Danfoss DHP-A Service Instructions Manual page 28

Service instructions
Cause
4. The heat pump has stopped on
high return.
5. The compressor has been stop-
ped by the operating pressure
switch or delivery line sensor.
6. The built-in overheating protec-
tion (bi-metal protection) in the
compressor has tripped.
7. The compressor runs backwards.
The incoming phases have the in-
correct sequence (only applies to 3-
phase heat pumps). If the compres-
sor runs backwards, it will not cope
with compressing the refrigerant
and therefore does not produce the
correct power, which leads to the
control system requesting auxiliary
heating.
Problem – The heat pump consumes too much energy
Cause
1. Blocked strainer in the heating
system.
2. The compressor cannot run due
to an alarm.
28
Domestic heat pumps
Troubleshooting
▪ Check what the MAX value is set at in the heat
pump's control computer. It must be adjusted
to the unit's maximum supply temperature
and the system's delta temperature so that it
does not cut at too high a return temperature
when the highest supply temperature is trans-
mitted.
▪ Check what the return line sensor shows. Is it
a plausible/actual value? If not, take a resist-
ance reading from the sensors and check
against the ohm table, see chapter Measure-
ment points.
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 con-
nected.
▪ The pressure pipe sensor value is read off from
the control system in the HEAT PUMP menu. Is
it a plausible/actual value? If not, take a resist-
ance reading from the sensor and check
against the ohm table, see chapter Measure-
ment points.
▪ The compressor has been stopped by the de-
livery line sensor and you have established
that it shows the correct temperature. This
may have been caused by a leak in the refrig-
erant circuit.
Check if the heat pump's control computer indi-
cates 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 connection(s).
▪ If the text ERR PHASE SEQ. appears in the dis-
play 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 se-
quenced it should be hot (not just warm) even
a distance from the compressor.
▪ When the compressor runs with the phases in-
correctly sequenced a strange noise may be
heard (loud, rattling) when the compressor
runs backwards.
Troubleshooting
Check that the strainer is not blocked.
Check the alarm that is indicated in the display.
VIGFI102
Remedy
▪ If the MAX RETURN value is not adjus-
ted for the system according to the
troubleshooting window, adjust it.
▪ If the sensor is defective, replace it.
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.
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.
If the phases are in the incorrect order,
switch two incoming phases at the main
terminal block and recheck according to
the troubleshooting window.
Remedy
Clean the strainer if necessary.
Rectify the problem and rest the alarm. See
the Operational problem – Alarm.
Danfoss Heating Solutions