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OVERALL MAXIMUM CHARGE SIZES :
Table 1: Safety classifications.
Safety classification Lower Flammability Level,
% in air by volume
Heat of combustion
J/kg
A1 No Flame propagation when tested at 60ºC and 101.3 kPa
A2, Lower Flammability >3.5 <19 000 Exhibits flame propagation when tested at 60ºC and 101.3kPa
A2L, Lower Flammability,
>3.5
proposed sub-classification <19 000 Exhibits flame propagation when tested at 60ºC and 101.3kPa
and has a maximum burning velocity of ≤10 cm/s when tested at
23ºC and 101.3kPa
A3, Higher Flammability ≥19 000 Exhibits flame propagation when tested at 60ºC and 101.3kPa
≤ 3.5
Flame propagation
Table 2: Summary of most common scenarios for A2 and A3 refrigerants.
Refrigerant
Boiling point
Safety group
LFL, kg/m
LFL, %
Auto ignition
temp, ºC
PL, kg/m ³
GWP
HC R600a -12 A3 0.038 1.8 460 0.011 3
HC R290 -42 A3 0.038 2.1 470 0.008 3
HC R1270 -48 A2 0.047 2.7 455 0.008 3
HC Care 30 -23 / -32 A3 0.041 2.0 460 - 3
HC Care 50 -43 / -49 A3 0.038 2.0 460 - 3
HFO R1234yf -29.4 A2
A2L
(proposed) 0.299 6.5 405 0.06 4
HFO R1234ze⁷ -19 A2L
(proposed) - 5.8⁸ 288 to 293 - 6
HFC R32 -51.7 A2
A2L
(proposed) 0.307 14.4 648 0.061 550
HFC R143a -47 A2 0.282 8.2 750 0.056 4300
HFC R152a -25 A2 0.13 4.8 455 0.027 120
Table 3: Direct expansion systems.
Area being cooled System location Max change, A2 refrigerants Max charge, A3 refrigerants
All areas Part or all of system below ground As below 1kg
General occupancy
-Class A Whole of system at ground level or
above 38 x LFL 1.5kg
General occupancy
-Class A Whole of system at ground level
or above and in an unoccupied
machine room or open air 132 x LFL 5kg
Supervised occupancy
-Class B Whole of system at ground level or
above and in human occupied area 10kg 2.5kg
Supervised occupancy
-Class B Whole of system at ground level or
above; compressor and receiver in
open air or machine room 25kg 2.5kg
Authorised access
-Class C Whole of system at ground level or
above and in human occupied area 10kg, or 25kg if <1 person per
10m², and there are sufficient
emergency exits 10kg
Authorised access
-Class C Whole of system at ground level or
above; compressor and receiver in
open area or machine room 25kg, or no restriction if <1
person per 10m² 25kg
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RACA Journal I March 2020
61