Resistance Termination For Comm3 Links; Fiber-Optic Wiring For Comm3/Comm4 Links - Trane TRACER SUMMIT Hardware And Software Installation

Table 6. Termination resistor placement for Comm3 links
Configuration type
0–800 ft (0–244 m)
Daisy-chain 800–2,500 ft (244–762 m)
> 2,500 ft (762 m)
Any length
Branch
BMTX-SVN01C-EN

Resistance termination for Comm3 links

Under certain conditions, a termination resistor needs to be placed on the
last device on a Comm3 communication link. Electrical resistors drop the
voltage of the current flowing through the wire so that electrical noise is
absorbed. The configuration and the wire length determines whether a
resistor is needed and how much resistance needs to be provided (see
Table 6).
Wire length
270–330 Ω
Not required
100 Ω
270–330 Ω, if needed

Fiber-optic wiring for Comm3/Comm4 links

Fiber-optic cable is used for Comm3 and Comm4 applications involving
long distances, inter-building cabling, and areas with a potential for high
electrical noise because there is little degradation of optic signals. The
integrity of an optic signal is maintained in the presence of several
sources of electrical noise, including lightning, EMI/RFI, voltage conduc-
tors, and ground loops.
Trane requires duplex, 62.5 μm core glass fiber-optic cable with ST con-
nectors, which comes in a variety of types for specific applications, such as
indoor, outdoor, burial, aerial, and duct. You can order fiber-optic cable,
fiber-optic modems, ST-type crimp connectors, epoxy connectors, and
other accessories from approved suppliers in the Trane Buying Group.
IMPORTANT
Trane recommends that only qualified fiber-optic technicians prepare
the fiber-optic end connectors and cable run lengths. Improper methods
may result in faulty communication due to signal degradation (decibel
loss). The signal degradation must be less than 14 dB on each fiber.
Fiber-optic modems
A fiber-optic Comm3 or Comm4 communication link uses EIA-485 data
transceivers (IFS D1300) and EIA-485 data repeaters (IFS D2300), which
are referred to as fiber-optic modems. These modems convert the electri-
cal signals from a twisted pair of wires to optical signals, which are sent
over the fiber-optic cable. At the other end, the optical signals are con-
verted back to electrical signals and sent along the twisted pair of wires.
The D1300 has one fiber-optic port and one twisted-pair (EIA-485) port.
The D2300 has two fiber-optic ports and one twisted-pair (EIA-485) port.
Comm3/Comm4 wiring
Resistance Resistor placement
On the last device of link
N/A
On the last device of link
On the devices at the
end of each branch
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