Trane LO manual Terminal Unit Control TUC, Fresh Air Damper Open, Probable Cause, Explanation

Terminal Unit

Control (TUC)

Table 50. Fresh Air Damper Open

Probable Cause	Explanation
Normal Operation	· The two-position fresh air damper opens under normal unit opera
	tion during occupied mode and closes during unoccupied mode.
	· Modulating analog and 3-wire floating point economizers open to
	the minimum position (configurable) when the unit is occupied and
	modulate to meet unit capacity requirements.
	· If the minimum damper position is zero, the damper may close
	for extended periods. During the unoccupied mode, the normal
	fresh air damper position is closed.
Override Present	The fresh air damper may be overridden open by either the Tracer®
	system or Everyware™ software. Whenever any override is active,
	the TUC drives the fresh air damper closed, unless the damper is
	concurrently overridden open.
Autocycle Test	The controller includes an autocycle test sequence that verifies
	analog and binary output operation and associated output wiring.
	However, the current test stage sequence may require the fresh
	air damper may be open. Refer to the “Autocycle Test” section on
	page 71.
Unit Configuration	The TUC cannot control fresh air damper outputs if the unit is
	configured for no fresh air damper. Also, if the fresh air damper type
	is incorrectly configured (on/off, modulating analog, or 3-wire
	floating point), it may not operate properly.
Wiring	The wiring between the controller outputs and the fresh air damper
	must be present and correct for normal damper operation. Refer to
	the typical unit wiring diagrams on pages 105-106.
Table 51. Zone Temperature Too Warm
Probable Cause	Explanation
Active heating/cooling	Verify that the active heating/cooling setpoints are reasonable. It is
setpoints	possible for either the zone sensor or for the Tracer® system to
	send heating and cooling setpoints to the TUC. Use the Tracer®
	system or Everyware™ software to determine which source is
	sending the setpoint.
Wiring	Verify the wiring of all end devices, such as valves and dampers.
	Use the manual overrides or the autocycle test to verify the end
	device operation.
Manual heat mode	If the Tracer® system places the TUC in manual heat mode, the TUC
sent by Tracer®	cannot switch to cool mode and therefore cannot provide cooling to
	the zone.
Zone sensor location	Locate the zone sensor in an area where the temperature is repre-
	sentative of the average zone temperature.

114 UNT-IOM-6