Step 8: Flame Rectification - A.O. Smith BTR 120-400 Service Handbook

STEP 8: FLAME RECTIFICATION

CONDITION:
• Pilot Flame Noted, Pilot Sparking Continues, No Main Burner.
Note: Flame rectification means that an alternating current (AC) signal is changed to a direct current (DC)
signal. The pilot flame is the 'switch' which connects the pilot hood to the igniter and ground. If the
pilot hood and igniter sensor had the same surface area, the flame 'switch' would conduct an AC
signal. Because the pilot surface is greater than the igniter surface, the signal becomes a DC current
that the module can interpret. The pilot hood must be properly grounded and the pilot flame must
remain in contact with both surfaces for the flame proving signal to remain constant. If the signal is
broken for just 8 tenths of a second, the heater will cycle off. Sparking at the pilot will continue if
an insufficient signal is received by the module. The pilot burner mounts on the left side of
the main burner.
Sparking at the pilot will stop almost immediately after the ignition module senses the pilot flame.
IF
Sparking continues after pilot is established:
Sparking stops:
24 Servicing should only be performed by a Qualified Service Technician
THEN
• Check wire connections.
• Check flame contact between hood and lighter.
• Clean pilot burner surfaces.
• Replace pilot assembly.
• Go to Step 9.