UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	1

A2/A3 Refrigerants in HVAC Products

UL JTG WG1

This report is being issued by UL JTG WG1 (HVAC) to the UL JTG Executive Committee as 

recommendations relative to use of A2/A3 refrigerants in HVAC products covered by UL standards. 

The UL JTG WG1 is tasked with making recommendation for use of A2/A3 refrigerants in HVAC 

products covered by related UL standards. Specifically: UL 60335-2-40, UL 484, and UL 474.

(*) The WG can only propose changes and assist in drafting revisions in the standards. 

Ultimately the standards must be revised by UL through the UL STP process.

Scope of Work – WG1 HVAC

The scope of work is limited to safety requirements for use of A2 and A3 refrigerants with in 

the products covered by UL 60335-2-40, UL 484, and U L474.

Requirements for A2L refrigerants in these standards will be addressed after IEC 

TC61/SC61D/WG9 completes their work. This work may start once WG9 reaches the CDV 

stage and the standards changes are reaching conclusion.

UL 484 Scope: (Generally free discharge, but may be ducted)

 Room Air-Conditioners (fixed appliance)

 PTAC (Packaged Terminal Air-Conditioners) – (fixed appliance)

 “Special purpose air-conditioners”

o Spot Coolers (portable)

o Computer Room units (portable if with wheels)

o Enclosure Air-Conditioner – (data centers – fixed appliance)

 Recreational vehicle air-conditioners (fixed appliance)

 One on One mini-split. (non-ducted) 

UL 474 Scope:

 Dehumidifiers.

UL 60335-2-40

 Most air-conditioning products under 600v not covered by UL484 and UL474 are 

covered under UL60335-2-40. Most over 600v products are covered by UL1995.

This report is structured in two sections. The first section will specifically address UL 484. The 

second section will address UL 60335-2-40 and U L474 (dehumidifiers). 
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	2

Executive Summary

WG1 recommends that the use of A2/A3 flammable refrigerants in HVAC products covered by 

UL60335-2-40, UL484, and UL474 should be limited by the following constraints:

1. Refrigerant charge for any single refrigeration system shall not exceed; 

m1 (kg) = 3m3* LFL

2. Refrigeration systems shall be limited to factory sealed appliances systems which are 

charged in the factory. Note: factory sealed does not allow service valves for routine 

service. 

3. If ducted, potential ignition sources shall not be installed in the duct.

4. The temperature of surfaces which may be exposed to leaking refrigerant shall be 

limited to the refrigerant Auto Ignition Temperature (AIT) minus 100K.

Note: Additional markings and instructions shall be provided. These are detailed in marked 

up copies of UL484 SA and UL60335-2-40 and are available on request.

UL484 – “Room Air Conditioners” – Report Section 1

Introduction

UL 484 and IEC 60335-2-40 currently contain requirements for flammable refrigerant charge 

limits based on m1 and m2 calculated based on the refrigerant LFL. The m1 charge limit is based 

on unrestricted installation; while m2 charge limit is based on restrictions on room size. The 

charge limit for charge levels m1 <M< m2, the maximum charge is based on the room area in an 

unventilated space (no mechanical or natural ventilation), making installed room area critical to 

safety for charges greater than m1. 

With the introduction of flammable refrigerants to the domestic residential and light 

commercial market place we must recognize the impact on the consumer, users, installers, 

inspectors, service personnel, and customers in retail establishments relative to the products 

being addressed. 

Because of a number of factors the committee recommends limiting the charge to m1 for 

domestic residential and light commercial application, including recreation vehicles. 

The factors considered were: 

1. With regards to the consumer, the North American consumer market is transitioning

from an environment with A1 non-flammable refrigerants to low GWP alternatives

which may be flammable. With non-flammable refrigerants it has not been necessary to 

consider the installed room area in the determination of safety requirements. With 
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	3

flammable refrigerants, a number of additional mitigation steps, including considering 

the installed area, will need to be considered for safety depending on the charge level. 

2. Consumer purchasing today is based on cooling needs and affordability without giving 

consideration of room size for refrigerant safety. It is common knowledge and welldocumented that some consumers, due to their perceived understanding of the

products, will install these products without consideration of the instructions and 

related safety documents. It is expected that these practices will not change due to the 

use of flammable refrigerants.

