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1
Thermostat calls for heat.
The control board sends 24 volts from damper terminal #2 on the control plug
to the flue damper.
2
Flue damper begins to rotate open. Once the flue damper is fully open, the damper end switch closes and 24 volts
is allowed to continue through damper to damper pin terminal #5.
3
4
Once pilot flame is proven, sparking will stop.
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Sequence of Operation
T
rial for ignition (three 90 second ignition trials, with 65 second pauses
between trials).
Control Board simultaneously sends:
1. 24 volts from control pin terminal #8, to “MV/PV”
terminal of gas valve (common terminal).
2. 24 volts from control pin terminal #2, to “PV”
terminal of gas valve to establish
gas flow at pilot.
3. Low current high voltage from “spark”
terminal, to generate spark at the pilot and
ignite pilot gas flow.
4. Pilot flame proving signal (measured in
micro-amps). from the “sense” terminal, to
prove pilot flame.
5
Once sparking stops, 24 volts is sent from control pin
terminal #5 on control board, to “MV” terminal on gas valve
to establish main burner gas flow. Main burners ignite from
the pilot flame.
The control board constantly monitors pilot flame through
the flame sensor rod. If pilot flame is lost, pilot and main
burners are shut down. After a 65 second inter-purge
period, the control will attempt to re-light the pilot beginning
at sequence 3 above.
7
Main burner fires until the thermostat is satisfied. The control
board interrupts 24 volts through the damper and the gas valve
circuit. Pilot and main burners are turned off.
8
Flue damper rotates to the closed position.
WIRING DIAGRAM
LOCKOUT CONDITION
Control board will go into “Soft Lockout” if the pilot cannot be lit
after 3 ignition trials. The water heater display indicates a lockout
condition by showing an error code number (62 or 63) with
“Service Needed” in the display window. Refer to error codes in
the diagnostic section of this Service Manual. In a “Soft Lockout”
condition, the control will wait for 60 minutes and then make 3
more attempts to light the pilot and establish the main burners.
Soft lockout reset is accomplished by depressing the lower right
button under “Reset” for 3 seconds.
If the water heater should reach 200 degrees F, then the high limit
control will shut off the burners and the water heater will go into a
“Hard Lockout”. Error code 65 will be shown in the water heater
display. The control can only be reset in the “service mode”,
which is detailed in the next section of this Service Manual.
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