Danfoss DHP-AL Installation And Service Instructions Manual page 57

Cause
5. The heat pump's control
computer is not set/adjusted to
the customer's requirements/
wishes.
6. The interval for peak heat
operation 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.
7. The heat pump has stopped
on HIGH RETURN.
8. The compressor runs back-
wards. Incoming phases are in
the incorrect order. If the com-
pressor 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 auxiliary
heating.
9. The compressor has been
stopped by the operating pres-
sure switch or delivery pipe
sensor.
10. Expansion valve defective
or incorrectly set.
Troubleshooting
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 tempera-
ture and the system's delta temperature so that
it does not cut at too high a return temperature
when the highest supply temperature is transmit-
ted.
• Check what the return pipe 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 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 deliv-
ery pipe temperature by feeling the delivery pipe
that should be hot (not just warm) even a little
distance from the compressor if the phases are
correctly sequenced.
• When the compressor runs with the phases
incorrectly sequenced a strange noise may be
heard (loud, rattling) when the compressor runs
backwards.
Check if a square appears in the display's lower let
corner, if so, the operating pressure switch is open
or the delivery pipe sensor triggers an alarm for
too high temperature.
• The operating pressure switch is most easily
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 installation instructions.
• The compressor has been stopped by the deliv-
ery pipe sensor and you have established that
it shows the correct temperature. This may have
been caused by a leak in the refrigerant circuit.
Using manometer apparatus and thermometer
check what the overheating reading of the unit is.
Also check that bulb and capillary tube are
undamaged and that the bulb is correctly
installed.
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 pipe
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 troubleshooting 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.
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 per-
sists, replace the compressor.
If the overheating reading does not correspond
with the instructions for the specific refrigerant,
adjust the expansion valve until the correct value
is obtained. See separate instructions for cooling
techniques.
If overheating cannot be adjusted with the expan-
sion valve or if the capillary tube/bulb is dam-
aged, replace it.
VMBME102
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