Danfoss DHP-A Service Instructions Manual page 31

Service instructions
Problem – Auxiliary heater cuts in too soon
Cause
1. The heat pump's control comput-
er is not set/adjusted to the custom-
er'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
collector.
4. Collector too long, pressure drop
too great.
5. Changed conditions Have you in-
creased your heating and/or hot
water demand?
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
fitting system with poor pipe di-
mensions may produce the same
phenomena.
Problem – Connection of external AH
Cause
Incorrectly connected auxiliary
heater. Does not start when the
control computer gives the signal.
Danfoss Heating Solutions
Domestic heat pumps
Troubleshooting
Check the ROOM, CURVE, INTEGRAL A1 and INTE-
GRAL A2 settings
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.
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.
▪ 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 production
(only applies to system solution 1).
Troubleshooting
Check if the heat pumps starts, if the supply tem-
perature rises quickly whilst nothing 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 conditions 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.
Troubleshooting
Check the connection against the instructions/
wiring diagram. Test the function in manual mode.
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 tem-
perature. INTEGRAL A1 = Start value for the
compressor. INTEGRAL A2 = Start value
(calculated from A1) for the auxiliary heater.
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.
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 a longer collector is being used than rec-
ommended for the specific heat pump, it
must be divided on several parallel connec-
ted coils.
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.
Remedy
Adjust ROOM and CURVE if necessary. En-
sure that there is sufficient flow over the
condenser and the heating circuit.
Remedy
If the auxiliary heater is incorrectly connec-
ted, reconnect according to the instruc-
tions.
VIGFI102
31