User guide

Application Guide | Gas detection in refrigeration systems
18 DKRCI.PA.S00.A1.02 | 520H12772 © Danfoss | DCS (MWA) | 2018.05
Actions triggered by gas
detection
The actions to be triggered when leaked
refrigerant is detected depends on the standard
applied. National regulations, especially the
“Occupational Exposure Limits”, varies from
country to country.
Actions for
Ammonia – R717
EN 378:2016 ISO 5149:2014 ASHRAE 34-2016 IIAR 2-2014
Up to 50 kg refrigerant At max. 157 ppm:
- Actuate an alarm
- Notify an authorised person
- Audible buzzer 15 dBA above background noise
level
- Flashing lamp
- Alarm to be inside the room
- For machinery rooms: Also outside the room,
which can be at a supervised location
- For machinery rooms: Start emergency ventilation
At max. 1000 ppm:
- Audible and visual
alarm
- Inside the machinery
room and outside
each entrance
- Start mechanical
ventilation
- Shut down
combustion
processes drawing
air from the room
(except if the
combustion is driving
the compressor)
Machinery rooms at max.
25 ppm:
- Audible and visual alarm
- Inside the machinery
room and outside each
entrance
- Alarm to monitored
location
- Stop non-emergency
ventilation (unless it is
designed to work with
R717)
Machinery rooms at max.
150 ppm also:
- Start emergency
ventilation
Machinery rooms at max.
40000 ppm also:
- De-energize compressors,
refrigerant pumps, and
normally closed valves
Not in machinery rooms at
max. 25 ppm:
- Alarm to monitored
location
- Other actions depends
on system type and
location
More than 50 kg
refrigerant
Same actions as above,
but starting at max. 500
ppm
At max. 30000 ppm also:
- Stop the system
- Stop the power supply
to everything which is
not Ex approved
Same actions as above,
but starting at max. 200
ppm
At max. 30000 ppm also:
- Stop the system
- Stop the power supply
to everything which is
not Ex approved
More than 3000 kg
refrigerant
Same as above, but also
- central alarm station
- specialized personnel
on site within 60 min of
alarm
More than 4500 kg
refrigerant
Same as above, but also:
- central alarm station
- specialized personnel
on site within 60 min of
alarm
Actions for refrigerants
other than ammonia
EN 378:2016 ISO 5149:2014 ASHRAE 34-2016
For all systems except
ventilated enclosures
and systems using
alternative risk
management
At 50% ATEL/ODL/RCL or 25% LFL (see Annex II):
- For flammable refrigerants: Stop the system
- Actuate an alarm
- Notify an authorised person
- Audible buzzer 15 dBA above background noise level
- Flashing lamp
- Alarm to be inside the room
- For occupancy A: Also outside the room, which shall be at a
supervised location
- For occupancy B and C: Only inside is needed
- For machinery rooms: Also outside the room, which can be at a
supervised location
- For machinery rooms: Start emergency ventilation
At OEL (see Annex III):
- Audible and visual alarm
- Inside the machinery room and
outside each entrance
- Start mechanical ventilation
- Shut down combustion
processes drawing air from
the room (except if refrigerant is
R744)
For ventilated
enclosures
If a detector is used for staring ventilation:
Start ventilation at 25% LFL (see Annex II)
Not applicable
For systems using
alternative risk
management
If a detector is used for staring ventilation:
Start ventilation at 50% ATEL/ODL/RCL or 25% LFL (see Annex II)
Not applicable