Smart temp SMT-131 User Manual

SMT - 131

Manual

Ver 2.1

Page 2

Revision History

Version 1 Original Document
Version 1.1 Added Mode select in Modbus
Version 2.0 Based on version 2 Hardware (firmware 3.0+)
Version 2.1 Added temperature calibration, DI logic and High fan limit.

Index

Index 2
Introduction 3
Thermostat operation 3
Installation - HVAC Control 4

DIP Switch Settings 5
Wiring – HVAC Control 5
0-10v Outputs 7
Belimo ™ 6 Way Valve 8
2 Pipe Mode 8
Ancillary Functions 9

Occupancy Detection 9
Doorbell 11
Outside Door Station 11
Modbus Wiring 12
Remote Temperature sensors 13
Installer Options Menu 13

Modbus Data – Addendum 1 16
Specifications 21

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Introduction

The Smart Temp SMT-131 thermostat has been designed for use in hotel rooms and other
locations where the user will require a thermostat that is simple to understand and functions in a
logical manner. Further, given the nature of the hospitality industry in general it is important that
the thermostat be very intuitive, robust and attractive. The SMT-131 thermostat has been
designed with these important goals is mind.

The SMT-131 also offers advanced energy conservation features such as set point limit control,
automatic un-occupied heating and cooling settings as well as Modbus RTU communications for
integration with the “Building Automation System” (BAS) or “Hotel Check In” system. Additionally,
the SMT-131 seamlessly interfaces with the Smart Temp OC-3D occupancy detection system and
HOT-242 “Door Station” system for added functionality.

Thermostat operation

The SMT-131 is an extremely simple
thermostat to operate and has been
designed to not require a user manual.

The diagram to the left shows all LCD
elements and the 7 buttons (Up / Down /
Make Up Room / Do Not Disturb / On – Off
(mode) / Fan Mode / Deg C-F Select.

Depending on switch and installer menu
settings not all LCD segments maybe
shown.

On/Off (Mode)

Tap the On/Off button to turn the thermostat On or Off and If permitted to select heat only or
cool only mode. (To ensure the simplest user operation on/off only Mode is set as default).
Note - for simplicity - If the thermostat is OFF by simply touching the thermostat display will turn
it on.

Set Temperature

Adjust the target temperature with the Up or Down button. The range of temperature
adjustment can be limited with the installer setting “heat and cool limit setting. (See page 14)

Fan

Single fan speed mode (Sw1=Off) (See Dip switch settings page 5)
Tap the fan button to cycle between auto fan and continuous fan mode.

Three fan speed mode (Sw1=On) (See Dip switch settings page 5)
Tap the fan button to cycle between low, medium, high and auto fan speeds. Press and hold the
fan button to turn the fan on continuously.

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Note. Option 16 in the installer menu (See page 15) permits you to set the SMT-131 to
automatically reset the indoor fan to Automatic Mode (cycle on and off with heating and cooling)
every time the thermostat is turned off and then back on if desired.

Ventilation Mode

If permitted by DIP Sw7, (See page 5) the user can run the indoor fan only (Ventilation Mode)
when the SMT-131 is off by tapping the fan button. Each tap of the fan button will cycle between
all available fan speeds.

“Make up Room” & “Do Not Disturb” Buttons
When enabled by DIP Sw8, (See page 5) pressing these buttons will activate relevant LCD
segments and backlight colour on the optional outside door station as well as write data to
Modbus for monitoring by a BAS system.

Installation - HVAC Control

System Design

Great effort has been taken to make the SMT-131 system intuitive,
reliable and easy to install. Using a common sense approach to the
installation will ensure this product is installed easily and to the

customer’s satisfaction. Please read and understand this instruction

manual so that installation, testing and commissioning process is
undertaken in an effective and efficient manner.

Opening Wall Controller

Open the SMT-131 wall controller by placing a flat blade screwdriver
or coin in the slot on the bottom of the thermostat case (1) and
gently twist (2) to release the case locking clip. Gently pry the two case halves apart at the base
taking care not to twist the case as this may crack the LCD.

Mounting wall Controller

The SMT-131 should be mounted in a convenient location at approximately 1.2 to 1.5 meters

from the ground. It should be located in a “typical” location where it will sense the accurate room

temperature and not be effected by direct sunlight or drafts.

It is highly recommended that any penetrations in the wall where wiring may pass for example be
sealed to prevent drafts entering the rear of the thermostat and effecting the room temperature
sensor.

Take care to ensure excess wiring is not trapped between the cases half’s when closing - push
excess wires into the wall cavity. Never press on the LCD when closing the SMT-131 as it may
crack. Always press on the SMT-131 plastic case only.

