contact as a good connection is a must) and the other probe in turn to each compressor terminal
(see Figure 2.) If a reading is obtained, the compressor is grounded and must be replaced.
9.1.3 Checking the compressor efficiency
The reason for compressor inefficiency is normally due to broken or damaged suction and/or
discharge valves, reducing the ability of the compressor to pump refrigerant gas.
This condition can be checked as follows:
1. Install a piercing valve on the suction and discharge or liquid process tube.
2. Attach gauges to the high and low sides of the system.
3. Start the system and run a “cooling or heating performance test.”
If test shows:
A. Below normal high side pressure.
B. Above normal low side pressure.
C. Low temperature difference across coil.
The compressor valves are faulty - replace the compressor.
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 – 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.
9.1.6 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.
9.1.7 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
To Next Page
Loading...
Need help?
General
