A.O. Smith 120 trough 500 - Manual (Page 39)

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
38
STEP 16 FLAME RECTIFICATION
STEP 16. FLAME RECTIFICATION
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.
Sparking at the pilot will stop almost immediately after the ignition module senses the pilot flame.
IF THEN
Sparking continues after pilot is
established: • Check wire connections
• Check flame contact between hood
and lighter
• Clean pilot burner surfaces
• Replace pilot assembly
Sparking stops: • Go to step 17.