Danfoss DHP-AX Installation And Service Instructions Manual page 62

Problem – The auxiliary heater is in operation but not the compressor
Cause
1. Operating mode AUX. HEATER
is selected.
2. Peak heat operation (anti-legio-
nella function) is running.
3. The compressor cannot run due
to an alarm.
4. The heat pump has stopped on
high return.
5. The compressor has been stop-
ped by the operating pressure
switch or pressure pipe sensor.
6. The built-in overheating protec-
tion (bi-metal protection) in the
compressor has tripped.
62 – Service
Troubleshooting
If this operating mode is selected, the
auxiliary heater is used for heating and hot
water production, not the compressor.
Check if the heat pump runs peak heat. See
the instructions for the relevant model.
Check the alarm that is indicated in the
display.
• 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
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.
Check if a square appears in the display's
lower let corner, if so, the operating pres-
sure switch is open or the pressure pipe
sensor triggers an alarm for too high tem-
perature.
• 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 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
pressure pipe sensor and you have establis-
hed that it shows the correct temperature.
This may have been caused by a leak in the
refrigerant circuit.
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).
VMBMH302
Remedy
If AUX. HEATER mode is selected and you
no longer want it, change to AUTO, the
heat pump then controls both the com-
pressor and auxiliary heater.
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.
Rectify the problem and rest the alarm. See
the Operational problem – Alarm, section.
• If the MAX RETURN value is not adjusted
for the system according to the trou-
bleshooting 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 repea-
tedly, replace the pressure switch.
If the pressure pipe sensor is defective,
replace it.
If the pressure 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 pressure pipe temperature is. If the pro-
blem persists, replace the compressor.
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.