Purpose
This article will cover a common scenario where a technician needs to determine what’s controlling programable output on a UC or Symbio control. In the example below, we will review how to determine what is controlling a binary output for a Reheat Liquid Line Valve.
In Tracer TU, the current value is showing off.
Double clicking on the Reheat Liquid Line Valve text area will open an Override Request window.
This window provides valuable information about the output. The screen shot above shows that the output has two owners telling the output to be in the off state. The owner with the lowest value priority determines the output of the controller. In the example above, BACnet will override the TGP2 output.
Hot_Gas_Reheat = this is the name of the TGP2 program writing to the output.
BACnet or MODBUS = indicates the value is being override by a system controller (Trane or 3rd party) or an External BACnet Referencers – Trane Commercial HVAC Help Center
When custom outputs and values (analog or binary) are configured, BACnet system controllers can write to any points. For proper operation, BACnet should only write to points designated with ‘BAS’ in the point name (ei. BAS Discharge Air Setpoint).
BACnet devices can be renamed at the system controller and if a renamed device is writing to a control, it won't appear as BACnet as shown above. To determine if a value is being written by TGP2 or a BACnet device, go to Utilities > TGP2 Editor.
This will open a new window and as default will show the list of available programs on the right (see below). If the program list doesn't show as default, select View > Display Program List to show the list.
If the owner name shown in the Override Request window isn't shown on the Program List, a renamed BACnet device is writing to the point.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.