Honeywell BACnet Installation Instructions

BACnet® Fixed Function Thermostat

MERCURY NOTICE

CAUTION

FOR FAN COIL/HEAT PUMP/CONVENTIONAL SYSTEMS

INSTALLATION INSTRUCTIONS

APPLICATION

Honeywell’s BACnet® Fixed Function Thermostat, BACnet
FF, is a configurable device with 19 pre-loaded
applications. The thermostat is a communicating,
intelligent sensor-controller combination with built-in
temperature and humidity sensors used to control
systems such as roof top units, fan-coil units and heat
pumps. The thermostat communicates over an MS/TP
LAN so it operates as a fully-functioning BACnet
controller and easily integrates with the building
automation system. The two available models are
TB3026B and TB3026B-W, which includes a wireless
sensor option.

INSTALLATION

Dimensions

The Fixed Function Thermostat consists of a mounting
plate and a circuit board with a plastic cover.

Fig. 1. Fixed Function Thermostat dimensions.

When Installing this Product...

1. Read these instructions carefully. Failure to follow

them could damage the product or cause a
hazardous condition.

2. Check ratings given in instructions and on the
product to ensure the product is suitable for the
application.

3. Installer must be a trained, experienced service
technician.

4. After installation is complete, check out product
operation as provided in these instructions.

If this control is replacing a control that contains
mercury in a sealed tube, do not place your old
control in the trash. Dispose of properly.

Contact your local waste management authority
for instructions regarding recycling and the proper
disposal of an old control. If you have questions,
contact Honeywell Customer Care Center.

Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.

Disconnect power supply before installation.

31-00093-03

BACNET® FIXED FUNCTION THERMOSTAT

CAUTION

4 FEET

(1.2 METERS)

YES

NO

NO

NO

M36229

20
19
18
17
16
15
14
13
12

11

M36230

10

9

8

7

6

5

4

3

BO-5

BO-4

BO-3

BO-2

GND

AO-0

COM

AO-1

MS TP

+

MS TP

–

24VAC = HOT

RELAY
24VAC

BO-0

BO-1

GND = NEUTRAL

AI/BI-0

COM

AI/BI-1

COM

AI/BI-2

Location

Do not install the thermostat where it can be affected by:
— drafts or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall

behind the thermostat.

IMPORTANT

To avoid electrical interference, which can cause
erratic performances, keep wiring runs as short as
possible and do not run thermostat wires adjacent
to the line voltage electrical distribution systems.
Use shielded cable. The cable shield must be
grounded only at the controlled equipment case.

WHEN USED TO SENSE ROOM TEMPERATURE

Install the thermostat about 4 ft. (1.2m) above the floor in
an area with good air circulation at average temperature.
(See Fig. 2.) Confirm mounting height meets Americans
with Disabilities Act requirements.

WHEN NOT USED TO SENSE ROOM TEMPERATURE

When using the remote-mounted temperature (and
humidity) sensor(s) to sense ambient conditions, install
the thermostat in an area that is accessible for setting and
adjusting the temperature and settings.

Fig. 3. Wallplate dimensions.

Wiring the Wallplate

IMPORTANT

All wiring must comply with local electrical codes
and ordinances.

NOTE: Maximum (and recommended) wire size is 18-

gauge. Do not use wire smaller than 22-gauge.

Follow equipment manufacturer wiring instructions when
available. A letter code is located near each terminal for
identification.

Power must not be connected while wiring.

Wiring a unit that is powered may result in
electrical shock and/or equipment damage.

Mounting Wallplate

The thermostat can be mounted horizontally on the wall or
on a 4 in. x 2 in. (101.6 mm x 50.8 mm) wiring box.

1.

2. Use a pencil to mark the mounting holes (see Fig. 3).

3.

4. Pull the wires through the wiring opening, and posi-

5. Insert the screws into the holes and tighten.

31-00093—03 2

Fig. 2. Typical location of thermostat

or remote-mounted sensor.

Position and level the wallplate (for appearance only).

Drill two pilot holes in the wall, on the marks. For dry­wall, drill 3/16-in. holes. For firmer material such as
plaster, drill 7/32-in. holes. Gently tap anchors (pro­vided) into the pilot holes until flush with the wall.

tion the wallplate over the mounting holes.

1. Connect wires to the terminal blocks. See Fig. 4 for
terminal assignments and Table 1 for terminal
descriptions.

2. Securely tighten each screw.

3. Push excess wire back into the hole.

4. Plug the hole with non-flammable insulation to pre-

vent drafts from affecting the Fixed Function Ther­mostat.

5.

Check for loose or frayed wire that may cause a short.

Fig. 4. Fixed Function Thermostat terminal

assignments.

BACNET® FIXED FUNCTION THERMOSTAT

WARNING

Do not apply line voltage to source pins.

A jumper is pre-installed between pins 1 and 2. The
jumper supplies 24 VAC to BO-1, BO-3, and BO-4 relays. It
can be removed if those BOs are powered from an external
source. (Note: BO-0, BO-2, and BO-5 relays are powered
from terminal 1.)

See BACnet Fixed Function Thermostat System
Engineering Guide (31-00098) for typical wiring
examples.

Table 1. Terminal Identification.

Terminal Label Connection

1 24VAC 24 VAC Power

2 RELAY 24VAC 24 VAC Power

3 BO0 Relay Output

4 BO1 Relay Output

5 GND Ground

6 AI0 Universal Input

7 COM Common

8 AI1 Universal Input

9 COM Common

10 AI2 Universal Input

11 MS/TP - BACnet ® Communications

12 MS/TP + BACnet ® Communications

13 AO1 Analog Output

14 COM Common

15 AO0 Analog Output

16 GND Ground

17 BO2 Relay Output

18 BO3 Relay Output

19 BO4 Relay Output

20 BO5 Relay Output

Table 2. MS/TP LAN Facts.

