Danfoss DHP-A Service Instructions Manual page 50

Table 27. Problem – Shrieking, whistling noise
Cause
1. Whistling expansion valve.
2. Noise from the soft-starter.
3. The compressor's IPR valve opens.
Table 28. Problem – Noise – miscellaneous
Cause
1. Vibrating protective sleeves on the
pressure switches.
2. Vibration noise from the electrical
installation.
3. The heat pump is not level.
4. General noise problems
48 – Service instructions VMGFC302
Troubleshooting
1. Take overheating readings, adjust
to the recommended value.
2. Open and close the valve fully in
and out.
3. Adjust the expansion valve to rec-
ommended overheating value
again.
Measurement check the input and output
phases for the soft-starter as well as the
control signals from the I/O card (see wir-
ing diagram).
The compressor has an integrated IPR
valve that opens at 28 ±3 bar.
When the valve opens, pressure equalizes
between the compressor's high and low
pressure sides and a milling/whistling
sound is heard.
To establish whether the valve opens at
the correct pressure, connect a manome-
ter on the high and low pressure sides.
When the valve opens, this is indicated by
the pressure on the low pressure side ris-
ing and reaching the pressure on the high
pressure side.
Check at what pressure the valve starts to
open.
Troubleshooting
Establish where the vibration noise is com-
ing from.
Check for electrical steps or similar devices
screwed to the heat pump and wall. These
can cause vibrations and noise.
Check that the heat pump is level by using
a spirit level.
Check that the heat pump is supported by
all four feet.
Carry out preventative measures. See
Installation instructions.
Remedy
Check if the noise has stopped. If not,
continue with point 2.
Continue with point 3.
If the problem persists, replace the
expansion valve.
If the soft-starter is defective, replace it.
If it opens at too low a pressure, replace
the compressor.
Remedy
Prevent the protection sleeve vibrating
by using insulation tape for example.
Carry out according to the installation
instructions.
If the heat pump is not level, adjust using
the feet.
Example:
•
Improve the acoustic environment
in the area where the heat pump in
located by installing acoustic panels
on the walls and ceiling.
•
Install a hood on the compressor
(most effective for high frequencies).