Danfoss DHP-A Service Instructions Manual page 42

Cause
7. The high pressure switch does not
open.
8. The high pressure switch opens too
soon.
9. External system shunt that closes
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.
40 – Service instructions VMGFC302
Troubleshooting
•
Incorrect pressure switch installed.
Same or higher break pressure than
the high pressure switch. See mark-
ing.
•
Pressure switch fault, opens at a
higher pressure than indicated (mark
pressure). Check using the manome-
ter apparatus.
•
Defective pressure switch, never
opens.
•
Incorrect pressure switch installed. As
low or lower break pressure than
operating pressure switch. See mark-
ing.
•
Pressure switch fault, opens at a lower
pressure than indicated (mark pres-
sure). Check using the manometer
apparatus.
•
Defective pressure switch, always
open.
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 thermo-
stats/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 overheat-
ing is correct for the specific refrigerant.
Remedy
If the high pressure switch does not
open, replace it.
If the high pressure switch opens too
soon or is always open, replace it.
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 equip-
ment, the heating system can be adjus-
ted according to the system solution for
large pressure drop.
Follow the correct procedure (depend-
ing on type of refrigerant) to add the cor-
rect amount of refrigerant.
If there appears to be a leak in the refrig-
erant circuit, carry out leak tracing and
any necessary corrective action.