Danfoss DHP-A Service Instructions Manual page 11

Service instructions
Problem – Alarm HP (high pressure switch)
Cause
1. Blocked strainer in the heating
system.
2. Air in the heating system.
3. Closed or partially closed thermo-
stats/valves in the heating system.
4. The circulation pump that is de-
fective or has jammed.
5. Shut-off main tap in heating sys-
tem.
6. Cable break or loose cable to high
pressure switch.
7. The high pressure switch does
not open.
8. The high pressure switch opens
too soon.
9. External system shunt that closes
on time setting.
Danfoss Heating Solutions
Domestic heat pumps
Troubleshooting
Check that the strainer is not blocked.
Listen for air in the heat pump and heating system. Bleed the heating system according to the
Check that the thermostats/valves in the heating
system are open.
Is there voltage to the circulation pump?
Check that the main tap is open.
▪ Check that both cables are connected to the
pressure switch.
▪ Using the buzzer, check that there are no ca-
ble breaks. In order to do this, disconnect the
cables from the pressure switch and circuit
board.
▪ Incorrect pressure switch installed. Same or
higher break pressure than the high pressure
switch. See marking.
▪ Pressure switch fault, opens at a higher pres-
sure than indicated (mark pressure). Check us-
ing the manometer apparatus.
▪ Defective pressure switch, never opens.
▪ Incorrect pressure switch installed. As low or
lower break pressure than operating pressure
switch. See marking.
▪ Pressure switch fault, opens at a lower pres-
sure than indicated (mark pressure). Check us-
ing the manometer apparatus.
▪ Defective pressure switch, always open.
Check for shunts or valves in the system, which are
timer-controlled, that close down the entire or too
large a part of the heating system.
Remedy
Clean the strainer if necessary.
installation instructions.
Open closed thermostats/valves.
Check that the circulation pump is active in
the control system's manual test menu.
Check if there is voltage to the circulation
pump, if there is, and it does not run, the
circulation pump is jammed. If this is the
case, open the bleed screw and try to re-
lease the paddle wheel using a screwdriver
for example (Does not apply to speed con-
trolled heat pumps).
If there is no voltage to the circulation
pump, check if there is voltage from the I/O
card, see wiring diagram. If there is voltage
from the I/O card, check the components
between the I/O card and the circulation
pump.
If a component is defective, replace it.
Open closed main tap.
If a cable has come loose, reconnect it.
If there is a cable break, replace the cable.
If the high pressure switch does not open,
replace it.
If the high pressure switch opens too soon
or is always open, replace it.
Always ensure that there is a sufficiently
large water volume for the heat pump to
work against, i.e. for the heat to give off its
heat to.
VIGFI102
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