Capacity & COP

 R32 (GWP = 675) o CAP and COP increased, but 

not as much as predicted.

 DR5 (GWP = 490) o Very similar performance to 

R410A; potential near drop-in

 L41’s(GWP = 494) o Small reductions in capacity; 

maybe okay?

 DR4 (296), ARM70a (482) o Performed better than 

expected – interesting?

measured results simple model measured results simple model

capacity efficiency

Need also to consider 

discharge temp’s, glide, 

HXer performance, ...
22

Best R22 Alt’s – Capacity & COP

 L20 (A2L, GWP = 330) o Matched predictions. Close 

match to R22 capacity; need 

to make up for lower 

efficiency.

 LTR4X (A1, GWP = 1300) o Matches R22 capacity, but 

efficiency is down. A1 but 

“high” GWP (~1300).

 DR7(A2L, 245), ARM32a(A1, 1575) o A little extra capacity, but 

efficiency is down ~10%.

measured results simple model measured results simple model

capacity efficiency

Need also to consider 

discharge temp’s, glide, 

HXer performance, ...
23

Compressor Discharge Temperature

Excessive discharge temperature creates reliability problems 

without mitigation (e.g., liquid or gas injection) 

Mitigation technologies impact performance

R410A alternatives R22 alternatives

R32 is 

worst 

offender!

Industry Limit
24

 Glide generally increases as move from R410A-like blends 

toward R22-like blends. 

o Capacity is generally decreasing in this direction. 

o GWP is generally decreasing in this direction. 

o Potential efficiency tends to increase in this direction. 

Temperature Glide in Zeotropic Blends

An ideal candidate has <2F of glide

Large glides because 

these blends contain CO2.
25

Comparison of Lower GWP Alternatives

†  reference R410A R32 DR5 L41’s .... DR7 L20 R22

CAP 1.00† +12% +1% -5% ? -25% -28% -29%

COP 1.00† +4% +3% +4% ? +2% +9% +11%

∆Tdchrg (°Fd) 0† +40 +15 +20 ? –10 +10 +5

Glide (°Fd) ~0 0 2 ~5 ? ~8 ~11 0

Hi Tamb 50C

CAP/COP

1.00

1.00

+7%

+6%

+6%

+5%

+4%

+3% ?

+1%

+0%

+7%

+6%

+8%

+8%

GWP 2088 675 490 494 ? 246 331 1810

Flam

BV (cm/s) A1 A2L~7

A2L

~4

A2L

~4 or ~9 ?

A2L

<3

A2L

6-7

A1

There are no ideal replacements for R410A or R22. 

What will make the best compromise? DR5? 
26

 “Toolbox” for R410A/R22 replacements is limited: 

o Blends of R32, R1234yf, and R1234ze with a sprinkling of others.

o R410A-like alternates are at best “2L”.

o R22-like alternates can be lowest GWP (330 .. 250).

 Large number of competing/opposing factors:

o thermodynamics

~ operating pressure = capacity

~ inherent efficiency 

~ blends = temperature glide

o range of operation  reliability

~ high ambient temperatures

~ compressor discharge temperatures

o safety and environment  flammability and GWP

Conclusions

CAP COP glide GWP

relationship trends

Lower GWP R410A & R-22 alternatives possible, 

however, with more compromises than today.
R410A & R22 Refrigerant Choices for High 

Ambient Temperatures

Ken Schultz, PhD 

Staff Thermal Systems Engineer
28

R22 to R410A Transition

 Did we give away 

performance at 

high ambient 

temperatures?

Walid Chakroun, Kuwait University

“Challenges For High Ambient Temperature Countries”

Seminar 18 @ ASHRAE/NYC Jan-2014

70

80

90

100

110

CA AZ NV UT TX CO FL MO VA NY WI

US 1% Cooling DB (°F)

In many locations, the design cooling loads occur at 

temperatures well above typical rating conditions (95°F/35°C)

Saudi Arabia 1% DB:

86.5°F .. 111.5°F

Kuwait max Tamb

= 52°C = 126°F

40.. 46.3°C 

104..115°F

India 1% Cooling DB: 

91°F .. 109°F
29

Performance - R410A Alternatives

R410A alternatives along with R22 for reference (modeled)

R-22 performance best at high ambients, but R410A 

and proposed alternatives are within 10%.
30

Performance - R-22 Alternatives

R-22 performance best at high ambients. 

L-20 looks like a good match but has high glide.

R22 alternatives along with R410A for reference (modeled)
31

Comparison of Test & Field Experiences

Measured: Koolman air-cooled water chiller (~4.5 RT)

Out test data is consistent with trends reported recently by 

Chakroun at ASHRAE/NY Conference (Jan-2014).
32

 R410A a good replacement for R22 in high ambients

o Loss of capacity (<10%) is manageable.

o Recently reported high ambient field experiences from Middle East 

validates R410A performance acceptable compared to R-22.

 Lower GWP alternative performance no worse than R410A

o Concerns/compromises

~ Compressor discharge temperatures a concern with most candidates.

~ Glide is also a concern with some R410A and with all R-22 candidates.

~ Safety – Some candidates have high burning velocities.

Conclusions

Lower GWP alternatives to R410A are possible, 

but there are more compromises.