Whirlpool KRFC704FSS - Defrost and Moisture Control

For Service Technician Use Only
DIAGNOSTICS
1-18
n
French-Door Boom Mount Refrigerator
Defrost and Moisture Control

The defrost system is designed to remove ice build-up from the
Refrigerator Compartment (RC) and Freezer Compartment (FC)
evaporators when required. FC defrost is accomplished using
a heater, while RC defrost is accomplished using the relavely
warm air of the RC. The moisture control system uses heaters to
warm areas suscepble to condensaon.

The FC Evaporator is defrosted as necessary to remove frost
or ice buildup. Defrost is accomplished with a 115 VAC, 470 W
heater.
An Adapve Defrost Control (ADC) roune determines when a
defrost cycle is needed. ADC monitors Compressor operaon,
and the number of mes the FC door is opened are the primary
inputs to the ADC roune.

During defrost, 115 VAC power is applied to the heater from
GF2 board P2-7. The FC Evaporator Thermistor monitors the
temperature during defrost. When the FC Evaporator Thermistor
reads 50°F (10°C), defrost is ended by removing the 115 VAC
power from GF2 board P2-7.

There are two thermal fuses wired in series with the defrost
heater. The thermal fuses are designed to interrupt the defrost
cycle if the normal method does not funcon properly. The
thermal fuses open at 183°F (84°C), interrupng power to the
heater.

The RC Evaporator is defrosted at the end of each RC cooling
cycle. The RC Evaporator Fan runs for a period of me aer the
compleon of RC cooling. This defrosts the evaporator using the
relavely warmer air of the RC.
The fan runs unl the temperature dierenal between the RC
Evaporator Thermistor and the RC Air Thermistor is less than
1°F (-17°C). The fan will run for a maximum of 10 minutes, aer
which it shuts o, regardless of the temperature dierenal
between the thermistors.

The RC Evaporator is defrosted as necessary to remove frost
or ice buildup. Defrost is accomplished with a 115 VAC, 470 W
heater. An Adapve Defrost Control (ADC) roune determines
when a defrost cycle is needed. ADC monitors Compressor
operaon, and the number of mes the FC door is opened are
the primary inputs to the ADC roune.

During defrost, 115 VAC power is applied to the heater from
GF2 board P2-5. The FC Evaporator Thermistor monitors the
temperature during defrost. When the RC Evaporator Thermistor
reads 50°F (10°C), defrost is ended by removing the 115 VAC
power from GF2 board P2-5.

There is one thermal fuses wired in series with the defrost
heater. The thermal fuse are designed to interrupt the defrost
cycle if the normal method does not funcon properly. The
thermal fuses open at 183°F (84°C), interrupng power to the
heater.
Heater Voltage
Voltage
Source
Watts Resistance
Filter 115 VAC
GF2 board
P2-6
3 4800
IB Duct
(Cabinet)
115 VAC
GF2 board
P2-6
5.5 2375
Dispenser 12.7 VDC
Dispenser UI
J8-1
1.5 108
IB Duct
(Door)
12.7 VDC
Dispenser UI
J8-1
1.5 108
Mullion 14 VDC
Door UI
J2-3
11.5 17

The refrigerator has heaters in necessary locaons to prevent
condensaon. The heaters can be operated in one of two
acvaon modes. The default mode is for the heaters to cycle in
response to measured humidity. Humidity is measured by a
sensor located on the Main control.