Danfoss DHP-A Service Instructions Manual page 53

Cause
4. The 3-way valve has jammed in hot
water mode.
5. Defective electric heating element.
6. The heat pump has stopped on HIGH
RETURN.
7. Heat production is stopped by the
HYSTERESIS function.
8. The auxiliary heater is not permitted
to cut in with sufficient output.
Value set too low on MAXSTEP.
MAXSTEP 1 = 3 kW
MAXSTEP 2 = 6 kW
MAXSTEP 3 = 9 kW
MAX STEP 4 = 12 kW (only DHP A)
MAX STEP 5 = 15 kW (only DHP A)
MAX STEP +4 = 12 kW (only DHP A)
MAX STEP +5 = 15 kW (only DHP A)
Troubleshooting
1. Check the function of the 3-way
valve motor by test running it
manually. If the motor does not
shift mode during manual test
operation, check that there is
voltage to the motor, see wiring
diagram.
2. Detach the motor and test clos-
ing and opening of the valve by
pressing the control arm.
Use a buzzer and check if all coils in the
electric heating element are intact.
•
Check what the MAX RETURN value
is set at in the heat pump's control
computer. It must be adjusted to
the unit's maximum supply temper-
ature and the system's delta tem-
perature so that it does not cut at
too high a return temperature
when the highest supply tempera-
ture 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 the Measurement
points section 19.3.
If the flow temperature rises as soon as
heat production is stopped by HYSTERE-
SIS 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 parti-
ally closed?
•
Check if heat production stops
because the heating system is
under dimensioned?
Check the set value on MAXSTEP in the
heat pump's control computer.
Remedy
1. Is the motor being supplied with
voltage according to the wiring
diagram in both operating
instances?
MANUAL TEST – REV.V. HOT
WATER 0=Radiator mode, arm
out from valve. 1=Hot water
mode, arm positioned towards
the valve.
If there is voltage to the motor
but the arm does not shift mode,
replace it.
2. Take out and clean the jammed
insert, or replace with a new
insert.
If the electric heating element is defec-
tive, replace it.
If the MAX RETURN value is not adjusted
for the system according to the trouble-
shooting window, adjust it.
If the sensor is defective, replace it.
•
Try increasing the hysteresis value
until the heat pump stops on INTE-
GRAL instead.
•
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 (the heat emit-
ting surface increased).
If necessary, adjust the MAXSTEP value
in the heat pump's control computer.
MAXSTEP 1 = 3 kW
MAXSTEP 2 = 6 kW
MAXSTEP 3 = 9 kW
MAX STEP 4 = 12 kW (only DHP A, can-
not cut in when the compressor is run-
ning.)
MAX STEP 5 = 15 kW (only DHP A, can-
not cut in when the compressor is run-
ning.)
MAX STEP +4 = 12 kW (only DHP A, can
cut in when the compressor is running.)
MAX STEP +5 = 15 kW (only DHP A, can
cut in when the compressor is running.)
Service instructions VMGFC302 – 51