Risk Assessment for VRF
Working Group for Risk Assessment Lower Flammability refrigerant

TargetIntroduction

Conclusion
Conclusion• Target is to make a proposal for safety measures which can achievetolerable ignition risk for VRF with lower flammability refrigerants
such as R32 .
• Risk factors are identified to be a large charge amount and somesevere installation cases in which flammable space appears easily.
• Ignition risk is evaluated using measurement results of leak rate
and CFD results to calculate size and duration of flammable space.

• In indoor operation, smoking with oil lighter by overtime worker
in office at night after ventilation stops makes a non-tolerable risk.
Shut-off valve, mechanical ventilation etc. can reduce risk totolerable level.
• In outdoor operation, boiler ignition near outdoor unit in semiunderground makes a non-tolerable risk. Some measures toexhaust the leaked refrigerant can reduce risk to tolerable level.
• Safety measures are summarized in safety guidelines of JRAIA.

SystemSystem

Typicalrisk
case
Typical
risk
case

••

14.0 – 168

Refrigerant charge

Operation

Type of indoorunitType of outdoorunit

5 – 104 kg (R410A)

Ceiling-concealed
duct type

Indoor units, max 64units, canbe operated individually••••••••Normal case

Severe caseContinuous 24 hour ventilation*1)

Ventilation stops at nightkW

Ceiling mounted cassette
Ceiling-concealed duct type
Ceiling-suspended type
Wall mounted type
Floor mounted typeHeat Pump
Heat Recovery
Water cooled unit

Indoor

G=26.3

A/CAirOfficeCeiling-suspended
type

Ventilation

DoorSmokingwith oil lighter

ONUnder cutwatercooled

0 6 12 16 24 hG=26.3Outdoor

G=26.3groundA/C

A/Cground*1) Air flow rate is assumed to be adequate.

Leakrate
andandprobability
Leakrateprobability•R32 charge amount : G [kg]Flammable
regionFlammable
area

Measured leak rate and probability based on service data.
SlowOFF

Semi-underground

Wall mounted
type

Floor mounted
type

ON

0 6 12 16 24 hOpen space
aircooled

G=88.1

X

Cooling capacity

Ceiling cassette

Both of normal and severe cases are evaluated.

XLarge charge amount and many types of units.

RapidBurstEvidence

Normal caseSevere caseContinuous 24 hour ventilation *1)

Ventilation stops at night

0.15

Leak rate [kg/h]<11 - 10

Cause of leakage

Pin-hole/Corrosion of pipe

Corrosion of heatexchanger

Probability[ppm/(unit・year)]indooroutdoor345
6130

a. Indoor leak rate

10 - 75a, b

Breaking of pipe

Observation ofleakage hole

None5(no compressor)1340

N x 10c134

c. Number of servicing report
indicating rapid leak
2010, Manufacturer B[number/year]

Refrigerant : R32

Burntsmell

Holesin pipe

(total)Indoor0101

Outdoor1337unit

Max < 10[kg/h]

Max < 75[kg/h]

0.00

Non-flammableregion

T=158 min *2)

V=0.0044 m3 (0.004%)

Flammable
regionV= 114 m3 (100%)

T=276 minSemi-underground

Open space

Flammable
regionFlammable
regionOutdoor

NWhitesmoke

Refrigerant : R32

0.05

N x 100(with compressor)

b. Outdoor leak rate

Indoor0.10

V= 0.04 m3 (-)

T=21 min

V=16.4m3 (15%)

V : Mean volume size of flammable region [m3], (ratio to all volume) [%]T : Duration of flammable region [min]*1) Air flow rate is assumed to be adequate.
*2) Hihara et al.，Progress at the University of Tokyo, JSREA, Progress report, 2013，pp.16

T=3852min

Refrigerant : R32

Risk assessment
Resultsof risk assessments

Safetymeasures
measures
Safety•• In severe cases, each safety measures are defined. These measures are effective also for R1234yf & ze in high moisture condition.

In severe cases, the ignition risks exceed tolerable risk.
not tolerable

Normal caseOperation 3.5 x 10-12
Installation 1.9 x 10-9
Repairing 8.7 x 10-11
Disposal 2.9 x 10-14-11

Outdoor[time/(unit・year)]

Installationcase

Severe casewithout
Life stage
measureLife stage

Indoortolerable

Operation 1.9 x 10
Installation 1.9 x 10-9
Repairing 1.4 x 10-9
Disposal 2.4 x 10-10
7.8 x 10-17
Storage～ 1.8 xwithmeasureVentillation
3.5 x 10-12
Operation 7.6 x 10-9 1.5 x 10-10
Shut off valve
Safety alarm
7.6 x 10-10
withoutwithmeasuremeasureOperation 1.7 x 10-6 2.5 x 10-13
Ventillation
Installation 1.1 x 10-8 1.9 x 10-6 Carring of portable
Repairing 3.6 x 10-7 2.1 x 10-6
leak detector,
Disposal 4.2 x 10-6 6.1 x 10-6and education
Refrigerant : R32

IndoorOutdoor

Safety measures
Choose one of measures shown below

Other thanfloor mountedtypeA) Ref. charge M ≦ 1/4 x LFL x A x height_of_leak_position
B) Mechanical ventilation with adequate air flow rateC) Shut-off valve

Floor mountedtypeA) Ref. charge M ≦ 1/4 x LFL x A x reaching_height_with_aircirculation
B) Mechanical ventilation with adequate air flow rateC) Shut-off valve

SemiundergroundA) Ref. charge M ≦ 1/2 x LFL x A x depthB) Mechanical ventilation
C) Air circulation

MachineryroomA) Mechanical ventilation operated at all times withadequate air flow rate

Documentation
Documentation••••

JRAIA : VRF Sub working, Risk Assessment for VRF System, 2015 Final report, JSREA, 2016
JRAIA : VRF Sub working, Risk assessment for VRF system with mildly flammable refrigerants, JSREA, Refrigeration, 2016/5
JRAIA, JRA GL-16:2016, Guideline of design construction for ensuring safety against refrigerant leakage from commercial air conditioners using lower
flammability (A2L) refrigerants
JRAIA, JRA 4070:2016, Requirements for ensuring safety against refrigerant leakage from commercial air conditioners using lower flammability (A2L)
refrigerants