Cause
Troubleshooting
Remedy
5. The compressor has been
stopped by the operating
pressure switch or delivery
line sensor.
Check if a square appears in the display’s lower left corner.
If so, the operating pressure switch is open or the delivery
pipe sensor triggers an alarm for too high temperature.
▪
The operating pressure switch is most easily checked
by using a buzzer to see if it is connected.
▪
The pressure pipe sensor value is read off from the
control system in the HEAT PUMP menu. Is it a plausi-
ble/actual value? If not, take a resistance reading from
the sensor and check against the ohm table in Meas-
▪
The compressor has been stopped by the delivery line
sensor and you have established that it shows the
correct temperature. This may have been caused by a
leak in the refrigerant circuit.
If the operating pressure switch has stuck in
the open position, try gently tapping on
the pressure switch head. If this does not
help, or it sticks in the open position re-
peatedly, replace the pressure switch. If the
delivery line sensor is defective, replace it. If
the delivery line temperature gets so hot
that the compressor stops, start by leak-
tracing the unit. Rectify the leak, if a leak is
found. If no leak is found, try draining and
refilling the unit and then restarting the
heat pump and seeing what the delivery
line temperature is. If the problem persists,
replace the compressor.
6. The compressor runs
backwards. The incoming
phases have the incorrect
sequence (only applies to 3-
phase heat pumps). If the
compressor runs backwards,
it will not cope with com-
pressing the refrigerant and
therefore does not produce
the correct power, which
leads to the control system
requesting auxiliary heating.
▪
If the text ERR PHASE SEQ. appears in the display
when the heat pump is powered, (only appears in the
first 10 minutes) this means that the phases have the
incorrect sequence.
▪
When the compressor is running, check the pressure
pipe temperature by feeling the pressure pipe. If the
phases are correctly sequenced it should be hot (not
just warm) even a distance from the compressor.
▪
When the compressor runs with the phases incorrect-
ly sequenced a strange noise may be heard (loud, rat-
tling) when the compressor runs backwards.
If the phases are in the incorrect order,
switch two incoming phases at the main
terminal block and recheck according to
the troubleshooting window.
7. The built-in overheating
protection (bi-metal protec-
tion) in the compressor has
tripped.
Check if the heat pump’s control computer indicates that
the compressor is in operation, and if there is voltage in
the soft-starter control inputs. Then read off and check
that there is voltage on the compressor’s electrical connec-
tion(s).
If there is voltage on the compressor’s elec-
trical connection(s) and the overheating
protection does not close when the com-
pressor has not run and has cooled down
for at least 1 hour, replace the compressor.
Problem – The heat pump consumes too much energy
Cause
Troubleshooting
Remedy
1. Blocked strainer in the
heating system.
Check that the strainer is not blocked.
Clean the strainer if necessary.
2. The compressor cannot
run due to an alarm.
Check the alarm that is indicated in the display.
Rectify the problem and rest the alarm. See
3. Incorrect flow over hot
side of the heat pump.
Measurement check what the difference between the sup-
ply and return line is using a thermometer (∆t). The differ-
ence should be about 8°C (can vary depending on refriger-
ant). A lower ∆t results in reduced efficiency in the heat
pump.
Adjust the system to obtain the correct ∆t.
4. The heat pump’s control
computer is not set/adjus-
ted to the customer’s re-
quirements/wishes.
Check the ROOM and CURVE and MIN settings.
Adjust incorrect values in the heat pump’s
control computer. ROOM = Desired indoor
temperature CURVE = Should be set so that
the desired indoor temperature (ROOM) is
maintained regardless of the outdoor tem-
perature. MIN = Lowest set-point value on
the supply line regardless of the outdoor
temperature.
Service Instructions
DHP-AQ
VMGFJ202
Danfoss Heating Solutions
30
