Danfoss Gas Detection Unit
Gas detection for machine rooms: gas values, alarms, errors and maintenance days per sensor.
Danfoss Gas Detection units watch the air in machine rooms and cold stores for ammonia, CO2, hydrocarbons and HFC refrigerants, and switch alarm relays at four thresholds. This Modbus RTU template reads gas values, alarm and error bits, thresholds and maintenance data of each sensor into ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 98, read and write
- Brand
- Danfoss
- Key readings
- Gas concentration · Average gas value · Alarm status · Error code · Alarm thresholds · Days until maintenance · Sensor sensitivity
- Available commands
- Device address
- Compatible models
- GDA · GDC · GDH · GDHC · GDHF · Danfoss Gas Detection units in Basic, Premium and Heavy Duty versions
- Last updated
Registers (98)
97 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Sensor 1 Current Value (compressed) | Read | ||||
| Sensor 1 Average Value (compressed) | Read | ||||
| Sensor 2 Current Value (compressed) | Read | ||||
| Sensor 2 Average Value (compressed) | Read | ||||
| Sensor 3 Current Value (compressed) | Read | ||||
| Sensor 3 Average Value (compressed) | Read | ||||
| Sensor 1 Type and Range (compressed) | Read | ||||
| Sensor 2 Type and Range (compressed) | Read | ||||
| Sensor 3 Type and Range (compressed) | Read | ||||
| Current Temperature (compressed) | °C | Read | |||
| Sensor 1 Gas Type | Read | ||||
| Sensor 1 Measuring Range | Read | ||||
| Sensor 1 Divisor | Read | ||||
| Sensor 1 Current Value | Read | ||||
| Sensor 1 Average Value | Read | ||||
| Sensor 1 Error | Read | ||||
| Sensor 1 Alarm Status | Read | ||||
| Sensor 1 Relays and Digital Inputs | Read | ||||
| Sensor 1 Alarm Threshold 1 | Read | ||||
| Sensor 1 Alarm Threshold 2 | Read | ||||
| Sensor 1 Alarm Threshold 3 | Read | ||||
| Sensor 1 Alarm Threshold 4 | Read | ||||
| Sensor 2 Gas Type | Read | ||||
| Sensor 2 Measuring Range | Read | ||||
| Sensor 2 Divisor | Read | ||||
| Sensor 2 Current Value | Read | ||||
| Sensor 2 Average Value | Read | ||||
| Sensor 2 Error | Read | ||||
| Sensor 2 Alarm Status | Read | ||||
| Sensor 2 Relays and Digital Inputs | Read | ||||
| Sensor 2 Alarm Threshold 1 | Read | ||||
| Sensor 2 Alarm Threshold 2 | Read | ||||
| Sensor 2 Alarm Threshold 3 | Read | ||||
| Sensor 2 Alarm Threshold 4 | Read | ||||
| Sensor 3 Gas Type | Read | ||||
| Sensor 3 Measuring Range | Read | ||||
| Sensor 3 Divisor | Read | ||||
| Sensor 3 Current Value | Read | ||||
| Sensor 3 Average Value | Read | ||||
| Sensor 3 Error | Read | ||||
| Sensor 3 Alarm Status | Read | ||||
| Sensor 3 Relays and Digital Inputs | Read | ||||
| Sensor 3 Alarm Threshold 1 | Read | ||||
| Sensor 3 Alarm Threshold 2 | Read | ||||
| Sensor 3 Alarm Threshold 3 | Read | ||||
| Sensor 3 Alarm Threshold 4 | Read | ||||
| Sensor 1 Manufacturing Day and Month | Read | ||||
| Sensor 1 Manufacturing Year | Read | ||||
| Sensor 1 Serial Number | Read | ||||
| Sensor 1 Unit Type | Read | ||||
| Sensor 1 Operating Days | d | Read | |||
| Sensor 1 Days Until Maintenance | d | Read | |||
| Sensor 1 Operating Day of Last Calibration | d | Read | |||
| Sensor 1 Maintenance Interval | d | Read | |||
| Sensor 1 Remaining Days Previous Period | d | Read | |||
| Sensor 1 Sensor Sensitivity | % | Read | |||
| Sensor 1 Calibration Count | Read | ||||
| Sensor 1 Calibration Tool Type | Read | ||||
| Sensor 1 Calibration Tool Number | Read | ||||
| Sensor 1 Long Term Average Gas Concentration | Read | ||||
| Sensor 1 Highest Gas Concentration | Read | ||||
| Sensor 1 Lowest Temperature | Read | ||||
| Sensor 1 Highest Temperature | Read | ||||
| Sensor 2 Manufacturing Day and Month | Read | ||||
| Sensor 2 Manufacturing Year | Read | ||||
| Sensor 2 Serial Number | Read | ||||
