Danfoss DHP-A Service Instructions Manual page 40

Cause
6. The low pressure switch opens too
soon.
7. Incorrect type of anti-freeze, must
be in accordance with instructions.
8. Incorrect mix of anti-freeze, the
concentration must be in accordance
with instructions.
9. Short active collector, e.g. short or
dry bore hole, short surface soil collec-
tor.
10. Collector too long, pressure drop
too great.
11. Expansion valve defective or incor-
rectly set.
12. Lack of refrigerant, not enough
refrigerant in the system.
13. Drying filter blockage.
38 – Service instructions VMGFC302
Troubleshooting
•
Incorrect pressure switch installed.
Higher break pressure than intended.
See marking.
•
Pressure switch fault, opens at a
higher pressure than indicated (mark
pressure). Check using the manome-
ter apparatus.
•
Defective pressure switch, always
open.
Check that the correct type of anti-freeze
is used.
Check the freezing point of the mix using
a refractometer.
•
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 bore-
holes are used.
Check the length of the collector that is
being used and that it is connected in par-
allel (not connected in series) if more than
1 coil is being used.
•
Using manometer apparatus and
thermometer check what the over-
heating 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 ther-
mometer, check that the unit's overheat-
ing is correct for the specific refrigerant.
Check the temperature difference above
the drying filter. A one degree difference is
permissible. If the difference is greater
than 1 degree, the filter is blocked. Take a
reading during operation.
Remedy
If the low pressure switch opens too
soon or is always open, replace it.
If the incorrect type of anti-freeze is used,
the entire system must be drained and
refilled with a new mixture.
If the mixture is not in accordance with
the instructions, it must be remixed in an
external container. This is because the
fluids do not mix with each other well if
one is filled directly into the system.
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 a longer collector is being used than
recommended for the specific heat
pump, it must be divided on several par-
allel connected coils.
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.
Follow the correct procedure (depend-
ing on type of refrigerant) to add the cor-
rect amount of refrigerant.
If there appears to be a leak in the refrig-
erant circuit, carry out leak tracing and
any necessary corrective action.
If the drying filter is sealed, replace it.