Risk Assessment for facility A/CWorking Group for Risk Assessment of Lower Flammability Refrigerant
Introduction○Facility A/C, commercial packaged air conditioner for facilities, has a wide variety of applications such as A/C
for human comfort, A/C in a factory for goods and A/C for special users(for server rooms and clean rooms).Fig1
Ratio of projects delivered with Facility A/C○Main characteristics(1)・For goods approx.40%
1. Although the Facility A/C does not have individual air conditioning system,some systems are larger than VRF system in capacity(refrigerant amount).
Offices2. There is a case where multiple refrigerant systems are connected to theFactorylarge capacity indoor unit.
Hospital
3. There is a case where it is installed in a room with very high thermal load
Educationsuch as server room and a room for special use.
facilities
Accommodation
4. There are ignition sources (blast furnaces, drying furnaces, etc.) which
Residenceare unique to Facility A/C.
5. There is a case where the ratio of refrigerant amount to a room volume
Special user
(LFL ratio>1) is high⇒ Even though it mainly has pair connection,
Unknown, others
・For human comfort approx. 60%
the countermeasure which was extended from that of commercial A/C
図1Fig.1
shall not be accepted.

System Comparison○System comparison per product type
Types of products

Commercial A/C

VRF System

Facility A/C

Refrigeration capacity※System
Main installation system

Less than 3 tons
1 unit : 1 to 4 units
All indoor units are installedin the same space

3 tons or more - less than 20 tons
1 to 3 units : 1 to 64 units
Each indoor unit is installed
in a separate space

Main indoor unit type

Ceiling cassette type, Ceiling suspended type,
Wall mounted type, Built-in duct type,
Floor mounted type(slim type)

Ceiling cassette type, Ceiling suspended type,
Wall mounted type, Built-in duct type,
Floor mounted type (for perimeter)Less than 20 tons
1 to 3 units : 1 unit
There are multiple refrigerant circuits per indoor unit.
Multiple units are installed per room.
Floor mounted type,Floor mounted type (built-in compressor)
For computer room(ceiling suspended),
For computer room（floor mounted air outlet)
For clean room

Air cooled type horizontal flow, Ice thermalstorage type (air cooled) horizontal flow

Air cooled type Vertical flow, Ice thermal
storage type (air cooled) Vertical flow,
Water cooled type (in a machinery room )Office, Kitchen,/Dining hall, Factory(general),Karaoke room (highly sealed space)
Above the ground(rooftop), Install on every
floor, Semi-underground,
Indoor installation (machinery room )Installation(Outdoor unit : Indoor unit)

Main outdoor unit type

Office, Kitchen,/Dining hall, Factory(general),Karaoke room (highly sealed space)
Above the ground(rooftop), Install on every
floor, Semi-underground,
Small and narrow space (alley, gap)

Main indoor installation location
Main installation location ofoutdoor unit

Same as on the left (common with VRF system)
Condensing unit (without compressor)
Factory(foundry, etc.), Computer room（floormounted air outlet)Clean room, Dining hallSame as on the left (same as VRF system)※High Pressure Gas Safety Act, Refrigeration Safety Regulation○Characteristics per life stage
Life stage
Facility A/CTransportation○Example of 100% outside air processing

Storage

Installation

Repair/service

Disposal

全熱交換気
Total heatexchanger with
温度調節機能有temperature
control function

UsageConclusion

Air conditioner

Safety Measure Effect Verification (1)1) A large portion of them are used for goods(not for human comfort), and their uses vary
widely. Some are used in spaces where ignition sources are present that cannot be removed.
Others are used in applications where immediate restoration of operation is required after
such problem as refrigerant leakage.
2) Multiple air conditioners are often installed in a single space, where some air conditioners areinstalled or repaired, or disposed while other air conditioners are in operation.
3) Most of the indoor units are floor mounted type, which are at a risk of creating flammableregions near the floor in case of a refrigerant leak.

○It shall be verified whether the air can be circulated at theminimum airflow rate and air velocity with a floor-mounted type.
Verified air flow rate and velocity range

Analytical model
Pressure

3.7m3/min

Safety Measure Effect Verification (2)○It shall be verified whether the air can be circulated at the minimum airflow rate and air velocity in araised floor air conditioning system. Relationship between the air flow rate and velocity of air circulation from analysis.
10㎏/ｈ leakege

Pressureboundary

R32
R1234yf

M=52(R32)

10㎏/h suppositionof leakage

LFL/4(Refrigerant amount is large)
Analytical model

Analytical result of ventilation
effect(1)Air outlet opening

Analysis of Air circulation effect in raised floor 2
3.53m*R1234yfー75kg/h leakage(when leakage finished)

Air inlet

In the rapid
leakage withrefrigerant
amount LFL/4,
flammable region
is not formed since
air is circulated up
to the upper end of
an indoor unit.

Analytical result of ventilation
effect(2)No volume which exceeds 0.5% of whole internal
volume(volume of 0.2522m3)

Time when leakage
finished

Flammable volume

4,000
R32
R1234yf

75㎏/h suppositionof leakage

Safety Measure Effect Verification (3)○Ventilation
effect for
the additional
measureswhen exceeding
SafetyMeasureEffectVerification(3)Refrigerantleak position（100×100）
75[kg/h]

75㎏/ｈ leakege

2.0m/sIn the rapid leakage with refrigerant amount
LFL/4, flammable region is not formed since
the air is circulated up to the upper end of anindoor unit.

Ventilating
opening*R1234yfー10kg/h leakage(when leakage finished)

M=52(R32)

Result of the air circulation by horizontal flow of direct flow type4.0m

Air Inlet opening

1.0m/sUnit [mm]Air exhaust opening(400x400)
Air flow rate

Analysis of Air circulation effect in raised floor 1

M=114(R1234yf)

M=114(R1234yf)

Symmetricboundarya) Refrigerant detectors and alarms shall be installed regardless of the estimated maximum
refrigerant concentration of leaked refrigerant.
b) Floor mounted indoor units shall have an air circulation function that goes into
operation when a refrigerant leak detector is triggered.
c) If the maximum refrigerant concentration of leaked refrigerant exceeds one-quarter ofthe LFL, additional safety measures (such as a shut-off valve or ventilation) are required.
d) Where an unremovable ignition source is present, refrigerant leak detectors shall be
installed closer to the area where refrigerant leak is likely than to the ignition sources.

9.6m3/minboundary

Cooling an equipment

Raised floor air conditioning analysis model

Intake air

Ventilation duct

・In important facilities, normal ventilation shall not be carried out since a large change in temperature isnot allowed. Therefore 100% outside air processing is required.
・There are indoor units with built-in compressor. ・Back-up units operate continuously even at the timeof maintenance and disposal in important facilities.

(Same as VRF system)

Exhaust airTime[min]In rapid leakage, flammableregion is not formed since air will
be ventilated.

Summary・Facility A/C is able to operate safely by taking safety measures
mentioned above.
・In the future, t is required to perform risk assessment for themodels excluded from this investigation such as integrated type.

Document
・Guideline of design construction for ensuring safety against refrigerant leakage from commercial packaged air conditioner for facilities using lower
flammability (A2L) refrigerants JRA GL-19:2016
・Requirements of ensuring safety against refrigerant leakage from Facility A/C using lower flammability (A2L) refrigerants JRA 4073:2016