Tra nsm ission
speed

Layout Bus (daisy chain).

Cabling BACnet specifies the following. Shielded,

Segment
length

Maximum
devices
overall

Maximum
devices per
segment

Repeaters Required when making runs longer than

Ter min ating
resistors

Shield
grounding

9.6, 19.2, 38.4, 76.8Kbps (configured at
global controller).

twisted-pair cabling with characteristic
impedance between 100 and 130W.
Distributed capacitance between
conductors must be less than 30 pF/foot
(100 pF/m). Distributed capacitance
between conductor and shield must be
less than 60 pF/foot (200 pF/m). Foil or
braided shield acceptable.

4000 ft. (1071 m.) per segment using
recommended wire.

Depends on classification of devices as
master or slave. Maximum number of
master devices is 128. Maximum number
of slave devices or devices overall (mixed
master and slave) is 255. This includes
BACnet FFs, BACnet global controllers (all
are considered masters) and any other
devices, regardless of their relative unit
loads.

Depends on relative unit load of devices
(see “Terminating MS/TP LAN Cabling” on
page 3).

4000 ft. Three repeaters maximum
between any two devices.

Matched resistors required at each end of
segment bus wired across (+) and (–). Use
matched precision resistors rated |
1/4 W ±1% / 80 - 130 Ohms.

Ground shield drain wire at single point
earth (panel) ground, not BACnet FF
ground. Tape off shield drain wire at other
end. Tie shield drain wire through at each
BACnet FF.

MS/TP LAN Wiring

The BACnet FF communicates on the site-wide BACnet
system over a twisted-pair MS/TP LAN, which uses the
EIA–485 signaling standard. The BACnet FFs are master
devices on the MS/TP LAN.

Each BACnet FF employs a high-quality EIA–485
transceiver and exerts 1/4 unit load on the MS/TP LAN.

Terminating MS/TP LAN Cabling

MS/TP terminations are located on the lower left of the
BACnet FF wallplate.

Maintain polarity of the MS/TP wire run throughout the
MS/TP LAN.

Grounding the MS/TP LAN Shield

Proper shield grounding of the MS/TP cabling can help
minimize the risk of communications problems and
damage to equipment because of transient voltage spikes
(for example, lightning strikes).

Follow these guidelines for grounding MS/TP cable
shields:

• Each MS/TP segment should have a single point of
shield ground, preferably as close to the middle of the
cabling run as possible.

• Do not ground the MS/TP shield using a BACnet FF
terminal.

3 31-00093—03

BACNET® FIXED FUNCTION THERMOSTAT

CAUTION

• Never ground both ends of a shield; differences in
potential between the grounds may induce current on
the shield, causing interference.

• At termination connecting points, tie the shield through
with a wire nut.

• At ungrounded, exposed shield points (the end of a
segment), tape back the shield to the wire jacket or, for
optimum transient shunting, use 100V gas discharge
tubes or 120V MOVs between shield and ground.

Terminating Resistors

Matched terminating resistors wired across MS/TP+ and
MS/TP– are required at the last device on each end of the
MS/TP segment for signal integrity (Fig. 5).

Optimum segment performance typically requires
“tuning,” a process by which the value of the terminating
resistors is selected based on the wave form of signals on
the segment. View wave forms using an industrial scope
meter. The goal is to have as square a wave form as
possible with an amplitude greater than 200 mV. Resistors
affect the wave form as follows:

• When the resistance value decreases, the amplitude of
the wave form decreases and becomes more square.

• When the resistance value increases, the amplitude of
the wave form increases and becomes less square.

WALL

INSTALLATION

REMOVE DURING

Fig. 6. Thermostat mounting.

M19919

Typically, precision resistors in the range 80-130 Ohms
(+1%) yield acceptable results. Ideally, the value of the
terminating resistors should match the rated
characteristic impedance of the installed cable. For
example, if the installed MS/TP cable has a listed
characteristic impedance of 100 Ohm, install 100 Ohm
matched precision resistors.

Do not mismatch terminating resistors.

Ensure that both resistors on a segment have the
same value.

NOTE: Typically, White is Data - and Black is Data +.

Fig. 5. Terminating resistor detail.

Mounting Thermostat to Wallplate

1. Align the terminal screw blocks with the pins on the

back of the thermostat.

2. Push the thermostat straight onto the wallplate.

NOTE: To remove the thermostat from the wall, first pull

out at the bottom of the thermostat; then remove
the top.

CONFIGURATION

Once the BACnet FF is mounted and wired, it can be
configured using the local touchscreen and a
configuration wizard using Niagara Framework® software.
When using the software, BACnet data is transmitted to
and from the device and building management system
using analog values (AVs) and binary values (BVs).
Listings of these AVs and BVs can be found in their
entirety in the BACnet Fixed Function Thermostat System
Engineering Guide (31-00098) and a limited listing can be
found on page 6.

Adjusting the Date and Time

When the controller is first powered up, the date and time
might need to be set. These are set at the factory, but the
on-board power supply may have run down. If this
happens, adjust the date and time.

TO ADJUST THE TIME

1. Touch Clock at the bottom of the screen.

2. Use the arrows to adjust the year, month, and day.

3. Press DONE.

4. Adjust the time and press DONE.

Setting the MAC Address and Device Instance

The MS/TP MAC address for each device must be set to a
unique value in the range of 0-127 on an MS/TP network
segment. The MAC address is set using the installer setup
menu through the device’s display. The factory default
MAC address is 0.

31-00093—03 4