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DIP Switch Settings

Switch

Function

On

Off

Sw1

Indoor Fan Mode

3 Fan Speed

1 Fan Speed

Sw2

Equipment Type

Heat Pump

Heat Cool

Sw3

HP Mode (Sw2= ON)
HC Mode (Sw2=OFF)

Rev Valve Heat (B)
HE – Fan With Heat

Rev Valve Cool (O)
HG – No Fan In Heat

Sw4

2 / 4 pipe mode

2 pipe mode

4 pipe Mode

Sw5

Comp Protection Delay

5 Min Anti Cycle

Immediate Compressor start

Sw6

Not Used

Sw7

Ventilation Mode

Permitted

Not Permitted

Sw8

Door Station (Optional)

Fitted

Door Station Not Used

Note: The SMT-131 reads the switch settings on power up only. If you change any DIP switch
settings you must cycle power or press the reset button before these changes will take effect.

It is expected that only qualified people will make adjustment to these dip switch settings.
Knowledge of the HVAC system under the control of the SMT-131 is essential prior to making
adjustment to these DIP switch settings.

Caution Incorrect adjustment of these DIP switch settings could cause HVAC

equipment damage. This would NOT be covered by warranty.

Wiring – HVAC Control

Terminal Designations

Terminal

Function

C

24V Neutral

R

24V Active - This voltage is switched back through the relays

Hi

Indoor Fan High Speed (NOT Used in Single fan speed mode - Sw 1 = OFF)

Med

Indoor Fan Medium Speed (NOT Used in Single fan speed mode - Sw 1 = OFF)

Low

Indoor Fan Low Speed (Used in single & three fan speed mode)

Y

Compressor or Cool - (Based on Sw 2 setting)

W - O/B

Reversing Valve or Heat - (Based on Sw 2 setting)

A1 – Cool

0-10V Output for Cooling (Typically used to control modulating valves)

A2 – Heat

0-10V Output for Heating (Typically used to control modulating valves)

A3 – Fan

0-10V Modulating Output for Indoor DC Fan

Com – 0V

0V terminal - Used for 0-10V, sensor or digital inputs ground reference

A

Modbus Data A

B

Modbus Data B

SI

Remote temperature sensor input (Remote / average / Modbus data use)

DI

Digital (Switched input) for forced un-occupied or initiate doorbell function

WC

Window Contact - Forces SMT-131 OFF if window open > 5 min (Adjustable)

DS

Door Switch – Monitors room door status for occupancy detection (see page 11)

PIR

PIR ( Movement sensor) input for occupancy detection (see page 11)

The SMT-131 is powered by 24VAC and requires the 24VAC

active and neutral to be connected to the “R” (active) and “C”

(Neutral) terminals for the SMT-131 to function. The 24VAC
applied to the SMT-131 “R” terminal is switch back through

Page 6

the 2A relays to the equipment. Note the drawing provided here.

Caution - Although the SMT-131 is a robust device, wiring errors can potentially

damage the thermostat. This damage is NOT covered by warranty. Take care when
wiring 24V near sensor inputs or the Modbus communications terminals.

Note - When the SMT-131 calls heating or cooling the SMT-131 will drive both the relays and the
0-10V outputs simultaneously. This way the SMT-131 can call a circulating water pump via the
relays as it controls room temperature with the valves if needed.

Page 7

0-10v Outputs

To permit the control of modulating heating and cooling valves as well as variable speed DC fan
motors or variable capacity HVAC systems the SMT-131 has been fitted with 3 x 0-10V outputs.

The 0-10V outputs in the SMT-131 are PI (Proportional Integral) controlled. This control method
provides the most accurate and cost effective way to control heating and cooling valves by
ensuring set temperate are reached as quickly and efficiently as possible while reducing
temperature overshoot.

As the SMT-131 is fitted with both relays as well as 0-10V outputs to control HVAC systems there
may be some slight disparity between the thermostat display and the 0-10V outputs actions. The
SMT-131 displays the relay actions more than the actions of the 0-10V outputs on the LCD. In
most cases these are very closely matched however as the 0-10v outputs have the capability of
providing finer control than do the ON/OFF relays heating and cooling may have started slightly
before indicated on the display. This is true of the fan also.

A1 – Cool

This output is used to control a cooling valve.

A2 – Heat

This output is used to control a heating valve.

A3 – Fan

This output is used to control a variable speed
fan or a variable capacity AC system. If the fan
mode is set to Auto speed the 0-10V output will
vary between these two values based on
calculated demand. If the user selects LOW speed, the 0-10V output will be fixed at 3.3VDC, when
Medium speed is selected the 0-10V output will be fixed at 6.6VDC. High speed is set to 10VDC

The installer menu provides the following settings for the control of the three 0-10V outputs.

Span

This is the value where the output is at maximum value. It sets how aggressive the 0-10V will
move for a given temperature change. Range is 0-5C

Time Interval

Time interval sets the running average calculation time. The smaller the number the faster the 0­10V output will respond to room temperature changes. Range is 10 – 300 seconds.

