Danfoss DHP-AX Installation And Service Instructions Manual page 58

Cause
6. The heat pump has stopped
on HIGH RETURN.
7. Heat production is stopped by
the HYSTERESIS function.
8. The external auxiliary hea-
ter does not start when the
heat pump's control computer
requests it.
9. Closed or partially closed ther-
mostats/valves in the heating
system.
10. The total output of the heat
pump and auxiliary heater is too
low in relation to the building's
power demand.
11. Under dimensioned heating
system.
58 – Service
Troubleshooting
• Check what the MAX RETURN value is
set at in the heat pump's control com-
puter. It must be adjusted to the unit's
maximum supply temperature and the
system's delta temperature so that it does
not cut at too high a return temperature
when the highest supply temperature is
transmitted.
• Check what the return line sensor
shows, is it a plausible/actual value? If
not, take a resistance reading from the
sensors and check against the ohm table
in section 15.3 Measurement points.
If the flow temperature rises as soon
as heat production is stopped by
HYSTERESIS before INTEGRAL reaches
0, there may be heating deficit in the
house.
• Check if heat production stops because
the hysteresis value is set too low? (See
the installation instructions for factory
setting.)
• Check if heat production stops because
thermostats/valves in the heating system
are closed or partially closed?
• Check if heat production stops because
the heating system is under dimensio-
ned?
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 pro-
duce at what supply temperature?
What output is required to keep the
room warm?
VMBMH302
Remedy
If the MAX RETURN value is not adjusted
for the system according to the trou-
bleshooting window, adjust it.
If the sensor is defective, replace it.
• Try increasing the hysteresis value until
the heat pump stops on INTEGRAL ins-
tead.
• Open thermostats/valves in the heating
system and check that the heat pump
stops on INTEGRAL.
• If the heating system is deemed to be
under dimensioned, the system must
be extended (increase the heat emitting
surface).
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.