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Terminal Unit
Control (TUC)
102 UNT-IOM-6
Use the human interface to read the unit operating machine state.
1. Read and record the initial TUC address.
2. Set the TUC DIP switch #5 and #8 to ON (address = 9). The
remaining switches will be off.
3. Short and hold the test input.
4. The LEDs will blink to define an operating machine state. The
operating machine state information will be displayed in a series
of three blink sequences.
Sequence 1: When the test input is shorted continuously all
LEDs go off for one second.
Sequence 2: LED #5 will light to indicate that sequence 2 is
currently being displayed. LEDs one through four will display the
first part of the operating machine state.
Sequence 3: LED #6 will light to indicate that sequence 3 is
currently being displayed. LEDs one through four will display the
second part of the operating machine state.
5. Reference Table 25 on page 75 to interpret the operating machine
state derived from the blink sequences.
Table 40. Blink Sequence Corresponding Diagnostic Codes
Sequence 1 Sequence 2 Sequence 3
1 2 3 4 1 2 3 4 1 2 3 4 Code Diagnostic Latch
None Power failure None
None Controller failure None
¡¡¡¡¡¡¡¡¡¡¡¡ 00 None N/A
¡¡¡¡l ¡¡¡l ¡l l 8B Condensate overflow Yes
¡¡¡¡l ¡¡l l ¡l l 9B Leaving water temp No
sensor 1 failure
¡¡¡¡l ¡l ¡¡¡¡¡ A0 Zone and supply temp No
sensor failure
¡¡¡¡l l ¡¡l ¡¡¡ C8 High EWT No
¡¡¡¡l l ¡¡l ¡l l CB Low EWT No
¡¡¡¡l l ¡¡llll CF Low temp. detect. or Yes
condensate overflow
¡¡¡¡l l ¡l ¡¡ll D3 Low discharge air temp Yes
¡¡¡¡l l ¡l ¡l ¡¡ D4 Smoke alarm Yes/No
¡¡¡¡l l ¡l ¡l ¡l D5 High dischg air temp Yes/No
¡¡¡¡l l ¡lll¡l DD Low fresh air temp No
¡¡¡¡lllll¡¡¡ F8 Bad configuration No
¡¡¡¡lllllll¡ FE Return air high limit Yes
Reading the
Operating
Machine State