Danfoss DHP-AL Installation And Service Instructions Manual page 56

Cause
3. The compressor cannot run
due to an alarm.
4. The heat pump has stopped
on high return.
5. The compressor has been
stopped by the operating pres-
sure switch or delivery pipe
sensor.
6. The built-in overheating pro-
tection (bi-metal protection) in
the compressor has tripped.
7. The compressor runs back-
wards. 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 refriger-
ant and therefore does not pro-
duce the correct power, which
leads to the control computer
requesting auxiliary heating.
Problem – The heat pump consumes too much energy
Cause
1. Blocked strainer in the heat-
ing 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.
56
Troubleshooting
Check the alarm that is indicated in the display.
• Check what the MAX value is set at in the heat
pump's control computer. 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 temperature when the high-
est supply temperature is transmitted.
• 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.
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 "Measurement points" section.
• 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.
Check if the heat pump's control computer indi-
cates that the compressor is in operation, and if
there is voltage between soft-starters A1 and A2.
Then read off and check that there is voltage on
the compressor's three electrical connections (L1,
L2 and L3).
• 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 lit-
tle 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.
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 pipe 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 pipe 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.
Remedy
Rectify the problem and rest the alarm. See the
"Operational problem – Alarm" section.
• 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 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 there is voltage on the compressor's three elec-
trical connections and the overheating protection
does not close when the compressor has not run
and has cooled down for at least 1 hour, replace
the compressor.
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, system restric-
tions, system with high pressure drop.
VMBME102