Danfoss DHP-A, Service Instructions Manual

Page: 43 / 86

Cause Troubleshooting Remedy
13. Blocked condenser on the water
side.
If there is no strainer in the heating sys-
tem, there is a risk of dirt sticking in the
condenser and blocking it. Unfortunately
there is no easy way of checking if the
condenser is blocked.
You can carry out a test by allowing the
compressor and circulation pumps to
remain in operation and after a while,
check that the pressure pipe becomes hot
and that the circulation pumps work (for
circ.pumps with a bleed screw, unscrew it
and feel if the pump rotor rotates using a
screwdriver).
Then read the temperature on both con-
nection pipes to the condenser:
If the temperature difference is <3°C, the
condenser is probably blocked.
If the temperature difference is 3-13°C, it is
probably not blocked.
If the temperature difference is >13°C, the
condenser is probably blocked.
If the condenser is thought to be
blocked, try flushing it. If this does not
work, it must be replaced
14. Blocked condenser on the refriger-
ant side.
Using manometer apparatus and ther-
mometer, check that the unit’s overheat-
ing is correct for the specific refrigerant.
If the condenser 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
Table 15. Problem – Alarm MS (motor protection)
Cause Troubleshooting Remedy
1. Phase drop or blown fuse. Check that all phases are present on the
terminal block for incoming supply. If not,
check the fuses in the cabinet.
Also check that all wiring is secure, if screw
terminals are used they must be properly
tightened, if phoenix flat spring terminals
are used, the cables must be secure in the
correct hole with load on the cable.
If any of the phases are missing, check
backwards towards the building’s main
electrical cabinet. If there are no phases
there, contact the network supplier.
2. Defective soft-starter (three-phase
heat pump).
Measurement check and establish that
when the I/O card gives a signal (there
must be voltage between A1 & A2 on the
soft-starter), the soft-starter releases all
three phases down to the compressor.
If the soft-starter does not release the
phases when it receives signals from the
I/O card, replace it.
3. Defective soft-starter ( single phase
heat pump).
Check measure and establish that when
the I/O card gives a signal (there must be
voltage between ON and N on the soft-
starter), the soft-starter releases the pha-
ses to the compressor.
If the soft-starter does not release the
phases when it receives signals from the
I/O card and does not alarm as below,
replace it.
4. Defective or incorrectly set motor
protection.
Use a hook-on meter to establish when
the motor protection deploys, check what
the motor protection is set to.
Compare with the table. For three phase
heat pumps all three phases must be sup-
plied.
If the motor protection is defective,
replace it.
If incorrectly set, adjust to the correct
value.
5. Cable break. Check the supply to the motor protection,
soft-starter or compressor.
If a cable is damaged, replace it.
Service instructions VMGFC302 – 41