Safety concerns for A2L
refrigerants in AC service
procedures“Alternative Refrigerants for High-Ambient Countries;
Risk Assessment of Future Refrigerants in Production,Installation, and Service”
28 October 2014
Dubai
Osami Kataoka
Senior Manager
On behalf of The Japan Refrigeration and Air
Conditioning Industry (JRAIA)

2Disclaimer• This presentation has been made based on thelatest technical information as accurate aspossible.
• However, the accuracy of the information shall not
be guaranteed, and related academia, JRAIA,
and/or its member companies shall bear no
responsibilities whatever for any damage that may
be caused as a result of using information anddocuments contained in this presentation.
• Usage of the information shall be made on users’
own responsibility.

3Contents
1. Introduction
2. Risk Assessment of JRAIA for A2L
refrigerants and statistics
3. A2L Flammability and service concern
a. Practical combustion including brazingb. Minimum Ignition Energyc. Flammable cloud
4. Overall Relative Risk
5. Other issues than flammability
6. Conclusion

4

1. Introduction• JRAIA is the HVAC&R industry association basicallyconsists of equipment manufacturers in Japan.
• Full members are 75 and associate members are 47
including major players of; Daikin, Fujitsu-General, Hitachi, Mitsubishi Electric,
Mitsubishi Heavy Industry, Panasonic, ToshibaCarrier• Mission of JRAIA are;
 Promotion and Improvement of the HVAC&R
Industry, Products and Components• Japanese market in is around 8.5 million residential
AC/HP and 0.8 million commercial AC/HP per year.

52.1 JRAIA Risk assessment• Joint projects of Japanese academia and industry for
A2L refrigerants are ongoing.
• The progress report of the projects can be found in
http://www.jsrae.or.jp/jsrae/committee/binensei/risk_e.html• Pretty much important information can be found.
• Presentations of the projects will be made at JRAIA
Symposium in Kobe on November 20 - 21, 2014 at
International Conference Center Kobe. Key results ofthe projects will be presented. Details of the event are;http://www.jraia.or.jp/symposium/index.html• In Japan, a few to several millions of residential minisplits have been sold with R32, but no accident has
been reported.

62.2 Service procedure and risk
• The risk assessment indicates relatively high risk inservice, installation, disposal, and use of outdoor unit.
• Key concern in service procedures are;– Accidental release and existing ignition source– Brazing /welding process– Tools (vacuum pump and refrigerant recovery comp. )– Smoking of service person? (Effectiveness of training)

The risk assessment results of mini-split from the progress report72.3 Cause of accidents in Japan• Statistics also indicates one of major cause of refrigerant
sudden release accidents are errors in service.
• Major sudden release has to be considered during andjust after services.
20181614121086420

Operation
Wrong Serv ice
Wrong Serv ice andInsta llation
Intentional
Not Clea r
Fata lty

InjuryTotal

Analysis of KHK data in 1998..

CFC, HCFC toxicity accidents

83.1 A2L Flammability• Historically, ammonia has been
exempted from “flammable gas
requirements” in many standards
or regulations, although it isflammable.
• Class 2L was originally proposed
to express ammonia flammability
more precisely and to extend its
exemptions.

BV (m/s)Hydrogen

2.91

Ethylene

0.75

CO0.11-0.43

Propane0.43

Iso-Butane

0.38

Methane

0.37

R152a

0.23

Ammonia

0.07

R143a

0.07

R320.07• Burning velocity was chosen to0.02-0.06
classify 2L refrigerants in ISO817 R1234yf
R22, R410A
and ASHRAE 34. Conventional
The data reported by Ecole des Mines
indices are not effective.
or quoted from the combustion
textbooks.

93.2 Practical combustion of 2L• Refrigerants in 2L class burns slowly even stagnatedconditions and do not Flash and hard to ignite when flowing.
• Flammability of 2L is far less than lubricant and brazing gas.

PropaneAmmonia

R152a

R32

These tests are carried out by Factory Mutual Research Center in the US in 1996.

R32

R32+Ether oil

R22+Mineral Oil

103.3 Real risk in brazing• If we see the flames in the same scale, thedifference is clear.
• Mineral oil has lower surface tension, resulting
in fine mist and large flame.
• A2Ls have much smaller combustion energy
per mass than lubricant.

R32

R32+Ether oil

R22+Mineral Oil

The tests are carried out by Daikin and presented in the JRAIA Kobe Symposium 2000

113.4 Open flame ignition• Combusting gas flame does not spread to leaking
2L refrigerant except ammonia, as convection
velocity is higher than BV.
• However, candle can ignite 2L.

The tests are carried out by Daikin.

