Problem – Alarm Lp (Lower Pressure Transmitter); Problem – Alarm Hp (High Pressure Switch) - Danfoss DHP-AQ Mini Service Instructions Manual

3.5.1 Alarm
Table 6. Problem – Alarm LP (lower pressure transmitter)
Cause
1. Cable break or loose cable to lower
pressure transmitter.
2. The pressure transmitter opens too
soon.
3. Lack of refrigerant, not enough
refrigerant in the system.
4. Drying filter blockage.
5. Blocked evaporator on the refriger-
ant side.
Table 7. Problem – Alarm HP (high pressure switch)
Cause
1. Air in the heating system.
2. Blocked strainer in the heating sys-
tem.
3. Closed or partially closed thermo-
stats/valves in the heating system.
4. The circulation pump that is defec-
tive or has jammed.
Troubleshooting
•
Check that both cables are connected
to the lower pressure transmitter.
•
Using the buzzer, check that there are
no cable breaks. In order to do this,
disconnect the cables from the lower
pressure transmitter and circuit
board.
•
Pressure transmitter fault, opens at a
higher pressure than indicated. Check
break pressure using the manometer
apparatus.
Using manometer apparatus and ther-
mometer, check that the unit's overheat-
ing is correct for the specific refrigerant.
Check the temperature difference above
the drying filter. A difference of max 1°C is
permissible. If the difference is greater, the
filter is blocked. Take a reading during
operation.
Using manometer apparatus and ther-
mometer, check that the unit's overheat-
ing is correct for the specific refrigerant.
Troubleshooting
Listen for air in the heat pump and heat-
ing system.
Check that the strainer is not blocked.
Check that the thermostats/valves in the
heating system are open.
Is there voltage and 0 – 10V signal (applies
to A classed circulation pumps) up to the
circulation pump?
Remedy
If a cable has come loose, reconnect it.
If there is a cable break, replace the
cable.
If the pressure transmitter breaks too
early, replace it.
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.
If the drying filter is sealed, replace it.
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
Bleed the heating system according to
the installation instructions.
Clean the strainer if necessary.
Open closed thermostats/valves.
Check that the circulation pump is active
in the control system's manual test
menu.
Check if there is voltage to the circula-
tion pump, if there is, and it does not run,
the circulation pump is jammed. If this is
the case, open the bleed screw and try to
release the paddle wheel using a screw-
driver for example (Does not apply to
heat pumps in Opti).
If there is no voltage to the circulation
pump, check if there is voltage from the
I/O card, see wiring diagram. If there is
voltage from the I/O card, check the
components between the I/O card and
the circulation pump.
If a component is defective, replace it.
Service instructions VMGFJ102 – 15