Chapter 5 UCM Wiring and Addressing
126 BMTW-SVN01F-EN
VariTrane DDC/VAV UCMs Interface
Description
The VariTrane direct digital control/variable air volume (DDC/VAV)
UCMs (UCM I, UCM IA, UCM II, UCM III, and UCM IV) allow a Tracer
Summit system to monitor and control all models of the VariTrane DDC/
VAV boxes.
You can connect these units to any non-isolated Comm3 UCM communi-
cation link on TB2. The link provides a serial communication interface
between the BCU and each DDC/VAV in the system. For specific informa-
tion about the number of VAV I, II, III, or IVs allowed per BCU and per
communication link, refer to Table 7 on page 46. VAV I and VAV IA
UCMs reside on different communication links from VAV II, VAV III, and
VAV IV UCMs.
Type of Communication Card
VariTrane UCM I and UCM IA use the non-isolated Comm3 card. Soft-
ware setup refers to VariTrane UCMI and UCMIA as VAV I. Refer to
“Non-Isolated Comm3 Card” on page 50.
VariTrane UCM II, UCM III, and UCM IV use the Comm4 card. Software
setup refers to VariTrane UCM II, UCM III, and UCM IV as VAV II/III/
IV. Refer to “Comm4 Card” on page 51.
Wiring Notes
To establish wiring connections between the UCM and the BCU, Trane
requires that you use the communication-link wiring specified in this-
manual. For wire selection specifications, see “UCM Communication-
Wire Characteristics” on page 55.
Use fiber-optic modems for building-to-building communication. If fiber
optics are not used, building-to-building communication wiring requires a
Transtector transient protector at each building. You can purchase Tran-
stector protectors through Trane. Contact your local Trane sales office for
details.
In a daisy chain configuration, use one pair of wires that start at the BCU
and go to all UCMs in a continuous loop. A branch configuration is possi-
ble if you need to tap into a daisy chain. Limit the total aggregate length
of the wiring for each communication link to 5,000 ft (1,524 m).
To connect communication wiring:
1. Attach one end of the communication-link wiring to TB2 on the BCU.
For the location of TB2, refer to Figure 16 on page 47.
2. Attach the other end of the communication-link wiring to the VAV
communication terminal. Refer to the VAV UCM literature for con-
nection points.
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