A.O. Smith T-H2-DV User Manual

T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
25
CONFIDENTIAL
10-7. AFR rod
Unit Part # #106 Takagi Part # EKK0E Checkpoint I
Function
Checks flame conditions during combustion.
When AFR rod detects unexpected flame conditions, the computer of the
water heater makes adjustments in the fan motor speed to compensate.
Failure events
1. Unable to detect flames when flames actually do occur
2. Detecting a false flame when no flames actually occur
Effects on the water
heater if AFR rod fails
1. The water heater stops operating. The "111” and/or “121” error code(s)
will display.
2. The water heater will not initiate the ignition process. The "721” error
code will display.
3. The fan motor speed cannot be modulated properly under abnormal flame
conditions, which can result in excessive CO emission.
Error codes when the
AFR rod fails
101 391 991
Diagnostic
1. Visual inspection: connection / braking of wires, soot on it.
2. Check voltages: proper range of values are shown below.
Color/Number of wires
Yellow(8) - AFR rod
(Between AFR rod and the
computer board)
(During operation)
More than DC 1 μA
The AFR rod is assembled with the flame rod.
AFR Rod
Flame rod
Leads to computer board
Detecting elements (AFR and flame rods)
3/4" (17.5mm)
1/4" (7.5mm)
1/2" (12mm)
1-1/8" (29.3mm)
1-3/4" (44mm)

A.O. Smith T-H2-DV Specifications

General

Brand	A.O. Smith
Model	T-H2-DV
Category	Water Heater
Language	English