Danfoss DHP-A Service Instructions Manual page 54

Cause
9. The external auxiliary heater does not
start when the heat pump's control
computer requests it.
10. Closed or partially closed thermo-
stats/valves in the heating system.
11. The total output of the heat pump
and auxiliary heater is too low in relation
to the building's power demand.
12. Under dimensioned heating system.
13. Changed conditions
Have you increased your heating and/or
hot water demand?
Table 31. Problem – Too hot
Cause
1. The heat pump's control computer is
not set/adjusted to the customer's
requirements/wishes.
2. Sensor fault, OUTDOOR/ROOM/SUP-
PLY LINE.
52 – Service instructions VMGFC302
Troubleshooting
If an external auxiliary heater is used,
check that it is correctly installed by test
running it in MANUAL TEST – AUX.
HEATER - 1.
If it does not start at manual test opera-
tion, check that the start signal/voltage
comes from the heat pump. See wiring
diagram.
Check that the thermostats/valves in the
heating system are open.
What is the building's power demand?
What is the output of the heat pump?
What is the output of the auxiliary
heater, what is it set to?
Check existing heating system.
What output is it dimensioned for to
produce at what supply temperature?
What output is required to keep the
room warm?
•
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 main-
tain 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 the ROOM and CURVE and MIN set-
tings.
Check what the relevant sensor shows. Is
it a plausible/actual value?
Measure the resistance of the sensor,
check against the ohm table in Measure-
ment points.
Remedy
Connect the external auxiliary heater
according to the instructions.
Measure the voltage on the I/O card's
probe L2 Oil/Electricity.
Open closed thermostats/valves.
Ensure that available power is at least as
great as the building's power demand.
If the heating system is dimensioned for
greater supply temperatures than the
heat pump can provide, it must be
adjusted by increasing the heat emitting
surface for example.
If the room requires a higher output
than the heating system can provide,
extend the heating system.
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 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.
MIN = Lowest set-point value on the
supply line regardless of the outdoor
temperature.
If the sensor is defective, replace it.