3. These products are considered appliances and are not controlled by building codes, are 

not subject to inspection, and are generally not installed by licensed HVAC technicians.

4. Service personnel today are accustomed to working with non-flammable A1 

refrigerants. With flammable refrigerants additional precautions and training are 

required when installing and servicing.

5. In the U.S. it is the common practice in northern regions to remove the room air 

conditioner from the window during the colder seasons. Installing and removing a room

air conditioner from a window each season increases the chance that the room air 

conditioner will be damaged such that leakage of the refrigerant could occur.

6. With the seasonal removal, a room air conditioner may be stored in a small room or 

closet, which may include ignition sources such as gas hot water heaters. Although the 

room air conditioners are not operational during storage, the possibility for leakage still 

exists. Such leakage within the small room or closet increases the risk of ignition based 

on the small room size.

7. Portable air conditioners are, by design, intended to be frequently moved from room to 

room on demand by the user. Like window room air conditioners, they are also likely to 

be stored off-season in small rooms or closets.

Therefore, the JTG/WG1 determined that safety must be controlled by charge limit and 

cannot be based on installed room size and the expectation that minimum room areas 

requirements will always be complied with. For this reason refrigerant charge amounts 

greater than m1 should not be allowed.

In addition, consideration must be given to the charge level limits for m1, in consideration of

common installation practices and home construction, including room sizes relative to the airconditioner. 
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	4

Previous work done by IEC TC61/SC61C1concentrated on appropriate charge limits for 

refrigerators. For determination of m1 in refrigerators a volume of 8 m3(2m by 2m by 2m) as a 

“small” kitchen area and a 50% safety factor (50% LFL kg/m3) was used for determining charge 

quantity limits:

m1 = 8m3x 50% x LFL = 4m3x LFL

Ref: 8m3= 2m x 2m x 2m (6.6’ x 6.6’ x 6.6’)

(*) This equation yields 152 grams of R290 (propane). IEC TC61/SC61C (IEC 60335-2-24 and 60335-

2-89) rounded to 150 g. 

Note 1: This approach does not take into account pooling or stratification of heavier 

than air refrigerants. However, this approach for determination of m1 limits has been 

globally accepted.

This equation was also accepted for determination of the m1 limits for HVAC products in IEC 

60335-2-40 and ISO 5149; and is currently published in the Supplemental Annex to UL 484.

WG1 considered that room air conditioners are known to be installed and stored in smaller 

spaces than refrigerators and therefore a smaller volume should be used in the 

determination of m1.

It is common in the USA to find these products installed in rooms that are smaller than 8m3. 

Some examples are:

 Airport parking garage attendant booth.

 Toll booths

 Drive through coffee stations

 Portable lunch canteens

 Recreation vehicles.

The committee estimated the typical size of these applications may be as small as 4’ x 8’ x 6.6’ 

or 5.94 m3. This was then rounded to 6 m3. 

Therefore, it is recommended that the determination of m1 for products in UL 484 be based on

a volume of 6 m3(1.7m by 1.7m by 2m) as a “small” room, and using the same 50% safety 

factor (50%LFL kg/m3) for determining charge quantity limits. The equation then becomes;

m1 = 6m3x 50% x LFL 

 

1

Supporting information from TC61/SC61C records and unpublished documents were researched to validate the 

8m3basis.
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	5

m1 = 3m3x LFL

Ref: 6m3= 1.73m x 1.73m x 2m (5.7’ x 5.7’ x 6.6’)

Based on this equation the charge limits for select refrigerants are: 

Table 1

(*) Charge limits apply to the largest single refrigeration circuit in the appliance.

As a check on the impact of our assumption on room size (6m3), the committee evaluated

extreme cases of storage or operation in even smaller rooms. Utilizing this equation, the 

average concentration could potentially reach the following levels;

 At a room volume of 4 m3the average concentration could reach 75% of the LFL

(*) 4m3= 1.4m x 1.4m x 2m (4.6’x4.6’x6.6’)

 At a room volume of 3 m3, the average concentration could reach 100% of the LFL

(*) 3m

3

= 1.2 x 1.2m x 2m (4’x4’x6.6’)

Although these products may be stored in such small rooms, with the m1 charge, the potential

for a catastrophic leak reaching the LFL and a concurrent presence of an ignition source is 

unlikely.

