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.

UNT-IOM-6

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Page 109
Image 109
Trane LO manual TUC Does Not Communicate, Fan Outputs not Energizing Probable Cause Explanation

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