Cause
Troubleshooting
Remedy
8. The high pressure switch
opens too soon.
▪
Incorrect pressure switch installed. As low or lower
break pressure than operating pressure switch. See
marking.
▪
Pressure switch fault, opens at a lower pressure than
indicated (mark pressure). Check using the manome-
ter apparatus.
▪
Defective pressure switch, always open.
If the high pressure switch opens too soon
or is always open, replace it.
9. External system shunt
that closes on time setting.
Check for shunts or valves in the system, which are timer-
controlled, that close down the entire or too large a part of
the heating system.
Always ensure that there is a sufficiently
large water volume for the heat pump to
work against, i.e. for the heat to give off its
heat to.
10. Incorrectly facing non-
return valve with too high
opening pressure.
▪
Check the system’s direction of flow and that the non-
return valve is turned the correct way.
▪
Check that the heat pump’s external available pres-
sure exceeds the non-return valve’s opening pressure.
If the non-return valve is facing the wrong
way, turn it.
If the non-return valve has too great an
opening pressure, replace it.
11. Large pressure drop in
the heating system.
▪
Dirt in the heating system.
▪
Closed or partially closed thermostats/valves in the
heating system.
▪
Under dimensioned pipe system. Check that the HP’s
external available pressure exceeds the system pres-
sure drop.
If necessary, clean/flush the heating system.
Open closed thermostats/valves.
If there is not sufficient pressure equip-
ment, the heating system can be adjusted
according to the system solution for large
pressure drop.
12. Blocked condenser on
the water side.
If there is no strainer in the heating system, there is a risk
of dirt sticking in the condenser and blocking it. Unfortu-
nately there is no easy way of checking if the condenser is
blocked.
You can carry out a test by allowing the compressor and
circulation pumps to remain in operation and after a while,
check that the pressure pipe becomes hot and that the cir-
culation pumps work (for circ.pumps with a bleed screw,
unscrew it and feel if the pump rotor rotates using a screw-
driver).
Then read the temperature on both connection pipes to
the condenser:
If the temperature difference is <3°C, the condenser is
probably blocked.
If the temperature difference is 3-13°C, it is probably not
blocked.
If the temperature difference is >13°C, the condenser is
probably blocked.
If the condenser is thought to be blocked,
try flushing it. If this does not work, it must
be replaced
13. Blocked condenser on
the refrigerant side.
Using manometer apparatus and thermometer, check that
the unit’s overheating is correct for the specific refrigerant.
If the condenser is thought to be blocked
by oil for example, try blowing nitrogen
through it to release the oil. If this does not
work, it must be replaced
14. Overfilled refrigerant cir-
cuit.
Using manometer apparatus and thermometer, check that
the unit’s overheating is correct for the specific refrigerant.
Follow the correct procedure (depending
on type of refrigerant) to add the correct
amount of refrigerant.
If there appears to be a leak in the refriger-
ant circuit, carry out leak tracing and any
necessary corrective action.
Service Instructions
DHP-AQ
Danfoss Heating Solutions
VMGFJ202
17
