Frymaster Gas Rethermalizers FBKR18 Series - Manual (Page 36)

6-3
solenoid valve when the water level reaches the upper water level sensor and to de-energize the
solenoid when the water level drops below the upper water level sensor.
The board has four LEDs to assist in troubleshooting. Three of the LEDs (LATCH, WATER, and
HEAT) are located just to the right of the heat relay (K4). The fourth LED is not labeled. It is
located in the lower left portion of the board, just above a large orange resistor. When the latch,
water, and heat LEDs are illuminated, they indicate that the associated relay is closed. The
unlabeled LED indicates that 24VAC is being supplied to the interface board by the transformer.
TEMPERATURE PROBE
A temperature probe is located on the front centerline of the cookpot. The probe is a type of
thermostat in which the resistance varies directly with the temperature. That is, as the temperature
rises, so does resistance, at a rate of approximately 2 ohms for every 1
° of rise or fall. Circuitry in
the computer monitors the probe resistance and controls burner firing when the resistance exceeds or
falls below a programmed temperature (setpoint). The temperature is programmed by means of
number buttons on the face of the computer.
WATER LEVEL SENSORS
Two water level sensors are arranged one above the other on the left front of the cookpot. When
water contacts the sensors they are grounded. The lower sensor acts as a safety device to keep the
burner from firing when there is no water in the cookpot. When the sensor is grounded by contact
with water, a transistor on the interface board is biased and the blower relay (K5) pulls in, supplying
power to the blower and to the gas valve via the ignition modules. Grounding the upper water level
sensor causes another transistor on the interface board to bias and pull in the water relay (K6) which
closes the water solenoid valve, cutting off water flow into the cookpot.
6.2 Accessing the Rethermalizer for Servicing
DANGER
Water heated to cooking/rethermalizing temperature will cause severe burns. Never
attempt to move this appliance when filled with heated water or to transfer heated
water from one container to another.
DANGER
This equipment should be unplugged when servicing, except when electrical circuit
tests are required. Use extreme care when performing such tests.
This appliance may have more than one electrical power supply connection point.
Disconnect all power cords before servicing.
Inspection, testing, and repair of electrical components should be performed by an
authorized service agent only.
1. Shut off the gas supply to the unit. Unplug the electrical power cord. Disconnect the unit from
the gas supply.
2. Remove any attached restraining devices.