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valve via a normally closed high-limit switch (and, in fryers with built-in filtration systems, a
normally closed drain safety switch). Simultaneously, the module causes the ignitor to spark for 4
seconds to light the burner. A flame sensor verifies the burner ignition by measuring the flow of
microamps through the flame. If the burner does not light (or is extinguished), current to the
ignition module is cut, the gas valve closes, and the ignition module “locks out” until the power
switch is turned off and then back on. A probe monitors the temperature in the frypot. When the
programmed setpoint temperature is reached, resistance in the probe causes the heat cycle circuitry
in the controller to cut off current flow through the heat relay. This in turn cuts off the 24 VAC to
the ignition module, causing the gas valve to close.
1.1.2 Interface Board
The information contained in this section applies to Pro (H50/55) Series gas fryers ONLY.
All fryers in this series have an interface board located in the component box behind the control
panel. The interface board provides a link between the controller/computer and the fryer’s
individual components without requiring excessive wiring, and allows the controller to execute
commands from one central point. This standard interface board is also used in a number of fryer
types besides the Pro Series.
K2 and K3 are double-pole-double-throw (dpdt) relays that supply 24VAC to the ignition and gas
valve circuits, as well as 120VAC to the blower motor. The relays on this board plug into sockets,
and if either fails, it can be replaced individually.
LEDs (labeled D1 through D7) are arrayed around the board to assist in troubleshooting.
K4
K1
SOUND
1
2
3
GND
GND
V2D
PWR
AD
AS
V2S
GND
GV
PWR
12V
AIR
24V
PWR
GND
V1D
PWR
ALR
V1S
GV
GND
J2
INTERFACE BOARD P/N 106-0386
GND
J3
3 6 9 12
2 5 8 11
1 4 7 10
J1
3 6 9 12
2 5 8 11
1 4 7 10
15
12963
14
11852
13
10741
K2 K3
HEAT
RELAY
AND
BLOWER
MOTOR
RELAY
D1
D2
D3
D4
D6
D7
Blower
Motor
2 Amp
D5
HEAT
RELAY
AND
BLOWER
MOTOR
RELAY
F2 Ignition
2 AMP Module
D1
24 VAC to left gas valve (dual vat only)
D2
24 VAC to left ignition module
D3
24 VAC from transformer
D4
24 VAC to right ignition module
D5
24 VAC to gas valve (right valve if dual vat)
D6
12 VAC from transformer
D7
CE and Japanese units only: air switch closed
INTERFACE BOARD
LED DIAGNOSTIC LIGHTS
NOTE: Although the printing on some boards may indicate 2 Amp fuses, 3 Amp fuses (P/N
807-3843) must be used. In full-vat fryers, the relay for the left side (K2) may not be present.
The chart on the following page illustrates current flow through the board, and the table at the top of
page 1-4 identifies frequently used test points.