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Mullion Heaters
The refrigerator utilizes 2 AC mullion heaters and
1 DC mullion heater. They are the articulating door
mullion (DC), fresh food/freezer mullion (AC), and
double drawer mullion heaters (AC).
The 3 mullion heaters are controlled by the main
board software logic. The main control board takes
into account the percentage of room humidity,
room temperature, and either freezer or fresh food
temperatures. As the room humidity increases,
the amount of voltage supplied to the heaters
is increased to keep the mullion surfaces from
sweating. At lowest humidity, the articulating door
mullion and fresh food/freezer mullion may turn off
completely, but the double drawer mullion heater
will always have some voltage present.
If the control panel is not equipped with an energy
saver pad, the heaters are controlled automatically
by the board based on thermistor and humidity
sensor input.
If the energy saver selection (if available) is off, all
heaters are on.
When the energy saver selection (if available) is on,
the articulating door mullion and the fresh food/
freezer mullion are off. The double drawer mullion
heater is on at a lower rate.
The double drawer mullion heater will not operate
with either freezer drawer in the open position.
Every 20 minutes, the main control board utilizes a
duty cycle to monitor and react to the condition of
the humidity sensor. Control board corrections, if
needed, are made at a speci
fi
c time period during
the duty cycle.
If the control detects a failed humidity sensor, and
the energy saver (if available) is off, all mullion
heaters will be operated at 100%.
If the control detects a failed humidity sensor, and
the energy saver (if available) is on, the double
drawer mullion heater will be operated and cycle
at a rate of 21% on time and 79% off time. The
articulating door and fresh food/freezer mullion
heaters will remain off.
The double door and horizontal mullion heaters
are off during ice dispense to reduce power supply
output. They remain off for 5 more seconds after ice
dispense completed.
Sweat or frost on mullion surfaces indicate
malfunctioning heaters, wiring, or control board.
The double door and horizontal mullion heaters
can only operate when the over-temperature
thermostat contacts are closed.
Applied voltage to the double door and horizontal
mullion heaters can be tested at main control board
J7-9 to J12.
The horizontal mullion heater is not replaceable. The
double drawer mullion heater can be replaced as a
separate part. (See
Double Drawer Mullion Assembly
.)
CLEAR
WHITE
ORANGE
ORANGE
NEUTRAL OUTPUT
ORANGE
ORANGE
ORANGE
PINK
OVER TEMPERATURE
THERMOSTAT
DD MULLION
HEATER
J7-9
J12
MAIN CONTR
OL BO
ARD
R=827
CLEAR
YELLOW/WHITE
PINK
R=1653
HORIZONTAL MULLION
HTR BETWEEN FF & FZ
ORANGE
YELLOW/WHITE
(
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)