| Sensor 2 Unit Type | Read | ||||
| Sensor 2 Operating Days | d | Read | |||
| Sensor 2 Days Until Maintenance | d | Read | |||
| Sensor 2 Operating Day of Last Calibration | d | Read | |||
| Sensor 2 Maintenance Interval | d | Read | |||
| Sensor 2 Remaining Days Previous Period | d | Read | |||
| Sensor 2 Sensor Sensitivity | % | Read | |||
| Sensor 2 Calibration Count | Read | ||||
| Sensor 2 Calibration Tool Type | Read | ||||
| Sensor 2 Calibration Tool Number | Read | ||||
| Sensor 2 Long Term Average Gas Concentration | Read | ||||
| Sensor 2 Highest Gas Concentration | Read | ||||
| Sensor 2 Lowest Temperature | Read | ||||
| Sensor 2 Highest Temperature | Read | ||||
| Sensor 3 Manufacturing Day and Month | Read | ||||
| Sensor 3 Manufacturing Year | Read | ||||
| Sensor 3 Serial Number | Read | ||||
| Sensor 3 Unit Type | Read | ||||
| Sensor 3 Operating Days | d | Read | |||
| Sensor 3 Days Until Maintenance | d | Read | |||
| Sensor 3 Operating Day of Last Calibration | d | Read | |||
| Sensor 3 Maintenance Interval | d | Read | |||
| Sensor 3 Remaining Days Previous Period | d | Read | |||
| Sensor 3 Sensor Sensitivity | % | Read | |||
| Sensor 3 Calibration Count | Read | ||||
| Sensor 3 Calibration Tool Type | Read | ||||
| Sensor 3 Calibration Tool Number | Read | ||||
| Sensor 3 Long Term Average Gas Concentration | Read | ||||
| Sensor 3 Highest Gas Concentration | Read | ||||
| Sensor 3 Lowest Temperature | Read | ||||
| Sensor 3 Highest Temperature | Read | ||||
| Modbus Device Address | Write |
Loading registers…
Send your device list
If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Show the gas value of every detector in a machine room on one dashboard next to the refrigeration plant.
- Get an email when an alarm bit of a sensor turns on, or when the error word is not 0.
- Follow days until maintenance and plan the calibration visit before the interval runs out.
- Watch sensor sensitivity over months to see when a sensor head is due for replacement.
- Keep a history of the highest measured concentration as evidence for leak checks.
Installation
Wire the Bus A and Bus B terminals of the gas detection unit to the RS485 port of the ModbusCloud Gateway, with a 120 ohm resistor at both ends of the bus.
Give each unit a unique Modbus address and set the bus to 19200 baud, 8 data bits, even parity, 1 stop bit.
In ModbusCloud, add a Modbus device (RTU) with that address and import this template.
Read the gas type, range and divisor of each sensor and check that the current value divided by the divisor matches the unit display.
Set alarm rules on the alarm status and error registers of the sensors you use.
Things to watch for
Why is the gas value 100 times too high?
Gas values and thresholds are sent multiplied by the divisor of the sensor, which depends on the measuring range. Read the divisor register of the same sensor and divide by it, for example 314 with divisor 100 is 3.14.
How do I read the alarm status word?
Bits 4 to 7 are alarm 1 to 4 and bits 12 to 15 are the self hold of alarm 1 to 4. A value of 16 means alarm 1 is active; 0 means no alarm. An alarm rule on greater than 0 catches every stage.
Can I change thresholds or acknowledge alarms over Modbus?
No. The only register you can write is the device address, register 333 with function 16. All other settings are blocked for safety reasons and stay on the unit itself. After writing a new address the unit only answers on that address.
The unit answers irregularly. What should I check?
Poll each address no faster than every 100 ms, and with a short polling cycle add a pause of more than 550 ms per cycle. Check even parity and 1 stop bit, and the 120 ohm termination at both ends.
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