Danfoss DHP-A Service Instructions Manual page 60

Cause
9. The compressor has been stopped
by the operating pressure switch or
delivery line sensor.
10. Expansion valve defective or
incorrectly set.
11. Lack of refrigerant, not enough
refrigerant in the system.
12. Overfilled refrigerant circuit.
13. Short active collector, e.g. short or
dry bore hole, short surface soil col-
lector.
14. Changed conditions Have you
increased your heating and/or hot
water demand?
58 – Service instructions VMGFC302
Troubleshooting
Check if a square appears in the display's
lower left 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
easily checked by using a buzzer to see
if it is connected.
•
The delivery line sensor value is read
off from the control computer in the
HEAT PUMP menu. Is it a plausible/
actual value? If not, take a resistance
reading from the sensor and check
against the ohm table in the installa-
tion instructions.
•
The compressor has been stopped by
the delivery line sensor and you have
established that it shows the correct
temperature. This may have been
caused by a leak in the refrigerant cir-
cuit.
Using manometer apparatus and ther-
mometer check what the overheating read-
ing of the unit is. Also check that bulb and
capillary tube are undamaged and that the
bulb is correctly installed.
Using manometer apparatus and ther-
mometer, check that the unit's overheating
is correct for the specific refrigerant.
Using manometer apparatus and ther-
mometer, 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.
•
If the heat pump has been dimen-
sioned for a certain demand and this
demand is increased, the heat pump
might not be able to maintain the
desired room temperature.
•
If hot water consumption increases, a
larger proportion of time is used to
produce hot water, which means less
time for heat production.
Remedy
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 line sen-
sor is defective, replace it. If the delivery
line 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 line temperature is. If the prob-
lem persists, replace the compressor.
If the overheating reading does not cor-
respond 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.
If there appears to be a leak in the refrig-
erant 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 bub-
bles. Also check for oil as this can come
out from the refrigerant circuit.
Follow the correct procedure (depend-
ing 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 requirement.
If the heat pump cannot cope with the
demand, replace it with one with a
higher output or supplement it with a
higher output auxiliary heater.