White Rodgers Integrated Temperature Control-High Limit Switch - A.O. Smith BTR 120-400 Service Handbook

WHITE RODGERS INTEGRATED TEMPERATURE CONTROL-HIGH LIMIT
SWITCH
The digital thermostat contains the high limit (energy cutout) switch. The high limit switch interrupts main
burner gas flow should the water temperature reach 203°F (95°C).
In the event of high limit switch operation, the water heater cannot be restarted unless the water temperature
is reduced to approximately 120°F (49°C). The high limit reset button on the front of the control then needs
to be depressed.
Continued manual resetting of high limit control, preceded by higher than usual water temperature is evidence
of high limit switch operation. The following is a possible reason for high limit switch operation:
• A malfunction in the thermostatic controls would allow the gas control valve to remain open causing
water temperature to exceed the thermostat setting. The water temperature would continue to rise until
high limit switch operation.
Contact your dealer or service agent if continued high limit switch operation occurs.
4 Status LEDs
E3
To Upper
Temperature Probe
E1
To HSI Control
12 Pin Plug
E3
To Lower
Temperature Probe
STATUS LEDS
The Power Status LED is green, ECO, ECO Reset, and Call for Heat Status LEDs are red.
LED STATUS
Power On.
Call for heat On.
Power On.
ECO On.
Power On.
Reset On.
Servicing should only be performed by a Qualified Service Technician
3 Amp Automotive Fuse
INDICATION
Power is On, a call for heat
currently active.
ECO has locked out control, tank
temperature exceeded 203°F.
Tank temperature has cooled
below 120°F after ECO lock out,
can be reset.
Temperature
Adjustment Dial
Manual Reset
for ECO
E2
120 VAC from
Control Board
ACTION TO TAKE
Normal operation.
Check for excessive
temperature/ cool down
tank.
Press manual reset,
determine cause for ECO
lock out.
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