A SERVICE OF

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Page 4-3
The interaction between the thermostat and the safety valve is very important and critical to the
operation of the oven. The thermostat provides two separate functions each time it is turned on,
but first, we need to know what the thermostat does when it is in the “OFF” position. Even with the
thermostat in the “Off” position, a supply of gas from the manifold pipe is always available through
the thermostat to the oven pilot assembly. It supplies enough gas to maintain a constant or
“standing” pilot flame in the oven at all times (see Figure 4-4).
Standing
Pilot Flame
Standing Pilot
Assembly
When the thermostat is turned “ON” to any temperature, its primary function is to increase the flow
of gas to the oven pilot assembly so that the “standing” pilot flame enlarges to create a “larger
standing pilot” or a “
heater pilot flame
.” This larger flame is deflected by a
flame spreader
(see
Figure 4-5) to heat the sensing bulb from the safety valve and hydraulically open it.
Figure 4-4
Flame Spreader
Safety Valve
Sensing Bulb
Heater Pilot
Flame Wraps
Around Sensor
Flame Spreads
Down To Sensing Bulb
Heater Pilot
Figure 4-5
OFF
N
A
T
L
P
BROIL
200
250
300
350
400
450
500
550
OFF
OFF
N
A
T
L
P
BROIL
200
250
300
350
400
450
500
550
OFF
The Standing Pilot
Thermostat Off
The Standing Pilot
Thermostat On