Danfoss DHP-H, Installation And Service Instructions Manual

Page: 80 / 96

80
VMBMA602
Problem – The auxiliary heater is in operation but not the compressor
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. 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, this is
normal.
3. 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.
4. The heat pump has stopped on high
return.
• 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 tem-
perature so that it does not cut at too high
a return temperature when the highest sup-
ply 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 trouble-
shooting window, adjust it.
• If the sensor is defective, replace it.
5. The compressor has been stopped by the
operating pressure switch or delivery pipe
sensor.
Check if a square appears in the display’s
lower let corner, if so, the operating pres-
sure switch is open or the delivery pipe
sensor triggers an alarm for too high tem-
perature.
• The operating pressure switch is most eas -
ily checked by using a buzzer to see if it is
connected.
• The delivery pipe sensor value is read
off from the control computer in the
HEATPUMP menu. Is it a plausible/actual
value? If not, take a resistance reading from
the sensor and check against the ohm table
in the Measurement points section.
• The compressor has been stopped by the
delivery pipe sensor and you have estab-
lished that it shows the correct tempera-
ture. 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 repeatedly,
replace the pressure switch.
If the delivery pipe sensor is defective,
replace it.
If the delivery pipe 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
pipe temperature is. If the problem persists,
replace the compressor.
6. The built-in overheating protection (bi-
metal protection) in the compressor has
tripped.
Check if the heat pump’s control computer
indicates that the compressor is in opera-
tion, and if there is voltage between soft-
starters A1 and A2. Then read off and check
that there is voltage on the compressor’s
three electrical connections (L1, L2 and L3).
If there is voltage on the compressor’s three
electrical connections 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.