Thermal Fuse; Low Ambient Heater - Fisher & Paykel RF201A Service Manual

819091D
defrost history, the number of door openings, and the compressor run time are used to determine the interval
between defrosting. The typical time interval for defrosts is between 12 hours and 1 day. However it can be
as short as 3 hours or as long as 70.8 hours depending on the usage and environment.

Thermal Fuse

There are two thermal fuses mounted in the wiring harness of the defrost element, having a tripping
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temperature of 160 F. Once open circuit they cannot be reset. Replacement is part of the element heater
assembly.
These fuses in both leads of the element protect the refrigerator from any over heating through failure of the
element itself or a triac failure in the power / control module. Both sides are protected in case phase and
neutral are reversed.
NOTE: Care should be taken if manually defrosting the evaporator if using heat guns that the thermal fuses
are not over heated.

Low Ambient Heater

In low ambient temperatures, a 12 Volt, 7 Watt low power heater is used to keep the temperature in the
Provision compartment above freezing. The ambient heater is controlled by the power / control module which
uses pulse width modulation (PWM) to run the heater at 58% to give 4.1 watts of heat. The ambient heater is
situated in the divider partition. The element has the purpose of warming the area if the ambient becomes too
low, hence in the "B" models, the element is on when the cabinet cycles off as the crispers could freeze. The
heater will always be switched off during defrosting. There may be less than 4 cycles in the calculation if a
defrost has occurred or there were long cycle times.
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