123.5 Minimum Ignition Energy (MIE)• MIE is dominated by burning velocity basically.
• Quenching effect of electrode significantly affects
MIE with low burning velocity substances.
• BV affects probability of ignition significantly.
1000000

Thick electrodes

10000010000

1000

1/BV5MIE(mJ)

100
101/BV31

Theoretical(Thin Electrodes)

0.1

0.01
110100

BV(cm/s)

The data aremeasured by Dr.
Takizawa :AISTand are quoted
from quoted fromvarious publishedliterature.

13

3.6 Relay test results• Large power disconnection is necessary to ignite A2L with
BV<8 cm/s but 10 cm/s? IEC WG9 agreed the criteria 3 ɸ
5kVA and 1ɸ 2.5 kVA for R32.
• Most portable service tools have power below the criteria.
20

A2L
UL Data(Short cycle)

Ignited
FailedDisconnect Power (kVA)

10AIST Data
AIST Data with
1/BV4 extension

The data are measured byDr. Takizawa :AIST andare quoted from AHRI
report measured by UL.

Criteria

15R1234yf R32

10BV(cm/sec)

15

143.7 Pooling Effect• IEC/ISO Joint working group developed the formula
mmax=2.5 x LFL (5/4)x h0 x A(1/2)
assuming stagnation with minimum velocity.
• Fast flow results in more homogeneous unlikely to makesignificant flammable cloud, if the charge follows the formula.
160

Height from Floor (cm)140

Release height
180cm

120
100

Release Condition
Gas:HFC-134a
Amount:1300g
Port Size:f 22 cm
Rate:70g/min
Velocity:<0.1cm/s

806090cm50cm

40200010cm
510152025
Concentration of R134a in Air [vol%]Just after the End of Release

30Details are published in ASHRAE SE-99-19-2
Experimental and Numerical Analyses of Refrigerant
Leaks in a Closed Room15

3.8 Difference in risk with rapid release• CFD results indicate:– If flow velocity isconsidered, A2L does
not generate flammablecloud.
LFL– Flow speed is too highto ignite whereconcentration is highenough.
– Where velocity is low
enough, concentration isLFL
too low.
+speed• Accidental rapid release inservice or else is almost
impossible to ignite with A2L.
• Stagnation (pooling) is theissue.

R32Propane

10 m

200 g /min release
The data are calculated by Daikin

16

3.9 Difference between 2L and 3• A2L class refrigerants dilute below LFL quickly due to heavy
molecule and high LFL.
• Opening doors and windows are effective for 2Ls to avoid
ignition, in case of accidental release during service.

R290（60g/min)

Propane (60 g/min)

CFD results (Red: LFL)

R32 (250g/min)

R32 (250 g/min)17

3.10 Decomposition Products• Decomposition with combustion equipment or electric heater canhappen with all CFCs, HCFCs, and HFCs regardless offlammability (Tokyo university of science measurement results.)• It can reach fatal concentration, but it smells.

The data are quoted form the progress report of the project.

18

4. Overall Relative Risk
Concentration limit Other factor
HC Flammability Limit

40 g/m3

R22 Toxicity Limit

210 g/m3

A2L Flammability Limit

300 g/m3<

Ignition source of HC is stillless than population, but
considerably exists.

Ignition source density of A2L
is far less than population• Flammability limit of A2L is higher than toxicity limit of R22.
• Human density is much higher than the density of A2L
ignition sources in most spaces.
• Approximated flammability risk of A2L is smaller thantoxicity risk of R22.
• So, extreme care shall be taken with A2Ls for locations
where experienced toxicity accidents with R22. (e.g.
underground machinery rooms, piping pits, refrigerated food factory)

19

5. Other issues than flammability• HFC has higher polarity in molecule than HCFC. Moisture isabsorbed to most lubricant and damages the system (POE oil
decomposition and other reaction).
• Large organic molecules are hard to solve to HFC refrigerants.
Higher cleanliness of the refrigeration system is necessary to avoid
sludge clogs at expansion device or else where.
• Pressure of R32 is slightly higher than R410A and about 1.6 times
higher than R22.
• R32 has smaller molecular size than R22. Dryer (Molecular sieve)
has to be suitable material.

Many service procedures, tools and components
are different from ones for HCFCs and CFCs inaddition to flammability.
Care has to be taken for such differences.

20

6. Conclusion• A2L refrigerants are commercialized in some partsof the world and will be in other parts.
• Relatively higher risk in services for A2Ls.
• Flammability risk with A2L does not appear so high,as they are;
– Hard to ignite due to high MIE and low BV– Unlikely to make flammable cloud due to high
LFL in mass and volume.
• However, care for flammability has to be taken.
• In addition, care for HFC is necessary.
• Appropriate training for 2L refrigerants is necessary.

21END
Thank you for your attention!