Basic Test Procedures; Defective Compressor - Heat Controller BHD-301-G Service Manual

BHD-G Service Manual

5.Basic Test Procedures

5.1 DEFECTIVE COMPRESSOR

Compressors are single phase, 115 volt. 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
Remove compressor terminal box cover and disconnect wires from 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.
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.
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 line.
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.
THERMAL 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 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 cycling.
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.
Portable Dehumidifier with R-410A
7
Heat Controller, Inc.
Figure 1: Compressor winding test
Figure 2: Typical ground test