Trane LO Terminal Unit Control TUC, Troubleshooting, TUC Does Not Communicate, Probable Cause

Terminal Unit

Control (TUC)

Troubleshooting

		More detailed information about programming and operating the TUC
		board can be found in Trane publication, EMTX-IOP-1TUC Installa-
		tion Operation and Programming Guide.
	Table 44. TUC Does Not Communicate
	Probable Cause	Explanation
	TUC is not addressed correctly	Verify the ICS address according to Table 21 on page 63. Each TUC
		on the link requires a unique address in the range of 33 to 96. Set or
		modify the DIP switches, then short the TUC test input momentarily.
	Incorrect comm 4 wiring	Verify that the link is twisted pair Trane part # 400-20-28 or equiva-
		lent. TUC (comm 4) wiring is polarity sensitive throughout the com-
		munication link. If possible, isolate the TUC from the rest of the ICS
		link to determine if the problem exists in the comm wiring or in the
		TUC board.
	Defective TUC board	If the previous solutions do not fix the problem, it may be necessary
		to replace the TUC board.
Table 45. Fan Outputs not Energizing
Probable Cause		Explanation
Random start enabled		When enabled, the random start feature delays the unit start-up for
		3 to 32 seconds (configurable) after power-up.
Power-up control wait		When enabled, the power-up control wait feature delays the TUC
		startup for two minutes after power-up. This delay allows the
		Tracer® system ample time to communicate its fan control request.
Cycling fan operation		When configured to cycle with capacity, the unit fan cycles off when
		there is no call for heating or cooling. The heating/cooling sources
		cycle on or off periodically with the unit fan to match the capacity
		according to pulse-width-modulation (PWM) logic.
Unoccupied operation		The fan cycles with capacity when the unit is in unoccupied mode.
		This occurs even if the unit is configured for continuous fan opera-
		tion. While unoccupied, the fan cycles on or off with heating/
		cooling to match the capacity according to pulse-width-modulation
		(PWM) logic. The TUC can be placed in unoccupied mode either
		through a Tracer® system or through BIP3 if it has been configured
		as occupied/unoccupied.
Latching diagnostic present		A specific list of diagnostics effects fan operation. For more informa-
		tion, see the “Diagnostics” section on page 73. Latching diagnostics
		require a manual reset to restore normal unit operation.
Unit disabled		The Tracer® system can disable the unit via a shutdown input or
		BIP1 can be configured as external interlock.
Local fan switch: off		Using the local fan mode switch to determine fan operation, the
		“off” position on the switch controls the unit fan to off.

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