Compressors; Component Operation And Testing - Friedrich KQ08J50A-B Service & Parts Manual

COMPONENT OPERATION AND TESTING

WARNING
DISCONNECT ELECTRICAL POWER
TO THE UNIT BEFORE SERVICING OR
TESTING

COMPRESSORS

Compressors are single phase, 220 or 220/240
volt, depending on the model unit. All compressor
motors are permanent split capacitor type, using
only a running capacitor across the start and run
terminal.
All compressors are internally spring mounted
and externally mounted on rubber isolators.
COMPRESSOR WINDING TEST
(See Figure 1.)
Remove the compressor terminal box cover
and disconnect the wires from the terminals.
Using an ohmmeter, check continuity across
the following:
1. Terminal "C" and "S" - no continuity - open
winding - replace compressor.
2. Terminal "C" and "R" - no continuity - open
winding - replace compressor.
3. Terminal "R" and "S" - no continuity open
winding - replace compressor.
FIGURE 1 COMPRESSOR WINDING TEST
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GROUND TEST
Use an ohmmeter set on its highest scale. Touch
one lead to the compressor body (clean point
of 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.
FIGURE 2 TYPICAL GROUND TEST
CHECKING 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 gages 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 the coil.
The compressor valves are faulty - replace
the compressor.