HEAT CYCLE DEFINITIONS

STATE

DESCRIPTION

Pre-purge

If the heat engine initial call-for-heat is successful (all checks are passed), the combustion fan

 

is energized. The fan is started at a high speed for several seconds and the system verifies the

 

fan speed. Input signals (from other parts of the water heater) are verified before completion of

 

pre-purge including fan current verification. If one of the checks fails then the unit moves into

 

the post-purge mode followed by the hard lockout mode and the appropriate error is displayed

 

(see Error Code List and Clear-out Procedure).

Inter-Purge

If the flame presence is detected the control delays a pre-determined amount of time keeping

 

the spark igniter energized. If flame presence is not detected within 5 seconds from the

 

moment the gas was allowed in the combustion chamber (three ignition trials) then the control

 

will initiate an ignition re-try for two more times. If flame presence cannot be verified within

 

the given timing and after the ignitions’ re-try (if applicable), the system enters the post-purge

 

mode and the gas flow is turned off.

Post-Purge

The heat engine gas valve is now turned off and the fan speed is changed to high speed for

 

a predetermined time followed by a change of fan speed to a low value for the remaining

 

duration of the post purge mode. The control will also verify that the proper conditions are

 

maintained and there is no flame current sensed from the flame rod. If during the first stage

 

of the post-purge mode (high speed fan operation) conditions for a new call for heat are met

 

then the system will allow the state change to “Initial call for heat” only after the first stage of

 

the post-purge mode is complete.

Standby Mode

After successful completion of post-purge, the fan is turned off and the control will wait until

 

the determined conditions for a call for heat are met. In standby mode the unit continually

 

monitors the input and output conditions and if abnormal conditions are detected the unit will

 

enter in a lockout mode. If a call for heat is required and all checks are passed, the control

 

will return to the initial call for heat state.

Lockout mode

This is a non-operational mode following the detection of an error in the system. In this stage

 

the system displays an error message and continuously monitors input and output parameters.

 

The system can move from this state into the stand-by mode only if the error is cleared (typical

 

values for input and output parameters are recorded).

Proven Ignition

Once the power is turned on, the self-inspection is getting a normal status, water is turned

 

on and fan’s current is normal then the ignition process will start for 5 seconds. If ignition is

 

successful, the heater will go to normal combustion state and the ignition sparking will stop

 

after 3 seconds. If ignition fails, the control will attempt to cycle through the heating stage

 

three times and then attempt to re-ignite the gas. If ignition cannot be achieved, the control

 

will end ignition attempts and prevent any more heating cycles, close the gas valve, turn the

 

blower on, and display the E28 error message to the user.

 

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American Water Heater 1010 319869-000 warranty Heat Cycle Definitions State Description