Whirlpool Polara GR556LRK Service Manual page 22

REFRIGERATION
COOLING MODULE
The refrigeration cooling module is a conven-
tional capillary tube system that is charged with
R134a refrigerant. A double-shafted fan motor
provides air flow for the evaporator and con-
denser. The fan motor runs constantly during
refrigeration operation.
The refrigeration module uses two normally-
closed bimetals that are wired in series, and
are mounted one over the other (see the photo).
The top bimetal cycles the compressor off,
while the fan continues to operate and provide
defrost. When the bimetal opens, the compres-
sor cycles off, and the continuous air flow
warms the evaporator to remove all frost accu-
mulation.
The top bimetal opens at 22°F (±3°) to stop the
compressor, and closes at 39°F (±3°) after the
evaporator has defrosted.
The lower bimetal is used as a backup to
prevent an incomplete defrost condition from
occurring. It will only open if ice accumulates at
the center of the evaporator, causing reduced
air flow, and lower temperature at the middle of
the evaporator.
The lower bimetal opens at 18°F (±3°) to stop
the compressor, and closes at 36°F (±3°) after
the evaporator has defrosted.
A recessed sump channel is formed in the base
of the module, and provides an area for the
condensate water to collect and evaporate.
Warm air from the condenser speeds the evapo-
ration of this water. During refrigeration, it is
normal to feel this warm air circulating around
the base and rear of the range.
3-2
Primary (Top)
Bimetal
Defrost Backup
(Lower) Bimetal