BMTX-SVN01C-EN 27
Chapter 4
BMTX BCU binary inputs
The BMTX BCU supports two binary inputs, which are wired to the ter-
mination board.
The inputs can be used for the following types of binary devices:
• Binary, including momentary contact switches (normally open), and
standard (maintained) switches
• Pulse meter (water, gas, and electric)
Common devices are enthalpy switches, differential-pressure airflow
switches, system shutdown switches, remote alarms, photocell, gas
meters, water meters, and electrical demand meters.
All devices connected to binary inputs must be isolated and have dry,
ungrounded contacts.
For pulse meter devices, the closure pulse rate may range from 0–4 Hz.
On a contact closure, the minimum contact dwell time must last at least
125 ms for the closure to be recognized by the input.
For all inputs, you must create and set up the necessary objects that will
provide units, calculation, and alarming to the desired input. Refer to the
System Programming guide for creating and setting up these objects.
Input wiring guidelines
Input wiring must meet the following guidelines:
• All wiring must conform to national and local electrical codes.
• Input wiring should not exceed a length of 1,000 ft (305 m). If the rec-
ommended lengths are exceeded, the wire may pick up EMI/RFI,
which might affect operation of the BMTX BCU input.
• Use only 18–22 AWG (1.02–0.643 mm
2
), twisted-pair wire with
stranded, tinned-copper conductors.
• Do not run input wires in the same wire bundle with high-voltage
power wires. Running input wires with 24 Vac power wires is accept-
able, but the input wire must be shielded.
• Terminate input wires before installing the main circuit board (see
“Connecting the main circuit board” on page 23).
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