Unit Operating Limits

The purpose of this section is to describe those control features which are standard on all of the VAV and constant volume Self-Contained units.

Unit Switch

The SeIf-Contained unit is provided with a unit switch to set the control mode of the unit. This switch is located on the front panel of the unit control module and is accessible without opening the control panel door or removing any unit panels. The switch has three positions:

AUTO LOCAL — With the switch in this position, the unit operates as a stand-alone unit. The unit is controlled by the internal unit control module in response to sensor inputs. With the switch in this position, if the unit is tied to a Tracer^®, the Tracer can access the unit and read data but cannot override local control.

AUTO REMOTE — With the switch in this position, the unit still is controlled by the internal unit control module, but can interface with the Tracer (if the ICS interface control is provided) to override local control. It can also interface with a generic BAS system. Refer to page 16 for further descriptions of these control options.

STOP/RESET — With the switch in this position, all unit control functions, and thus unit operation, are shut down. This function sets all outputs to their de-energized state. All unit control module internal information is set to its initialized value, except for diagnostic information, which is not cleared until the unit is switched back into the Auto mode.

The unit is manually reset whenever the switch is moved to the Stop/Reset position from either the Auto/Local or Auto/Remote switch position. The unit is also reset whenever power is applied to the unit control module. In this case all diagnostic information is reset.

Digital Display

The unit control module contains a digital display to show operating conditions, setpoints, and diagnostics. The display is located on the front panel of the unit control module and is visible without opening the control panel door or removing any unit panels. Refer to Figure 13-1 for operating and diagnostic code list.

An advance display button is included to step through the operating codes, diagnostic codes, and setpoint display.

The unit normally displays the current operating mode continuously. However, when a malfunction exists which causes the entire unit to shut down, the display will alternate between the operating code at the time of failure and the last diagnostic code. When a malfunction exists which does not shut down the entire unit, the operating code will flash to indicate that a failure has been detected.

Operating States and Diagnostics List Diagnostics

Refer to Figure 13-1 for a detailed list of the diagnostic codes.

The unit control module will retain a diagnostic code history. The codes can be read on the display by using the display advance button. The computer diagnostic codes are intended to inform operators or maintenance personnel of unit malfunctions. Some of these malfunctions require manual reset to re-enable unit operation and clear the diagnostic code.