Direction

Forward action 0V = 0% open and 10V = 100% open; reverse action sets 0V = 100% open and 10V
= 0% open.

Minimum Value

Rather than start the output at 0V, when the output is called it will immediately jump to this
value. It will then vary the output to maximum. When approaching set point the value will drop
from the minimum value to 0v in 1 step. This setting is particularly useful for fan control as it will
not permit the fan to run too slowly when close to set point.

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Maximum Value (Fan A3) output only
When controlling 0-10V fans sometimes it is necessary to limit the fan spped to reduce noise or to
protect ducting. The fan output has a high voltage limit setting so regardless of the user selected
speed (High, Medium or Low) or thermostat selected auto speed the 0-10V output will not exceed
this pre-set high limit.

These settings can be found in the installer menu (starting on page 14)

Belimo ™ 6 Way Valve

Belimo™ manufactures an actuator that is in full cooling at 2V, off at 6V and full heating at 10V.
To use this type of actuator with the Smart Temp SMT-131 you must enter the installer menu and
set valve type to “Belimo™ Mode”.
The heating 0-10v output only is used
in this mode

Information on the installer menu
can be found on page 13 of this
manual.

As with normal valves, the 0-10V
heating and cooling span settings in the installer menu scale the heating and cooling outputs.
Factory default is full heating and full cooling 1°C from set point. The heating and cooling span can
be adjusted independently to a maximum of full heating and full cooling 3°C from set point. The
output is linear.

Note When using “Belimo” ™ mode, both the A1 “cool” and the A2 “Heat” 0-10 output are used.

Both will provide the same output to the value. (The A3 “fan” output will remain unchanged and
can be used to control a DC fan our other device).

2 Pipe Mode

The SMT-131 can measure pipe temperature via a remote sensor wired into the SMT-131 Sensor
input terminals (SI and Com 0-10 input). Based on the pipe temperature, the room temperature
and the set point the SMT-131 will control either the heating or the cooling outputs to maintain
guest comfort. If mode selection is on, the SMT-131 will only permit the appropriate mode to be
selected based on the pipe temperature.

To use the SMT-131 in 2 pipe mode set DIP 2 OFF and DIP 4 to the ON position. Set Installer menu
option 26 “Si & Com 0-V” to option “3” – 2 Pipe Mode. (See page 15)

The pipe sensor needed for 2 pipe mode is the RS-1d sensor - available as an optional part from
Smart Temp or an authorised distributor.

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Ancillary Functions

The SMT-131 has a number of additional capabilities such as communications with Building
Automation systems via its Modbus communications port. The SMT-131 will automatically control
temperature set points based on occupancy of the room when a suitable door switch and
movement sensor is fitted. The SMT-131 can even automatically shut down the air conditioning
system if balcony doors or windows are left open when the optional door / window switch are
fitted.

When you wish indication of the room status and an integrated doorbell from the hall way
outside the room, the SMT-131 can be fitted with the optional “HOT-243” hall panel.

Complete System Overview

The SMT-131 is the hub of a
compressive room comfort and
energy control system. As shown in
the picture the SMT-131 accepts
door, window and PIR contact
inputs to automatically control
temperature set points. The HOT
243 wall controller mounted in the
hallway outside of the room
provides feedback of the guests
needs to housekeeping plus
provides a convenient button to
activate the SMT-131 internal door
bell.

Regardless of the need to control conferential HVAC systems, 2 or 4 pipe fan coils with
modulating valves the SMT-131 has the necessary outputs to achieve your control needs.

Occupancy Detection

The SMT-131 has sophisticated logic
that when connected to your choice
of movement sensors, door and
window switches will automatically
control the set point and mode of
the SMT-131.
Using part or all of the functions
described below are completely
optional. The SMT-131 will function
perfectly as a HVAC controller without the door, window or occupancy detection logic enabled.

DO NOT APPLY EXTERNAL VOLTAGES TO THESE INPUTS

Page 10

Window Contact

The window contact input (WC) is used to automatically disable the HVAC system if a window is
left open. This is done to prevent energy waste by trying to heat or cool an open room.

The SMT-131 window input can be set for a Normally Open (switch open when window is closed)
or normally closed logic (switch closed when window is closed). When the window is left open for
longer than the pre-set time (0 to 300 seconds) the SMT-131 will automatically turn OFF. The text
“OFF” will flash in the LCD to indicate that the remote window (or door switch) is holding the
SMT-131 in off mode. The wall controller will prohibit all changes.

The SMT-131 will automatically restart once the window is closed.

The Installer menu option 28 “Window Input Logic” and option 29 “Window Input Delay”
(page15) sets the window detection logic in the SMT-131.

