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240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
10-15. Hi-limit switch for exhaust
Part#
• 319143-104 (EKH6G)
Unit Part#
#472
Function
-Based on bi-metal thermal expansion.
-Detects excess temperature (more than 151˚F or 66˚C) of exhaust gas in
the exhaust chamber.
Failure events
1. Unable to detect excess temperature of gas if switch fails "closed".
2. Continuous detection of excess temperatures (regardless of what the
actual temperature is) if switch fails "open".
Effects on the water heater
if hi-limit switch for
exhaust fails
1. Unable to shut down the water heater if the exhaust gas temperature in
the exhaust chamber exceeds 151˚F (66˚C).
2. The water heater is always shut down immediately after the ignition
process, and the "941" error code will display.
Error codes when hi-limit
switch for exhaust fails
941 (Direct Vent Indoor models only)
Diagnostic
1. Visual inspection: connection/breakage of wires.
2. Check voltages and resistance: proper range of values shown below.
Color / Number of wires
White - White
Less than 1.0 Ω
Checkpoint
K2
When temperatures exceed 151 ˚F (66 ˚C), the reset button trips and switch goes to OFF mode.
ON mode : < 151 ˚F (66 ˚C) OFF mode: automatic restoration back to ON mode
3/4" ( 17 mm)
3/4" ( 18 mm)
1/4" (4.6 mm)
5/8" (14.5 mm)
1-3/8" (35 mm)
3/4" (18.4 mm)
3-7/8" (100 mm)
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