A.O. Smith 650, GB/GW-300, 500, 750 SERIES warranty Description of CCB control states

The operation of these parts is described below:

UIM Screens:

On all screens a double vertical bar appears on the right side of the display each time a key is touched to indicate that a key has been activated. On several screens an indicator ">" appears on the left side of the display to indicate the active line. The "Up/ Down" keys are used to move the indicator to the desired line and the "Select" key is pressed to select the line. Also, on most of the screens, up/down arrows appear on the right side of the screen to indicate that there are additional lines either above or below the displayed four lines.

•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 LW/CO, 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, LW/CO, 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 respective 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)

•High Speed Blower Prover - when the High Speed Blower is on.

•Low Speed Blower Prover - when either the High or Low Speed Blowers are 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 software that the CCB and FCB micros are in. The CCB has 8 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 1-4 when a call for heat is initiated. Once heat has been satisfied or the Total 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 and 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