Electrical Failures - Bryant Base Series Application Manual And Service Manual

Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
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POWER OFF!
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OHMMETER
0-10 SCALE
1
2
5.2
0.6
2
3

Electrical Failures

The compressor mechanical pump is driven by an electric motor within
its hermetic shell. In electrical failures, compressor does not run
although external electrical and mechanical systems appear normal.
Compressor must be checked electrically for abnormalities.
Before troubleshooting compressor motor, review this description of
compressor motor terminal identification.
Single-Phase Motors
To identify terminals C, S, and R:
1. Turn off all unit power.
2. Discharge run and start capacitors to prevent shock.
3. Remove all wires from motor terminals.
4. Read resistance between all pairs of terminals using an ohmmeter
on 0-10 ohm scale.
5. Determine 2 terminals that provide greatest resistance reading.
Through elimination, remaining terminal must be common (C). Greatest
resistance between common (C) and another terminal indicates the start
winding because it has more turns. This terminal is the start (S). The
remaining terminal will be run winding (R).
NOTE: If compressor is hot, allow time to cool and internal line break
to reset. There is an internal line break protector which must be closed.
All compressors are equipped with internal motor protection. If motor
becomes hot for any reason, protector opens. Compressor should always
be allowed to cool and protector to close before troubleshooting. Always
turn off all power to unit and disconnect leads at compressor terminals
before taking readings.
Most common motor failures are due to either an open, grounded, or
short circuit. When a compressor fails to start or run, 3 tests can help
determine the problem. First, all possible external causes should be
eliminated, such as overloads, improper voltage, pressure equalization,
defective capacitor(s), relays, wiring, etc. Compressor has internal line
break overload, so be certain it is closed.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
(EXAMPLE)
TO DETERMINE INTERNAL CONNECTIONS OF SINGLE-
PHASE MOTORS (C,S,R) EXCEPT SHADED-POLE
DEDUCTION:
1 3
2 3
1
1 2
5.8
3
Fig. 18 – Identifying Compressor Terminals
(GREATEST RESISTANCE)
5.8 (OHM)
(SMALLEST RESISTANCE)
0.6
(REMAINING RESISTANCE)
5.2
Open Circuit
UNIT PERSONAL INJURY HAZARD
Failure to follow this warning could result in personal injury.
Use caution when working near compressor terminals.
terminals have the potential to cause personal injury.
Never put face or body directly in line with terminals.
To determine if any winding has a break in the internal wires and current
is unable to pass through, follow these steps:
1. Be sure all power is off.
2. Discharge all capacitors.
3. Remove wires from terminals C, S, and R.
4. Check resistance from C-R, C-S, and R-S using an ohmmeter on
0-1000 ohm scale.
Because winding resistances are usually less than 10 ohms, each reading
appears to be approximately 0 ohm. If resistance remains at 1000 ohms,
an open or break exists and compressor should be replaced.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Be sure internal line break overload is not temporarily open.
24
RUN WINDING (R)
START WINDING (S)
2
IS COMMON (C)
BY ELIMINATION
2
IS COMMON,
THEREFORE, 1 IS
START WINDING (S)
3 IS RUN WINDING (R)
WARNING
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CAUTION
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A88344
Damaged