Danfoss DHP-AX Installation And Service Instructions Manual page 49

Cause
9. External system shunt that clo-
ses on time setting.
10. Incorrectly facing non-return
valve with too high opening
pressure.
11. Large pressure drop in the
heating system.
12. Overfilled refrigerant circuit.
13. Blocked condenser on the
water side.
14. Blocked condenser on the
refrigerant side.
Troubleshooting
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.
• 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 pressure exceeds the non-
return valve's opening pressure.
• 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 pressure drop.
Using manometer apparatus and ther-
mometer, check that the unit's overhea-
ting is correct for the specific refrigerant.
If there is no strainer in the heating sys-
tem, there is a risk of dirt sticking in the
condenser and blocking it. Unfortunately
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 circulation pumps
work (for circ.pumps with a bleed screw,
unscrew it and feel if the pump rotor
rotates using a screwdriver).
Then read the temperature on both con-
nection 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.
Using manometer apparatus and ther-
mometer, check that the unit's overhea-
ting is correct for the specific refrigerant.
VMBMH302
Remedy
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.
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.
If necessary, clean/flush the heating sys-
tem.
Open closed thermostats/valves.
If there is not sufficient pressure
equipment, the heating system can be
adjusted according to the system solu-
tion for large pressure drop.
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 refri-
gerant circuit, carry out leak tracing and
any necessary corrective action.
If the condenser is thought to be block-
ed, try flushing it. If this does not work, it
must be replaced
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
Service – 49