A.O. Smith 403, 400, 402 Status Displayed True Condition Input, Menu Screen, Temperature Screen

The following status information is displayed from the System Status Screen:

Status Displayed	*(True Condition)	Input	Output
ECO	Outlet temperature too high	open	- - - -
LW/CO	Water Level low	open	- - - -
Blk Flue	Flue blocked	open	- - - -
Flow	Water flowing	closed	- - - -
Low Gas	Gas pressure low	open	- - - -
Tstat	Thermostat requesting heat	closed	- - - -
Hi Limit	Outlet temp exceeds High Limit setpoint	- - - -	- - - -
Pump	Pump output activated	- - - -	On
IRI Gas Pwr	IRI output relay activated	- - - -	On
IRI Gas	IRI Gas Valve on	closed	- - - -
Pwr Vent	Power Vent running	closed	- - - -
Alarm	Alarm output activated	- - - -	On
Pwr Vent Pwr	Power Vent output relay activated	- - - -	On
	- - - - STAGES 1 to 2 - - - -
BlwHi Prv	Blower pressure sufficient	closed	- - - -
Blw Hi	Blower High output activated	- - - -	On
BlwLo Prv	Blower pressure sufficient (not used at this time)	closed	- - - -
Blw Lo	Blower low output activated (not used at this time)	- - - -	On
Ignt Cur	Igniter current sufficient for ignition	- - - -	- - - -
Ignit	Igniter output is activated	- - - -	On
Gas Relay	Gas output relay activated	- - - -	On
Hi Gas	Gas pressure too high	open	- - - -
Flame	Flame detected	- - - -	- - - -

•Menu Screen:

Displayed when the user presses the "Menu" key. This screen is the selection point for the other 9 screens.

•Temperature Screen:

Displays the sensed temperatures of the Outlet, Inlet, and Tank probes. Also displayed is the calculated Delta T (Outlet minus Inlet) for the system. Shorted ("Short") and disconnected ("----") probes are also displayed.

•System Status Screen:

This screen is used to view the status of switch inputs and output states. An asterisk (*) is displayed next to the label when the status is "True" (the description is fulfilled). For example, if water is flowing, or detected by the flow sensor, then an "*" will appear in front of the Flow label (i.e. *Flow). Another example would be the ECO switch. If the outlet temperature is too high the display will show: *ECO.

NOTE: The LWCO, IRI Gas Valve, Powered Vent, High Gas, and Low Gas inputs are optional inputs. Flame sensing, Igniters, and Blowers are optional on Stages 2, 3 and 4. (Except on a 4-stage system, stage 2 always has an Igniter, Blower, and Flame Sensor. Those dipswitches on stage 2 are not relevant.) One or two speed blowers can be used on any stage.

The System monitors the inputs at these times:

•ECO, LWCO, Blocked Flue, Low Gas, Hi Limit, and Hi Gas - at all times for a fault condition.

•Tstat - at all times for open/closed conditions.

•IRI Gas and Powered Vent - for an on condition when their outputs (Pump, IRI Gas Pwr, Powered Vent Power) are turned on and an off condition at all other times.

•Flow - for an on condition when the pump is on (no check for off state)

•Blower Prover - when the Blower is on.

•Igniter Current - for an on condition approximately 18 seconds

after the Igniter is turned on until the igniter is turned off and an off condition at all other times.

•Flame - for an on condition approximately 5 seconds after the gas valve is turned on until the valve is turned off and at all other times for an off condition.

Control Status Screen:

Displays the status that the CCB and FCB micros are in. The CCB has 5 possible states and the FCB's have 9. The normal CCB states sequence is to move from Idle, to Pre-Circulate, then to Heating Stage 1-2-3-4 when a call for heat is initiated. Once heat has been satisfied or the Thermostat is opened, the sequence moves to Post- Circulate and then back to Idle. If a fault occurs at any time, the process jumps out of sequence and goes directly to the appropriate Hard or Soft Fault state.

Description of CCB control states:

•Idle:

The yellow "Standby" LED is turned on and the system waits for a heat request (determined by the Thermostat or controlling probe inputs). All outputs are off in this state except that if the Post-Circulate time is set to continuous, the pump will be on. When the heat request is received, the system moves to the Pre-Circulate state.

•Pre-Circulate:

The yellow LED is turned off and the green "Running" LED is turned on. The green LED will remain on for all other states except the fault states. If enabled the powered vent and the IRI gas valve are turned on. A command is sent to all active stages to cold purge the system. Cold purging clears out any combustion gas that may be in the combustion chamber. When purging is complete the system moves to the Heat State.

•Heat Stages 1-2-3-4:

The system will command the FCB micros to start their heat sequence starting with stage 1. Stage 2, 3, 4 will be activated in order based on an algorithm that determines how much heat is needed. The system will remain in this state until the heat request is satisfied, the Tstat is opened, or a fault occurs.

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