7.3 Troubleshooting HE
Problem
Possible cause
Solution
Too little or no heat.
Strainer clogged in DH or HE circuit
(radiator circuit).
Clean gate/strainer(s).
The filter in the energy meter on DH circuit
clogged.
Clean the filter (after consulting the DH
plant operator).
Defective or wrongly adjusted differential
pressure controller.
Check the operation of the differential
pressure controller – clean the valve seat if
required.
Sensor defective – or possibly dirt in the
valve housing.
Check the operation of the thermostat –
clean the valve seat if required.
Automatic controls, if any, wrongly set or
defective - possibly power failure.
Check if the setting of the controller
is correct – see separate instructions.
Check the power supply. Temporary
setting of motor to “manual” control – see
instructions on automatic controls.
Pump out of operation.
Check if the pump is receiving power and
that it turns. Check if there is air trapped in
the pump housing – see pump manual.
The pump is set at too low speed of
rotation.
Set the pump at higher speed of rotation.
Pressure drop – the pressure drop on
the radiator circuit shows lower than
recommended operating pressure.
Fill water on the system and check the
functioning of the pressure expansion
vessel if required.
Air pockets in the system.
Vent the installation thoroughly.
Limiting of the return temperature adjusted
too low.
Adjust according to instructions.
Defective radiator valves.
Check – replace.
Uneven heat distribution in building
because of incorrectly set balancing valves,
or because there are no balancing valves.
Adjust/install balancing valves.
Diameter of pipe to substation too small or
branch pipe too long.
Check pipe dimensions.
Uneven heat distribution.
Air pockets in the system.
Vent the installation thoroughly.
DH supply temperature too high.
Wrong setting of thermostat or of
automatic controls, if any.
Adjust automatic controls, – see
instructions for automatic controls.
Defective controller. The controller does
not react as it should according to the
instructions.
Call automatic controls manufacturer or
replace the regulator.
Defective sensor on self-acting thermostat.
Replace thermostat – or sensor only.
DH supply temperature too low.
Wrong setting of automatic controls, if any.
Adjust automatic controls – see instructions
for automatic controls.
Defective controller. The controller does
not react as it should according to the
instructions.
Call in automatic controls manufacturer or
replace controller.
Defective sensor on self-acting thermostat.
Replace thermostat – or sensor only.
Wrong placement/fitting of outdoor
temperature sensor.
Adjust location of outdoor temperature
sensor.
Strainer clogged.
Clean gate/strainer.
VI.CW.Y5.02 / LUK42260
© Danfoss | 2019.01 | 19
Operating Guide Termix VMTD MIX Compact 28
