7.2 Troubleshooting DHW
Problem
Possible cause
Solution
Strainer in supply or return line clogged.
Clean strainer(s).
DHW circulation pump out of order or with
too low setting.
Check circulation pump.
Defective or clogged non-return valve.
Replace – clean.
No electricity.
Check.
Wrong setting of automatic controls, if any.
To adjust an electronic controller for
DHW, pls. note enclosed instructions for
electronic controller.
Scaling of the plate heat exchanger.
Replace – rinse out.
Defective motorized valve.
Check (use manual function) – replace.
Defective temperature sensors.
Check – replace.
Too little or no DHW.
Defective controller.
Check – replace.
DCW is being mixed with the DHW, e.g. in a
defective thermostatic mixing valve.
Check – replace.
Hot water in some taps but not in all.
Defective or clogged non-return valve on
circulation valve.
Replace – clean.
Tap temperature too high; DHW tap load
too high.
Thermostatic valve adjusted to a too high
level.
Check – set.
Scaling of the plate heat exchanger.
Replace – rinse out.
Temperature drop during tapping.
Larger DHW flow than the substation has
been designed for.
Reduce DHW flow.
Thermostatic control valve does not close
Temperature difference between DH
supply and DHW set point too low.
Lower the set point temperature or increase
the DH supply temperature.
18 | © Danfoss | 2019.01
VI.CW.Y5.02 / LUK42260
Operating Guide Termix VMTD MIX Compact 28
