ACI-Automation Components BACnet DUCT SERIES Installation Instructions

BACnet DUCT SERIES

Installation & Operation Instructions

GENERAL INFORMATION

The BACnet Duct Series sensor is designed for use with

electronic controllers in commercial heating and cooling

building management systems. The ACI BACnet Duct

Series sensor can be ordered to monitor temperature, RH,

or temp/RH in commercial HVAC ductwork. It uses BACnet

MS/TP for physical connection to a BAS or controller, has

dip switches to set addresses and baud rate, and has on

board end-of-line termination. There is no analog output.

WIRING INSTRUCTIONS

The BACnet Duct Series temperature sensor has a
depluggable terminal block located on the front of the
PCB. For ease of wiring, we recommend removing the
block, wiring, and reattaching before mounting. 16 to 22
AWG two conductor shielded cable is recommended for
powering the sensors.

ACI recommends using Belden 3105 or compatible cable
for RS-485 communication wiring. This wire has 120 ohm
input impendence. The terminal blocks allow for (1) or (2)
wires to be connected in each position for daisy chaining.
Daisy chain the RS-485 wiring and do not use “Star” or “T”
wiring. Avoid running communication wires next to AC
line voltage wires. These can be sources of noise that can

aect signal quality.

FIGURE 1: ENCLOSURE DIMENSIONS

PLASTIC BOX (-PB): TEMP. ONLY

3.60"

(91.44 mm)

2.25"

(57.15 mm)

4.79"

(121.55 mm)

2.35"

(59.80 mm)

EURO (-EH): RH and RH/TEMP.

4.30"

(109.22 mm)

1.51"

(38.25 mm)

3.01"

(76.51 mm)

3.80"

(96.56 mm)

1.90"

(48.28 mm)

PRECAUTIONS

Remove power before wiring. Never connect or

•

disconnect wiring with power applied.

It is recommended you use an isolated UL-listed

•

class 2 transformer when powering the unit with 24
VAC. Failure to wire the devices with the correct
polarity when sharing transformers may result in
damage to any device powered by the shared

transformer.

Page 1

2.12"

(53.72 mm)

10.05"

(255.32 mm)

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PRECAUTIONS (Continued)

DO NOT RUN THE WIRING IN ANY CONDUIT WITH

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LINE VOLTAGE (24/120/230 VAC).

If the 24 VDC or 24VAC power is shared with devices

•

that have coils such as relays, solenoids, or other
inductors, each coil must have an MOV, DC/AC
Transorb, Transient Voltage Suppressor (ACI Part:

142583), or diode placed across the coil or inductor.
The cathode, or banded side of the DC Transorb or
diode, connects to the positive side of the power
supply. Without these snubbers, coils produce very
large voltage spikes when de-energizing that can
cause malfunction or destruction of electronic
circuits.

MOUNTING INSTRUCTIONS

For optimal readings, follow these tips:

FIGURE 2: LAYOUT

TERMINAL BLOCKS

V D-GN
POWER

23618421421

4
6

ADDRESS BAUD

D+

BACNET

RESET BUTTON

LED

END OF LINE
TERMINATION

DIP SWITCH

EN DIS

The sensor should be mounted in the middle of the

•

duct where air circulation is well mixed (no

stratication), and not blocked by obstructions.

Stratication and obstructions can cause sensing

errors. An example is downstream from a heating or

cooling coil.

Duct probe should be placed (3) to (4) duct

•

TABLE 1: WIRING CONNECTIONS

TERMINAL

BLOCKS

+V

GN

D-

D+

CONNECTIONS

Power Supply Positive 12-36VDC / 24VAC

Power Supply Common or Ground

EIA-485 Data Negative

EIA-485 Data Positive

segments down from any bend or obstructions

and away from 90° bends.

Mount the sensor on the top or sides of duct work; mounting on the bottom risks damage due to moisture.

•

The BACnet Duct Temperature-only sensor uses the Plastic Box (-PB) enclosure. Alternatively, the Euro (-EH) enclosure is

used for the BACnet Relative Humidity (RH) sensor and BACnet RH/Temperature Combo sensor (see FIGURE 1). Be sure to

follow the instructions listed for your enclosure.

PLASTIC BOX (-PB) ENCLOSURE INSTALLATION

Drill a 3/8” hole in the duct and insert the probe through the hole until the foam pad is tight to the duct.

Drill pilot holes for the (2) mounting screws. Use the enclosure ange as a guide, or use the dimensions listed on page 1 to
measure out.

Now fasten and insert (2) screws #8 x ¾” TEK (provided and recommended) through the mounting holes in the ange and
tighten until the unit is held rmly to the duct.

Refer to the wiring instructions (p. 2) to make necessary connections. After wiring, shut the cover of the enclosure.

*Reference FIGURE 2

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