9.1.4 Terminal overload (external)
Some compressors are equipped with an external overload which is located in the compressor terminal box
adjacent to the compressor body. The overload is wired in series with the common motor terminal. The
overload senses both major 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.
9.1.5 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 it may
require several
hours before the heat
is dissipated.
9.1.6 Checking the internal overload
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 not continuous, the compressor
overload is open and the compressor must be replaced.
9.2 Sealed refrigeration system repairs
9.2.1 Equipment require
1. Voltmeter
2. Ammeter
3. Ohmmeter
4. Refrigerant Recovery System
5. Vacuum Pump (capable of 200 microns or less vacuum)
6. Acetylene Welder
7. Electronic Halogen Leak Detector (G.E. Type H-6 or equivalent.)
8. Accurate refrigerant charge measuring device such as:
a. Balance Scales - 1/2 oz. accuracy (=0.0141747615625 kg)
b. Charging Board - 1/2 oz. accuracy (=0.0141747615625 kg)
9. High Pressure Gauge - (0 - 400 lbs.) (= 0 – 181 kg)
10. Low Pressure Gauge - (30 - 150 lbs.) (=14 – 68 kg)
11. Vacuum Gauge - (0 - 1000 microns)
9.2.2 Equipment must be capable of:
1. Recovery CFCs as low as 5%.
2. Evacuation from both the high side and low side of the system simultaneously.
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