T-M50 / T-M50 ASME Service manual
Ver. 1.05
32
CONFIDENTIAL
10-17. GFI
Unit Part #
#720
AOS Part #
EM207
Checkpoint
A,A1
Function
-Detects electrical leakage in the water heater.
-Stops providing power to the water heater in the case of electrical leakage.
Failure event
1. ON-failure: Always in the ON mode (never trips).
2. OFF-failure: Always in the OFF mode (always stays tripped).
Effects on the water
heater if the GFI fails
1. ON-failure: GFI cannot detect electrical leakage within the water heater.
2. OFF-failure: the water heater does not receive any power from the GFI,
which means the water heater cannot operate.
Error codes when the GFI
fails
N/A
Diagnostic
1. Visual inspection: connection / breakage of wires and/or some signs of
electrical damage on the GFI.
2. Check the power supply to the GFI. If the red LED on the GFI lights up
after pressing the “test“ button, the GFI is receiving power. After verifying the
power supply, verify that 100 VAC is entering and leaving the GFI.
Color/Number of wires
N/A
From transformer
To the computer board
1
-
7
/
8
"
(
5
0
m
m
)
3
/
4
"
(
2
0
m
m
)
2 - 3 / 4 " ( 7 0 m m )
1 - 7 / 8 " ( 5 0 m m )
