Danfoss DHP-A Service Instructions Manual page 61

Table 37. Problem – Auxiliary heater cuts in too soon
Cause
1. The heat pump's control computer
is not set/adjusted to the customer's
requirements/wishes.
2. Lack of refrigerant, not enough
refrigerant in the system.
3. Short active collector, e.g. short or
dry bore hole, short surface soil col-
lector.
4. Collector too long, pressure drop
too great.
5. Changed conditions Have you
increased your heating and/or hot
water demand?
Table 38. Problem – Short operating times despite heating demand
Cause
ROOM and/or CURVE set too high in
combination with a heating system
with poor circulation due to closed
radiator valves, too small elements or
insufficient water volume. A tight fit-
ting system with poor pipe dimen-
sions may produce the same phe-
nomena.
Troubleshooting
Check the ROOM, CURVE, INTEGRAL A1 and
INTEGRAL A2 settings
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.
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.
•
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 (only applies
to system solution 1).
Troubleshooting
Check if the heat pumps starts, if the sup-
ply temperature rises quickly whilst noth-
ing happens to the return temperature. If
this happens and the heat pump is stopped
by the hysteresis function to later quickly
drop in temperature (supply) in order to
start again, but cannot due to time condi-
tions in regulation, this means that the heat
pump cannot transport the heat away from
the condenser as it should. In such a case,
hysteresis starts and stops the heat pump
often.
Remedy
Adjust incorrect values in the heat
pump's control computer. ROOM =
Desired indoor temperature CURVE =
Should be set so that the desired indoor
temperature (ROOM) is maintained
regardless of the outdoor temperature.
INTEGRAL A1 = Start value for the com-
pressor. INTEGRAL A2 = Start value (cal-
culated from A1) for the auxiliary heater.
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.
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 heat pump cannot cope with the
demand, replace it with one with a
higher output or supplement it with a
higher output auxiliary heater.
Remedy
Adjust ROOM and CURVE if necessary.
Ensure that there is sufficient flow over
the condenser and the heating circuit.
Service instructions VMGFC302 – 59