Danfoss DHP-H, Installation And Service Instructions Manual

Page: 79 / 96

79
VMBMA602
Problem – Runs on electric heating element
Cause Troubleshooting Remedy
1. Operating mode ADD.HEAT is selected. If this operating mode is selected, the aux-
iliary heater is used for heating and hot
water production, not the compressor.
If ADD.HEAT mode is selected and you no
longer want it, change to AUTO, the heat
pump then controls both the compressor
and auxiliary heater.
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
the Operational problem – Alarm, section.
3. The integral value has reached the start
level for the auxiliary heater.
Check what the integral value is in the con-
trol computer.
If the auxiliary heater is in operation
because the integral value has counted
down to the start value, the computer
reacts as it should, see the Heat pump for
further information.
4. Peak heat operation (legionella function)
is running.
Check if the heat pump runs peak heat. See
the instructions for the relevant model.
Peak heat operation occurs in connection
with hot water production with the set
interval. The compressor should then start
to produce hot water and 2 minutes later
the auxiliary heater starts, the compressor
should then stop and the stop temperature
is reached with only the auxiliary heater
connected. Take no corrective action.
5. The heat pump has stopped on HIGH
RETURN.
• Check what the MAX RETURN 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 transmitted.
• Check what the return line sensor shows,
is it a plausible/actual value? If not, take
a resistance reading from the sensors
and check against the ohm table in the
Measurement points section.
If the MAX RETURN value is not adjusted for
the system according to the troubleshoot-
ing window, adjust it.
If the sensor is defective, replace it.
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 compressing the refrigerant
and therefore does not produce the correct
power, which leads to the control computer
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 delivery pipe temperature by feeling
the delivery pipe that should be hot (not
just warm) even a little distance from the
compressor if the phases are correctly
sequenced.
• When the compressor runs with the phas -
es incorrectly sequenced a strange noise
may be heard (loud, rattling) 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. Changed conditions. Have you increased
your heating and/or hot water demand?
• If the heat pump has been dimensioned
for a certain demand and this demand is
increased, the heat pump might not be able
to maintain the desired room temperature.
• If hot water consumption increases, a
larger proportion of time is used to produce
hot water, which means less time for heat
production (only applies to VL-systems).
If the heat pump cannot cope with the
demand, replace it with one with a higher
output or supplement it with a higher out-
put auxiliary heater.