Danfoss DHP-A Service Instructions Manual page 29

Service instructions
Cause
3. Incorrect flow over hot side of the
heat pump.
4. Incorrect flow in the brine circuit.
5. The heat pump's control comput-
er is not set/adjusted to the custom-
er's requirements/wishes.
6. The interval for peak heat opera-
tion has changed to a lower value
than the factory set value. This re-
sults in the heat pump going into
peak heat operation more often
than calculated.
7. The heat pump has stopped on
HIGH RETURN.
8. 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 computer requesting auxili-
ary heating.
Danfoss Heating Solutions
Domestic heat pumps
Troubleshooting
Measurement check what the difference between
the heat pump supply and return line is using a
thermometer (∆t). The difference should be about
7-10°C (can vary depending on refrigerant). A lower
∆t results in reduced efficiency in the heat pump.
Measurement check what the difference between
the supply and return line is using a thermometer
(∆t). The difference should not be more than 4°C. A
greater ∆t results in reduced efficiency in the heat
pump.
Check the ROOM and CURVE and MIN settings.
Check the specified interval for peak heat opera-
tion in the control computer, see instructions for
relevant model.
▪ 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 tem-
perature and the system's delta temperature
so that it does not cut at too high a return
temperature when the highest supply tem-
perature is transmitted.
▪ 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.
▪ 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.
Remedy
Adjust the system to obtain the correct ∆t.
If the difference is greater than 4°C note
what is causing it. E.G.: Dirt in the filter, sys-
tem restrictions, system with high pressure
drop.
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 tem-
perature. 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 calcu-
lated, 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 troubleshoot-
ing window, adjust it. If the sensor is defec-
tive, 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.
VIGFI102
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