Cause
Troubleshooting
Remedy
4. Drying filter blockage.
Check the temperature difference above the drying filter.
A difference of max 1°C is permissible. If the difference is
greater, the filter is blocked. Take a reading during opera-
tion.
If the drying filter is sealed, replace it.
5. Blocked evaporator on
the refrigerant side.
Using manometer apparatus and thermometer, check that
the unit’s overheating is correct for the specific refrigerant.
If the evaporator is thought to be blocked
by oil for example, try blowing nitrogen
through it to release the oil. If this does not
work, it must be replaced
Problem – Alarm HP (high pressure switch)
Cause
Troubleshooting
Remedy
1. Air in the heating system. Listen for air in the heat pump and heating system.
Bleed the heating system according to the
installation instructions.
2. Blocked strainer in the
heating system.
Check that the strainer is not blocked.
Clean the strainer if necessary.
3. Closed or partially closed
thermostats/valves in the
heating system.
Check that the thermostats/valves in the heating system
are open.
Open closed thermostats/valves.
4. The circulation pump that
is defective or has jammed.
Is there voltage and 0 – 10V signal (applies to A classed cir-
culation pumps) up to the circulation pump?
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 heat pumps
in not valid ).
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.
5. Shut-off main tap in heat-
ing system.
Check that the main tap is open.
Open closed main tap.
6. Cable break or loose cable
to high pressure switch.
▪
Check that both cables are connected to the pressure
switch.
▪
Using the buzzer, check that there are no cable
breaks. In order to do this, disconnect the cables from
the pressure switch and circuit board.
If a cable has come loose, reconnect it.
If there is a cable break, replace the cable.
7. The high pressure switch
does not open.
▪
Incorrect pressure switch installed. Same or higher
break pressure than the high pressure switch. See
marking.
▪
Pressure switch fault, opens at a higher pressure than
indicated (mark pressure). Check using the manome-
ter apparatus.
▪
Defective pressure switch, never opens.
If the high pressure switch does not open,
replace it.
Service Instructions
DHP-AQ
VMGFJ202
Danfoss Heating Solutions
16