As a reference, global experiential evidence is largely around 100g of A3 refrigerant (R290 or

R600a) used in household refrigerators designed for flammable refrigerants is an accepted level 

of safety. Although the use of refrigerators with flammable refrigerant in the USA is very small, 

this is not the case in Europe and Asia. In these regions, refrigerators designed specifically for

flammable refrigerants have been in the market place for over 15 years and over 100,000,000 

household refrigerators using flammable refrigerants are in use with low level of incidents.

Published standards, IEC 60335-2-40 and ISO 5149 currently set charge limits of:

 m1 = 4 m

3

*LFL (no area requirements)

 m2 = 26 m

3

*LFL (with requirements for minimum area) 

However, for direct release air-conditioning products, no evidence could be identified of 

significant production of these products at charge levels greater than 100g of A3, with the 

A3 R290 6.0 0.038 0.114 45 46.3 5.28 0.25

A3 R441A 6.0 0.034 0.102 45 46.1 4.70 0.25

A2 R152a 6.0 0.130 0.390 23 16.3 6.36 0.38

A2L R32 6.0 0.306 0.918 6.7 9.55 8.77 30.00

Reference

heat 

release 

(MJ)

MIE 

(mJ)

HOC 

Refrig (MJ/kg)

Room 

Volume

(m3)

LFL 

(kg/m3) m1 (kg)

BV 

(cm/s)
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	6

exception of Portable Air Conditioners. There are other products, such as EAHP (Exhaust Air 

Heat Pumps) which have up to 500g of R290 on the market, but these are indirect release 

systems.

Portable Air Conditioners with up to 300g of R290 have been in production for many years in 

the global market place. The team looked for documented evidence of failures, however, could 

not find any formal mandatory reporting of fires and similar incidences that could be 

referenced. In the USA we would reference CPSC, NFPA, and similar sources. In other countries, 

detailed fire incident reporting and collection of this data is not available to the same extent.

The UL JTG WG1 committee, at this time, is not considering differing values for maximum 

charge quantities for fixed appliances or stationary appliances within the scope of UL 484. The 

committee fully recognizes that the maximum charges discussed in the portable appliance

discussion above does not consider; a) potential mitigation factors that are more applicable for 

fixed or stationary appliances, b) the likely larger room volumes of those products, nor c) the 

extended flammable refrigerant properties and characteristics discussed in the “Future 

Considerations” section of this report. As such, in the future the committee is open to

considering a modification of the maximum charge quantities for fixed or stationary appliances

given more analysis of such mitigation factors and applied room volumes.

Impact

Estimated average product capacity, based on proposed charge limits, for select refrigerants 

are;

Table 2

Assumptions-> 

(*) Estimated capacity limits are based on a single refrigeration circuit in the appliance.

Notes: 

1. The estimated average product capacity has been calculated on typical lbm/ton charge 

levels. Actual lbm/ton charge will vary considerably with product design and 

technology.

2. Technology exists to reduce the lbm/ton, such as micro-channel heat exchangers. 

3. The capacity limit estimates are based on products with a single refrigeration system. 

Dual systems would double the estimated capacity.

Type R290 R152a R32

Window 5,000 6,600 25,300

PTAC 3,200 4,200 16,000

Portable 5,000 6,600 25,300

Btuh (max)

Equiv % 50% 130% 80%

R410a R290 R152a R32

Window 1.20 0.60 1.56 0.96

PTAC 1.90 0.95 2.47 1.52

Portable 1.20 0.60 1.56 0.96

lbm/ton
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	7

Additional Requirements

1. It is recommended that use of A2/A3 refrigerants be further limited to:

• Factory charged

• Factory sealed systems (service ports for routine service and maintenance are not 

allowed)

The critical to safety factor in these products is the charge level. By limiting the use to 

factory charged, factory sealed appliances it places a much higher level of control on the 

installed charge and includes a factory leak test of the complete sealed system. As such,

the critical to safety factor in these products - charge level - is tightly controlled.

Risk assessments2for flammable refrigerants consistently identify servicing of the 

refrigeration systems as the highest risk activity. Limiting the use of A2/A3 to factory 

sealed systems reduces the probability of a service related events. It also increases the 

probability that if the refrigeration system is serviced, that it will be by qualified service 

personnel in a controlled environment. 

