58300000194725 ARA EN B MAY 2016 Service Manual for Bosch 800 Series Gas Slide-in Ranges
Page 12 of 36
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Figure 4 NG/LP flame characteristics
5.2 Flame Characteristics:
Yellow Flames: Further adjustment is
needed
Yellow Tips on Outer Cones:
Normal for LP gas
Soft Blue Flames: Normal for natural
gas
5.3 Spark Module
The 5-point, 120V 60Hz 2VA flame-sensing spark module has
terminal connections on the top for power and the spark switch wires
and on the bottom for the spark igniter (electrode) wires.
5.3.1 Flame Rectification
Gas cooktop spark modules use flame rectification to reliably re-ignite
a burner if the flame goes out.
Flame rectification occurs when flame molecules ionize, allowing them
to conduct electricity. Because the cooktop frame is much larger than
the spark igniters (electrodes), the flame acts as an AC to DC rectifier.
The spark module applies an AC voltage to the spark igniter, which is
rectified from AC to DC. The spark module measures this small micro
amp (µA) DC current and senses a flame is present. If the current is
interrupted, the spark module senses the flame has gone out and re-
ignites the burner.
If burner bases aren’t solidly grounded, they won’t be connected to
the cooktop frame, the circuit through the cooktop frame to the spark
module won’t be connected, and there will be no flame rectification
(no DC voltage sensed), so burners won’t stay lit.
Igniter (electrode) wire connections
Spark switch and power connections
Figure 5 Five-point spark module
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