Troubleshooting A Heating System Installation; Diagnosing The Installation - Danfoss DEVItector II V2 User Manual

User Guide

7. Troubleshooting a heating system installation

Troubleshooting a heating system involves a diagnosis of
1. Power supply
2. Controller (thermostat) and sensors
3. Heating element(s)/heating cable(s) followed by a correction of the fault.

Diagnosing the installation

Note: You must follow this guide to ensure a safe and
optimal troubleshooting.
Warning. Conductive building materials, e.g. metal
mesh in concrete, metal water pipe, drain pipe, etc.,
might be in contact with cable under test. These
building materials or other metal parts might be not
grounded and, in this way, be dangerous during the
testing process.
1. Make sure that the circuit breakers, the optional
Residual Current Device (RCD) and the mains
voltage all are working properly and have correct
size/ value.
Do not proceed until this is the case.
2. Test the controller/thermostat:
Does it activate/deactivate, when the temperature
setting is changed?
If Yes go to step 5.
3. Check the external temperature sensor.
The resistance value [kOhm] for sensors may be
found in the installation instructions or in the
product catalogue.
If the sensor is faulty, replace it and continue with
step 5.
4. Repair or replace the controller/thermostat.
5. Check the output of the controller/thermostat.
If it is missing, continue with step 4.
6. If no faults appeared in the above tests, the
heating element/heating cable is probably faulty.
If a mistake occurs, check the heating element/
cable before proceeding.
14 | ©Danfoss | FEC | 2022.07
DEVItector™ II V2
7. Disconnect the thermostat from the heating
element/cable before starting the measurement of
the resistances.
Note: De-energize all power circuits before the
disconnecting.
8. Measure the resistance of the heating element/
cable using an ohm-meter. Resistance values of
heating element/cable may be found in the Data
Sheet, Product Catalogue, etc.
Compare the measured resistance of the heating
element/cable to the resistance of a representative
heating element.
If the two values differ significantly, you probably
have a faulty heating element/cable.
9. Measure the insulation resistance of the heating
element/cable using an megohmmeter. The
insulation resistance should read >20 MOhm after
one minute at min. 500 V, preferably 2,5 kV.
If the insulation resistance value is lower than
20 MOhm, you probably have a faulty heating
element/cable.
Note: Real insulation resistance of heating
cables is usually more than 100 MOhm or even
1000 MOhm, and depends from cable length,
cable age, moisture conditions, etc.
10. A heating cable fault has now been verified and
you may start the troubleshooting process.
BC421332622232en-010101