Danfoss DHP-AX Installation And Service Instructions Manual page 47

Cause
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 sur-
face soil collector.
10. Collector too long, pressure
drop too great.
11. Expansion valve defective or
incorrectly set.
12. Lack of refrigerant, not
enough refrigerant in the system.
13. Drying filter blockage.
14. Blocked evaporator on the
water side.
Troubleshooting
Check the freezing point of the mix using
a refractometer.
• Check the length of the collector that
is being used and compare with the col-
lector length in the dimensioning docu-
mentation.
• In addition, check that the collector is
not suspended "in free air" if boreholes
are used.
Check the length of the collector that is
being used and that it is connected in
parallel (not connected in series) if more
than 1 coil is being used.
Using manometer apparatus and ther-
mometer check what the overheating
reading of the unit is.
Also check that bulb and capillary tube
are undamaged and that the bulb is cor-
rectly installed.
Using manometer apparatus and ther-
mometer, check that the unit's overhea-
ting is correct for the specific refrigerant.
Check the temperature difference above
the drying filer. A one degree difference
is permissible. If the difference is greater
than 1 degree, the filter is blocked. Take a
reading during operation.
If there is no strainer in the brine circuit,
there is a risk of dirt sticking in the eva-
porator and blocking it. Unfortunately
there is no easy way of checking if the
evaporator is blocked.
You can carry out a test by allowing
the compressor and circulation pumps
to remain in operation. Check that the
circulation pumps work (for circ.pumps
with a bleed screw, unscrew it and feel
if the pump rotor rotates using a screw-
driver).
Then read the temperature on both con-
nection pipes to the evaporator:
If the temperature difference is <1°C, the
evaporator is probably blocked.
If the temperature difference is 2-6°C, it is
probably not blocked.
If the temperature difference is >6°C, the
evaporator is probably blocked.
VMBMH302
Remedy
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 ener-
gy 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
parallel 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 (depending
on type of refrigerant) to add the correct
amount of refrigerant.
If there appears to be a leak in the refri-
gerant circuit, carry out leak tracing and
any necessary corrective action.
If the drying filter is sealed, replace it.
If the evaporator is thought to be block-
ed, try flushing it. If this does not work, it
must be replaced.
Service – 47