2. Products such as PTAC’s and A/C for recreational vehicles may include short ducts. For 

ducted applications, the ducts shall not contain ignition sources.

3. For products using flammable refrigerants, any surface temperature which may be 

exposed to leaked refrigerant (including auxiliary electric or fossil fuel heat) shall be

limited to the refrigerant Auto Ignition Temperature (AIT) less 100K. This applies to 

normal operation – not abnormal test conditions. (reference UL 484 SA 5.3.1) 

 

2

Risk Assessment of HFC-32 and HFC-32/134a (30/70 wt. %) in Split System Residential Heat Pumps, April, 1998, 

prepared by; William Goetzler, Lisa Bendixen, Paula Bartholomew - Arthur D. Little, Inc., 20 Acorn Park, Cambridge, 

MA 02140 USA
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	8

UL 60335-2-40 – Report Section 2

JTG WG1 recommends that for the next revision of UL 60335-2-40 include the following 

revisions relative to A2/A3 flammable refrigerants.

 Include the requirements for products covered by UL484 Room Air-Conditioners

 Include the requirements for products covered by UL474 Dehumidifiers.

 And similar products covered by UL60335-2-40 to the extent that they comply with the 

same requirements and limitations – for example heat pump water heaters. 

The A2/A3 refrigerant safety requirements will be written to allow use of A2/A3 refrigerants in 

any factory sealed factory charged appliance. Charge levels will be limited to m1 = 3 x LFL. 

Charge levels greater than m1 will not be allowed. These restrictions apply to direct release 

systems only.

These same requirements apply to dehumidifiers. Flammable refrigerants are currently not 

allowed for use in dehumidifiers (UL 474). Adding the above requirements to UL 60335-2-40, 

will now allow use of A2/A3 refrigerants in dehumidifiers up to m1 = 3 m

3

x LFL (114g R290). 

The highest sales volume of products in the market, generally have charge levels under 120g of 

410A (equivalent to ~60g ofR290). The largest residential dehumidifier that UL has listed is has 

305g R410A (equivalent to ~ 150g of R290)

(*) It should be noted that UL has received no requests to add requirements for A2/A3 

refrigerants in dehumidifiers at this time. 

Requirements for A2L refrigerants in these standards will be addressed after IEC 

TC61/SC61D/WG9 completes their work. This work may start once WG9 reaches the CDV stage 

and the standards changes are reaching conclusion.

JTG WG1 will work to mark up UL60335-2-40 1st Edition (based on IEC 60335-2-40 4.2 Edition)

with these changes and provide to CANENA WG2. CANENA WG2 will update UL60335-2-40 1

st

Edition to harmonize with the IEC 60335-2-40 5th Edition, and IEC 60335-1 5th Edition to the 

greatest extent possible. 

It should be noted that UL60335-2-40 is a tri-national harmonized standard. CANENA WG2 

includes representation from USA, Mexico, and Canada with a goal of North American 

harmonization. 

Ultimately, all revisions to UL60335-2-40 are subject to approval by the UL STP.
UL JTG WG1 – A2/A3 Report to Executive Committee

UL	JTG	WG1 – May	20,	2014 Page	9

Future Considerations

A2/A3 refrigerants by definition are flammable and can produce deflagrations. Like all 

flammable products, combustion involves direct and indirect heating of surroundings, 

consumption of oxygen and a pressure wave on ignition. ASHRAE and ISO have placed these 

flammable refrigerants into class by flammability properties and these classes show significant 

differences in their hazard potential. At this point in our analysis all flammable refrigerants

have been treated without consideration of these differences. This analysis sets the volume of 

flammable gas equal regardless of flammability classification.

We have not accounted for differences in flame properties, such as;

 slower burning velocity ( slower kinetics)

 higher MIEs

 unstable flames (self-destructive rather than self-propagating)

 large quenching distance

 Incomplete combustion

 lower severity and explosion damage

 lower overpressure with minimal venting

 increased flame thickness. Time scale of reaction closer to time scale of heat and mass 

transfer

 lower (dp/dt)max (pressure rise)

As such, this approach is conservative and there may be room for additional discussion in the 

future with further considerations of available research and information.