Carrier Residential Air Conditioners and Heat Pumps Application Manualline page 21

9. If a compressor hums but won't start it could indicate either
a voltage or amperage issue. Verify adequate voltage and
operational start components if installed. If it is drawing
excessive amperage and voltage doesn't appear to be the
problem it may be assumed a locked condition. Ensure
refrigerant has had ample time to equalize and boil out of
the compressor before condemning.
10. When a heat pump switches into and out of defrost, a
"swooshing" noise is expected due to the rapid pressure
change within the system. However customers sometimes
complain that the noise is excessive, or it is sometimes
accompanied by a "groaning, or howling" noise. When
receiving these complaints, Quiet Shift- -2 (if available) may
improve the noise, but will probably not eliminate it totally.
Check that the defrost thermostat or thermistor is operating
properly. Insulating the defrost sensing device may also
help. If the howling or groaning noise is intermittent,
replacing the reversing valve may or may not help.
11. Rattling that occurs during a shift into or out of defrost on a
heat pump could indicate a pressure differential issue. This
is usually a brief occurrence (under 60 seconds) and can be
remedied by incorporating Quiet Shift- -2, if available. This
is a device that shuts down the compressor during the
defrost shift for approximately 1 minute allowing the
pressures to equalize. It is enabled by either a dip switch
setting on the defrost board, or in the User Interface on
communicating systems. Verify proper system charge as
well.
?
?
POWER OFF!
?
OHMMETER
0-10Ω SCALE
1
2
5.2Ω
0.6Ω
2
3
(EXAMPLE)
TO DETERMINE INTERNAL CONNECTIONS OF SINGLE-
PHASE MOTORS (C,S,R) EXCEPT SHADED-POLE
DEDUCTION:
1 3
2 3
1
1 2 (REMAINING RESISTANCE)
5.8Ω
3
Fig. 14 – Identifying Compressor Terminals
Fig. 12 – Split Post Grommet part number: KA75UG100
Note: Long radius elbows recommended
Fig. 13 – Suction Line Loop
(GREATEST RESISTANCE)
5.8Ω (OHM)
(SMALLEST RESISTANCE)
0.6Ω
5.2Ω
21
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)
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