Danfoss DHP-A Service Instructions Manual page 59

Cause
5. The heat pump's control computer
is not set/adjusted to the customer's
requirements/wishes.
6. The interval for peak heat opera-
tion has changed to a lower value
than the factory set value. This results
in the heat pump going into peak
heat operation more often than cal-
culated.
7. The heat pump has stopped on
HIGH RETURN.
8. The compressor runs backwards.
The incoming phases have the incor-
rect 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 cor-
rect power, which leads to the control
computer requesting auxiliary heat-
ing.
Troubleshooting
Check the ROOM and CURVE and MIN set-
tings.
Check the specified interval for peak heat
operation in the control computer, see
instructions for relevant model.
•
Check what the MAX RETURN value is
set at in the heat pump's control com-
puter. 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 tem-
perature 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 Mätpunkter.
•
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 incorrectly sequenced a
strange noise may be heard (loud, rat-
tling) when the compressor runs back-
wards.
Remedy
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 temperature.
MIN = Lowest set-point value on the
supply line regardless of the outdoor
temperature.
If there is a shorter interval between the
peak heat productions, this explains why
the unit consumes more current than
calculated, but this does not mean for
sure that it should be increased, there
might be a reason why the interval has
been changed.
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.
If the phases are in the incorrect order,
switch two incoming phases at the main
terminal block and recheck according to
the troubleshooting window.
Service instructions VMGFC302 – 57