Surge Box - A.O. Smith T-M50 ASME Service Manual

10-20. Surge box

Unit Part #
Function
Failure event
Effects on the water
heater if the Surge box
fails
Error codes when the
Surge box fails
Diagnostic
Color/Number of wires
Fuse: 10 A
Surge absorber A: 220 V
#722 AOS Part #
Protects the unit from high voltage and/or high electric current caused by
lightning.
There are 2 types of surge absorbers in the Water heater. Surge absorber A
is activated by voltage higher than 220 V, the other one is activated by
voltage higher than 680 V.
1. Open-failure of the absorber and/or fuse.
2. Short-failure of the absorber.
1. Unable to protect the computer board if high voltage gets applied to the
unit. The computer board can short out, stopping all operations.
2. The unit cannot operate because the absorber shorted out, causing the
fuse to break open.
1. V isual inspection:
connection/breakage of wires.
2. Check resistance and voltage: proper range of values shown below.
White-Black 108 to 132 VAC
1- 3 / 4" ( 4 3 . 2 mm )
1 /2 " ( 1 3 . 6 mm )
T-M50 / T-M50 ASME Service manual
EM385
N/A
burn marks
Surge absorber B: 680 V
35
CONFIDENTIAL
Ver. 1.05
Checkpoint A2,A3
on components
3 1 /3 2 " ( 2 5m m )
and/or