Danfoss DHP-AL Installation And Service Instructions Manual page 43

Cause
13. Drying filter blockage.
14. Blocked evaporator on the
water side.
15. Blocked evaporator on the
refrigerant side.
Problem – Alarm HP (high pressure pressure switch)
Cause
1. Blocked strainer in the heating
system.
2. Air in the heating system.
3. Closed or partially closed ther-
mostats/valves in the heating
system.
4. The circulation pump that is
defective or has jammed.
5. Shut-off main tap in heating
system.
6. Cable break or loose cable to
high pressure pressure switch.
Troubleshooting
Check the temperature difference above the dry-
ing filer. A one degree difference is permissible. If
the difference is greater than 1 degree, the filter is
blocked. Take a reading during operation.
If there is no strainer in the brine circuit, there is a
risk of dirt sticking in the evaporator and blocking
it. Unfortunately there is no easy way of checking if
the evaporator is blocked.
You can carry out a test by allowing the compres-
sor and circulation pumps to remain in operation.
Check that the circulation pumps work (for circ.
pumps with a venting screw, unscrew it and feel if
the pump rotor rotates using a screwdriver).
Then read the temperature on both connection
pipes to the evaporator:
If the temperature difference is <1°C, the evapora-
tor is probably blocked.
If the temperature difference is 2-6°C, it is probably
not blocked.
If the temperature difference is >6°C, the evapora-
tor is probably blocked.
Using manometer apparatus and thermometer,
check that the unit's overheating is correct for the
specific refrigerant.
Then check in the same way that the unit's cool-
ing is correct. See separate instructions for cooling
techniques.
Troubleshooting
Check that the strainer is not blocked.
Listen for air in the heat pump and heating system. Bleed the heating system circuit according to
Check that the thermostats/valves in the heating
system are open.
Is there voltage to the circulation pump?
Check that the main tap is open.
• Check that both cables are connected on the
pressure switch.
• Using the buzzer, check that there are no cable
breaks. In order to do this, disconnect the cables
from the pressure switch and circuit board.
VMBME102
Remedy
If the drying filter is sealed, replace it.
If the evaporator is thought to be blocked, try
flushing it. If this does not work, it must be
replaced
If the evaporator 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
Remedy
Clean the strainer if necessary.
the installation instructions.
Open closed thermostats/valves.
In the control computer's manual test menu
check that the circulation pump is active.
Check if there is voltage to the circulation
pump, if there is, and it does not run, the circu-
lation pump is jammed. If this is the case, open
the bleed screw and try to release the paddle
wheel using a screwdriver for example.
If there is no voltage to the circulation pump,
check if there is voltage from the control com-
puter, see wiring diagram. If there is voltage
from the control computer, check the com-
ponents between the control computer and
circulation pump.
If a component is defective, replace it.
Open closed main tap.
If a cable has come loose, connect it.
If there is a cable break, replace the cable.
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