Heat Controller RG-51G Service Manual page 9

Heat Controller, Inc.
C. Low temperature difference across coil.
The compressor valves are faulty - replace the compressor.
ThERMAL OVERLOAD (External)
Some compressors are equipped with an external overload which
is located in the compressor terminal box adjacent to the
compressor body (see Figure 3.) The overload is wired in series
with the common motor terminal. The overload senses both
amperage and compressor temperature. High motor temperature
or amperage heats the disc causing it to open and break the
circuit to the common motor terminal.
Heat generated within the compressor shell is usually due to:
1. High amperage.
2. Low refrigerant charge.
3. Frequent recycling.
4. Dirty condenser.
TERMINAL OVERLOAD – TEST (Compressor - External Type)
1. Remove overload.
2. Allow time for overload to reset before attempting to test.
3. Apply ohmmeter probes to terminals on overload wires. There should be continuity through the overload.
TERMINAL OVERLOAD (Internal)
Some model compressors are equipped with an internal overload. The overload is embedded in the motor windings
to sense the winding temperature and/or current draw. The overload is connected in series with the common motor
terminal.
Should the internal temperature and/or current draw become excessive, the contacts in the overload will open,
turning off the compressor. The overload will automatically reset, but may require several hours before the heat is
dissipated.
ChECKING ThE INTERNAL OVERLOAD (see Figure 4.)
1. With no power to unit, remove the leads from the compressor terminals.
2. Using an ohmmeter, test continuity between terminals C-S and C-R. If
continuous, the compressor overload is open and the compressor must
replaced.
FAN MOTOR
A single phase permanent split capacitor motor is used to drive the evaporator
blower and condenser fan. A self-resetting overload is located inside the motor to
protect against high temperature and high amperage conditions.
FAN MOTOR - TEST
Room Air Conditioner with R-410A
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RG-51G Service Manual
Figure 3: External overload
Figure 4: Internal overload
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