A.O. Smith VB/VW- 1000, VB/VW- 750 HighLimitDifferentialSetpointAdjustment Procedure

Use the following procedure to change the automatically resettable High Limit Setpoint:

1.Press the MENU key.

2.Scroll the “>” with the DOWN key next to USER SETTING SCREEN.

3.Press the SELECT key.

4.Scroll the “>” with the DOWN key until it is pointing to HIGH

LIMIT SETPOINT.

5.Press the SELECT KEY.

6.Use the UP and DOWN key to select the value you wish to enter.

7.Press the SELECT key to accept and store the new value.

•High Limit Differential:

The outlet temperature must be below the automatic High Limit setpoint minus the High Limit Differential setpoint before a call for heat can be generated.

HighLimitDifferentialSetpointAdjustment Procedure

The High Limit Differential Setpoint has a range of 1°F to 50°F for all models. Use the following procedure to change the High Limit Differential Setpoint:

1.Press the MENU key.

2.Scroll the “>” with the down key next to USER SETTING

SCREEN.

3.Press the SELECT key.

4.Scroll the “>” with the DOWN key until it is pointing to HIGH

LIMIT DIFFERENTIAL SETPOINT.

5.Press the SELECT key.

6.Use the UP or DOWN key to select the value you wish to enter.

7.Press the SELECT key to accept and store the new value.

• Operating Differential Setpoints:

Each of the two stages has an independent Operating Differential setpoint.

•Temperature Units:

Temperature can be displayed in either °F or °C units.

•Post Circulate Delay Time:

The time circulation pump will stay on after the burner is turned off. The time in seconds is adjustable with the following values: 45, 90, 180 or continuous. If the continuous value is selected the pump will remain on at all times and the post circulate state time will be set at 45 seconds.

•Network Address:

This is a unique number assigned to this boiler to differentiate it from other boilers or water heater on the same A. O. Smith proprietary network. A valid Network Address can be any number from 1 to 31. It is set by default to zero, which is an invalid address. The boiler will not communicate until it is changed to a valid and unique number. This prevents two units from trying to respond to the same request from the PC or supervisory network device.

•Configuration Settings Screen:

Displays the status of the dipswitches installed on all boards as described earlier.

•Log & System Info Screen: Displays the following information:

Elapsed hours of operation (Total time system has been powered up)

Number of running minutes (Number of minutes system has been in the run mode)

kBtu rating of the boiler (0 to 5750kBtu in 10kBtu increments)

The software revision level of the MCB.

•Current Error Screen:

Displays the last error that the system has detected plus a time stamp of when the error occurred. (The time stamp is based on the elapsed hours value at the time the error occurred. It is displayed in hours and minutes. This error remain displayed as long as it is still valid. When cleared it is moved to the Error History Screen. The system will automatically jump to this screen when an error is detected. It will also go to this screen upon power-up if an error was still valid when power was turned off.

NOTE: Errors are cleared from this screen by pressing the “select” key.

•Error History Screen:

This screen displays a list of the last 9 errors (with time stamps) that have occurred. The last error to occur is displayed first. If a new error occurs this screen is presented to display the error.

•Reload Defaults Screen:

From this screen the user can restore the factory default values for screen adjustable configurations by pressing the Select key. The values restored are as follows:

VW Models

Oper Setpnt (Operating Setpoint) - 145° F (63° C) Hi Limit (High Limit Setpoint) = 210° F (99° C)

Hi Limit Dif (High Limit Differential) = 20° F (11° C)

VB Models

Oper Setpnt (Operating Setpoint) = 190° F (88° C) Hi Limit (High Limit Setpoint) = 230° F (110° C)

Hi Limit Dif (High Limit Differential) = 20° F (11° C)

Both Models

Tempert Units (Temperature Units) = F

Post Cir Secs (Post Circulation pump delay = 45 seconds Network Address (Network Address) = (none)

UIM Touch Switches

Below the LCD display are five touch switches or keys, that the operator uses to operate the system.

•Menu Key:

Pressing this key activates the menu screen where the other screens can be accessed.

•Select Key:

This key performs several functions. Screens can be selected from the menu screen by pressing this key when the “>” appears next to the screen desired.

On the User Settings screen items that appear next to a “>” symbol can be selected with this key. If a setpoint configuration item is selected, the “>” will then flash slowly to indicate that the item has been selected. The Up and Down keys are then used to change its value.

From the Current Error Screen this key is used to reset the system from an error:

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