Danfoss DHP-A Service Instructions Manual page 30

Service instructions
Cause
9. The compressor has been stop-
ped by the operating pressure
switch or delivery line sensor.
10. Expansion valve defective or in-
correctly 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
collector.
14. Changed conditions Have you
increased your heating and/or hot
water demand?
30
Domestic heat pumps
Troubleshooting
Check if a square appears in the display's lower left
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 con-
nected.
▪ 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 installation
instructions.
▪ The compressor has been stopped by the de-
livery line sensor and you have established
that it shows the correct temperature. This
may have been caused by a leak in the refrig-
erant circuit.
Using manometer apparatus and thermometer
check what the overheating reading of the unit is.
Also check that bulb and capillary tube are undam-
aged and that the bulb is correctly installed.
Using manometer apparatus and thermometer,
check that the unit's overheating is correct for the
specific refrigerant.
Using manometer apparatus and thermometer,
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 sus-
pended "in free air" if boreholes are used.
▪ If the heat pump has been dimensioned 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 wa-
ter, which means less time for heat produc-
tion.
VIGFI102
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 re-
peatedly, replace the pressure switch. If the
delivery line sensor 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 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 over-
heating cannot be adjusted with the ex-
pansion valve or if the capillary tube/bulb is
damaged, replace it.
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 sus-
pected leak and look for bubbles. Also
check for oil as this can come out from the
refrigerant circuit.
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 requir-
ing an addition to cover the energy require-
ment.
If the heat pump cannot cope with the de-
mand, replace it with one with a higher
output or supplement it with a higher out-
put auxiliary heater.
Danfoss Heating Solutions