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C - Electrical Components / Operation
Compressor Start Circuit
When the compressor circuit is first energized, the
solid state relay has low resistance (3-12 ohms),
and both the run and start windings are energized
to start the compressor. The run capacitor is being
bypassed by the relay, and it has a minor function
during compressor starting (See Figure C4).
Figure C4
Compressor Run Circuit
When the self-heating solid state relay has reached
sufficient temperature, it will abruptly change from
low resistance (3-12 ohms) to very high resistance
(10-20K ohms) and, in effect, switches off the start
windings.
The relay no longer shunts the run capacitor.
The run capacitor is now in series with the start
windings. The only purpose of the run capacitor
is to improve compressor operating efficiency,
which it does by correcting the power factor of the
compressor motor (See Figure C5).
Figure C5
Compressor Operating
Characteristics
• When the compressor electrical circuit is
energized, the start winding current causes
the relay to heat and switch off the start
winding circuit.
NOTE
The relay will switch off the start winding circuit
even though the compressor has not started
(as when attempting to re-start after momentary
power interruption).
• The overload protector is designed and
calibrated to open the compressor electrical
circuit with locked rotor run winding current
on.
• With an open relay, the compressor will not
start since there is little or no current to the
start windings. The overload protector will
open due to high locked rotor run winding
current.
• With a shorted relay or capacitor, the
compressor will start, and the overload
protector will open.
• With an open or weak capacitor, the
compressor will start and run. The
compressor, however, will be operating at
reduced efficiency of energy usage.
• If the compressor casing gets too hot, it
will shut down on the overload. After the
compressor has cooled down, the overload
will reset and the compressor will restart.
• In rear mounted compressors, the overload
will cycle the compressor on and off if the
refrigerator is set in so tight that the air can't
circulate around the condenser. In air cooled
condensers, the overload will cut the unit off
if the condenser becomes blocked or the fan
motor stops running.
15
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