Danfoss DHP-AX Installation And Service Instructions Manual page 63

Cause
7. 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 system
requesting auxiliary heating.
Problem – The heat pump consumes too much energy
Cause
1. Blocked strainer in the heating
system.
2. The compressor cannot run due
to an alarm.
3. Incorrect flow over hot side of
the heat pump.
4. Incorrect flow in the brine circuit.
5. The heat pump's control com-
puter 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 calculated.
Troubleshooting
• 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 cor-
rectly sequenced it should be hot (not just
warm) even a distance from the compres-
sor .
• When the compressor runs with the pha-
ses incorrectly sequenced a strange noise
may be heard (loud, rattling) when the
compressor runs backwards.
Troubleshooting
Check that the strainer is not blocked.
Check the alarm that is indicated in the
display.
Measurement check what the difference
between the 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 set-
tings.
Check the specified interval for peak heat
operation in the control computer, see
instructions for relevant model.
VMBMH302
Remedy
If the phases are in the incorrect order,
switch two incoming phases at the main
terminal block and recheck according to
the troubleshooting window.
Remedy
Clean the strainer if necessary.
Rectify the problem and rest the alarm. See
the Operational problem – Alarm, section.
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 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 calcula-
ted, but this does not mean for sure that it
should be increased, there might be a rea-
son why the interval has been changed.
Service – 63