3.8  Installation Test As DGS is a digital device with self-monitoring, 
all internal errors are visible via the LED and 
MODBUS alarm messages. 
All other error sources often have their origins in 
other parts of the installation.
For fast and comfortable installation test we 
recommend proceeding as follows.
Optical Check 
Right cable type used. 
Correct mounting height according to definition 
in the section about mounting. 
LED status – see DGS trouble shooting. 
Functional test (for initial operation and 
maintenance) 
Functional test is done by pressing the test 
button for more than 8 seconds and observing 
that all connected outputs (Buzzer, LED, Relay 
connected devices) are working properly. After 
deactivation all outputs must automatically 
return to their initial position. 
Zero-point test (if prescribed by local 
regulations) 
Zero-point test with fresh outdoor air. 
A potential zero offset can be read out by use of 
the Service Tool. 
Trip test with reference gas (if prescribed by 
local regulations) 
The sensor is gassed with reference gas (for this 
you need a gas bottle with pressure regulator 
and a calibration adapter). 
Action Reaction
Buzzer
Reaction
Light
Warning relay 1** 
SPDT NO
(Normally Open)
Critical  relay 3** 
SPDT NC
(Normally closed)
Loss of power to DGS OFF OFF X (closed)
Gas signal < warning alarm 
threshold 
OFF GREEN
Gas signal > warning alarm 
threshold 
OFF RED Slow flashing X (closed)
Gas signal > critical alarm 
threshold
ON RED Fast flashing X (closed) X (closed)
Gas signal ≥ critical alarm 
threshold, but ackn. button 
pressed
OFF  
(ON after 
delay)
RED Fast flashing X (closed)* (open)*
No alarm, no fault OFF GREEN
No fault, but maintenance due OFF GREEN Slow 
flashing
Sensor communication error OFF YELLOW
DGS in special mode OFF YELLOW flashing
Alarm thresholds can have the same value, therefore both the relays and the Buzzer and Light can be triggered 
simultaneously.
The alarm thresholds have a hysteresis of app. 5%
*  whether to include the relay status with the acknowledge function or not is user defined.
** If the DGS has two sensors and the "Room Mode" is configured to "2 rooms", then relay 1 acts as a critical 
relay for sensor 1 and relay 3 acts as a critical relay for sensor 2. Both relays are SPDT NC. The Buzzer and Light 
operation is independent of the "Room Mode" setting.
In doing so, the set alarm thresholds are 
exceeded, and all output functions are activated. 
It is necessary to check if the connected output 
functions are working correctly (e.g. the horn 
sounds, the fan switches on, devices shut down). 
By pressing the push-button on the horn, the 
horn acknowledgement must be checked. After 
removal of the reference gas, all outputs must 
automatically return to their initial position.
Other than the trip testing, it is also possible to 
perform a functional test by means of calibration. 
For further information, please refer to the User 
Guide. 
Comparing sensor gas type with DGS 
specification
The replacement sensor specification must match 
the DGS specification. 
The DGS software automatically reads the 
specification of the connected sensor and 
compares with the DGS specification. 
This feature increases the user and operating 
security. 
New sensors are always delivered factory-
calibrated by Danfoss. This is documented by the 
calibration label indicating date and calibration 
gas. A re-calibration is not necessary during 
commissioning if the device is still in its original 
packaging (including air-tight protection by 
the red protective cap) and if the calibration 
certificate has not expired
User Guide | Danfoss Gas sensor, type DGS
6 | BC291049702513en-000201 © Danfoss | Climate Solutions | 2022.01