Danfoss DHP-A Service Instructions Manual page 45

Table 18. Problem – Alarm AH (auxiliary heat)
Cause
1. The overheating protection has trip-
ped.
2. Phase drop.
The alarm occurs when 230 V is not
registered between L2 on the circuit
board and N.
3. Overheating protection fault, cannot
be reset.
4. Flow sensor fault.
5. No or insufficient circulation in the
heating system.
6. The submersible tube in the electric
heating element is against the coils.
Table 19. Problem – Alarm Brine out
Cause
1. Defective sensor.
2. Brine temperature too low.
Troubleshooting
Check if the overheating protection has
tripped.
•
Check if the overheating protection
has tripped.
•
Check if any cables at the circuit
board or overheating protection are
loose or damaged.
Press the reset button, measurement
check for 230 V on the incoming and out-
going connections.
Check what the flow sensor shows. Is it a
plausible/actual value?
Measure the resistance of the sensor,
check against the ohm table in Measure-
ment points.
Check:
•
That the circulation pump spins
•
That the shut-off valves are open.
•
That the strainer is not blocked.
•
That there is no air in the heating sys-
tem.
Check what the flow temperature is when
the overheating protection trips.
This normally trips at 95°C.
Troubleshooting
Check what the sensor shows. Is it a plau-
sible/actual value?
Measure the resistance of the sensor,
check against the ohm table in Measure-
ment points.
Check the set value on ALARM BRINE in
the heat pump's control computer.
Remedy
If the overheating protection has trip-
ped, reset it.
If the overheating protection has trip-
ped, reset it.
If the cables are loose or damaged,
secure or replace them.
If the overheating protection is defec-
tive, replace it.
If the sensor is defective, replace it.
The circulation pump may have jam-
med. If so, open the bleed screw and try
to release the paddle wheel using a
screwdriver for example.
Open closed valves or taps.
Check, and, if necessary, clean the
strainer.
If necessary, bleed the heating system
according to the installation instructions
The submersible tube can be prised out
slightly from the coils using a screw-
driver or similar. The submersible tube
must be vertical.
Remedy
If the sensor is defective, replace it.
The alarm is triggered when the temper-
ature on BRINE OUT is as low or lower
than the set value on ALARM BRINE. In
the factory setting this function is inac-
tive.
Service instructions VMGFC302 – 43