Danfoss Fault Location Installation guide
REFRIGERATION AND AIR CONDITIONING
Technical information
Fault Location on
PL, TL, NL, FR Compressors
COMPRESSORS
This Hermetic Note is directed especially to the service network, for household appliances and similar. For detailed information on compressors see the
data sheets.
Compressors type PL, TL, NL, FR and partly SC are equipped with a PTC
starting device (fig. 1) or a relay and start capacitor (fig. 2). The motor protector
is built into the windings.
In the event of a start failure, with a cold compressor, up to 15 minutes can
elapse before the protector cuts out the compressor.
When the protector cuts out and the compressor is warm, it can take up to 1
hour before the protector cuts in the compressor again.
The compressor must not be started without the electrical equipment.
Before beginning systematic fault location, a good rule is to cut the supply
voltage for at least 5 minutes. This ensures that the PTC starting device has
cooled off and is ready for start.
A voltage drop or blackout within the first minutes of a pull down of the
appliance with cold compressor, can lead to an interlocking situation. A
compressor with PTC can not start at non equalized pressure and the PTC
does not cool down so fast. It can take more than 1 hour until the appliance
then operates normally again.
To avoid unneccessary protector operation and consequent waiting time, it is
important to carry out fault location in the sequence given below. Tests are
made according to desriptions on following page.
• Remove electrical equipment
• Check electrical connection between main and start pins of compressor
terminal
• Check electrical connection between main and common pins of
compressor terminal
• Replace compressor, if above connection checks failed
• Else, replace electrical equipment
If the compressor still does not operate, most probably it is no electrical
compressor failure. For more detailed fault location, see the tables.
General
Fault location
Electrical compressor
quick check
Fig. 1: PTC starting device Fig. 2: Starting relay
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