Danfoss DHP-H Installation And Service Instructions Manual page 82

Cause
8. 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 refrig-
erant 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 pressure switch or delivery pipe
sensor.
10. Expansion valve defective or incorrectly
set.
11. Lack of refrigerant, not enough refriger-
ant in the system.
12. Overfilled refrigerant circuit.
13. Short active collector, e.g. short or dry
bore hole, short surface soil collector.
82
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 delivery 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 phas-
es 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 pres-
sure switch is open or the delivery pipe
sensor triggers an alarm for too high tem-
perature.
• The operating pressure switch is most eas-
ily 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
delivery pipe sensor and you have estab-
lished that it shows the correct tempera-
ture. This may have been caused by a leak
in the refrigerant circuit.
Using manometer apparatus and thermom-
eter 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.
Using manometer apparatus and thermom-
eter, check that the unit's overheating is
correct for the specific refrigerant.
Using manometer apparatus and thermom-
eter, check that the unit's overheating is
correct for the specific refrigerant.
• Check the length of the collector that is
being used and compare with the collector
length in the dimensioning documentation.
• In addition, check that the collector is
not suspended "in free air" if boreholes are
used.
VMBMA602
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.
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 persists,
replace the compressor.
If the overheating reading does not corre-
spond 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
expansion valve or if the capillary tube/bulb
is damaged, replace it.
Follow the correct procedure (depending
on type of refrigerant) to add the correct
amount of refrigerant.
If there appears to be a leak in the refriger-
ant circuit, carry out leak tracing and any
necessary corrective action. If leak tracer
is not available, brush soap water on the
suspected leak and look for bubbles. Also
check for oil as this can come out from the
refrigerant circuit.
If cooling is not at the correct level com-
pared with the specific refrigerant and is
too high, there is too much refrigerant
in the unit. Follow the correct procedure
(depending on type of refrigerant) to add
the correct amount of refrigerant.
If the active collector is too short, the heat
pump cannot receive enough energy from
the heat source, which results in it requiring
an addition to cover the energy require-
ment.