Door Switch

The Door switch input (DS) is used by the SMT-131 for 2 functions.

1) To detect that the door has been opened and then closed to let somebody into or out

of the room.

2) To detect if the door has been left open.

The SMT door switch input can be set for a Normally Open (switch open when door is closed) or

normally closed logic (switch closed when door is closed). The Installer menu 30 “Door Input
Logic” and option 31“Door Input Delay” (pageError! Bookmark not defined.) sets the door

detection logic in the SMT-131.

Entering or exiting the room.

Once the door is opened and then closed the SMT-131 will begin its occupancy detection process
using the PIR input described below. Based on the outcome of this process the SMT-131 will
remain on and permit guest interaction with the SMT-131 (adjust mode and set point for
example), or switch to “un-occupied” mode where the SMT-131 will substitute the guest set point
and mode for the installer pre-set values.

Door Left Open

When the door is left open for longer than the pre-set time (0 to 300 seconds) the SMT-131 will
automatically turn OFF. The text “OFF” will flash in the display to indicate that the remote door
(or window switch) is holding the SMT-131 in off mode. This is done to prevent energy waste by
trying to heat or cool an open room.

The SMT-131 will automatically restart once the door is closed.

PIR input

A PIR (passive infra-red) movement detector can be directly wired to the SMT-131 “PIR” input. As
movement is detected by the PIR it will send multiple On/Off pulses to the SMT-131 every time it
detects movement. The SMT-131 using this data along with door switch data will determine the
occupancy status of the room and behave accordingly. Note, the PIR must be separately
powered, typically from a 12VDC supply.

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Automatic Occupancy Detection Logic

Automatic occupancy detection requires the door switch and PIR input to be wired and working.

When the door is first opened the SMT-131 instantly enters “Occupied Mode” where the SMT­131 will permit the guest to set their desired temperature and mode of operation. Once the door
is closed the SMT-131 will “look” for movement as detected by the PIR sensor wired to the PIR
input. If no movement is seen within the installer pre-set seek time (installer adjustable 1 to 15
minutes) the SMT-131 will enter “Un-occupied mode” where the guest’s temperature and mode
will be replaced with installer pre-set values. Should movement be detected within the installer
pre-set seek time the SMT-131 will LOCK into “Occupied Mode” and no longer rely on continued
movement within the room to remain in “Occupied Mode”. Next time the door is opened and
then closed again the SMT-131 will again begin its occupancy detection process.

Note - even when the SMT-131 is in “un-occupied mode” it will continue to use the PIR input to
determine room occupancy. For example - a couple may be staying in the room and one leaves
the room leaving the other asleep in bed. As the door closes the SMT-131 will seek movement
and when none is found it will enter “un-occupied mode. As the sleeper wakes and then moves
the SMT-131 will automatically re-enter “Occupied Mode” even though it may have been some
time since the door was closed.

Installer option “PIR Input Delay” (page Error! Bookmark not defined.) sets the PIR mode (On or
Off) and the seek time value (1 to 15 minutes).

Manual Occupancy Input

The DI (Digital Input) & Com 0-10 terminals within the SMT-131 can be used to instantly force the
SMT-131 into “Un-occupied Mode”. This input can be wired to a simple card reader or other 3rd
party system that may be pre-installed for room occupancy detection.

When the SMT-131 is in “Un-occupied Mode” the display will go completely blank except for the
words “Unoccupied” in the top left. If the optional HOT-243 hall way panel is installed its display
backlight will go out to let housekeeping know the room is empty. Modbus register 40004 also
indicates occupancy status.

Doorbell

A built in doorbell feature is included with the
SMT-131 thermostat. This is normally activated by
the optional outside door station as described
above or via Modbus data link. In circumstances
where this is not convenient the Digital Input (DI)
terminals can be reassigned as a doorbell
activation switch with the digital input options
detailed in the installer menu. (see page 15). Simply place a momentary volt free switch across
“DI” and Com “0-V” terminals to activate the doorbell. Once pressed, the doorbell will chime for
about 10 seconds.

Outside Door Station

When coupled with the optional
Smart Temp door station the guest
has the ability to set the room as “Do

Not Disturb”, call for housekeeping

or be alerted to visiting guests with a
pleasant doorbell chime. Hotel staff
are informed about the room status

Page 12

or guest’s needs by text information displayed on the door station LCD or the door station

backlight colours.

Connection between the SMT-131 and the hotel door station is cable fitted with RJ12 plugs.
Cables can be provided at additional cost at up to 15 metres maximum. Alternatively custom
cables can be produced. They are direct wired (not cross over).

When fitting the door station, the SMT-131 DIP Sw8 must be ON. The outside door station will
flash all LCD segments if DIP Sw8 is in the wrong position.

Modbus Wiring

Modbus communications unlock many additional functions within the SMT-131 thermostat. It
also permits all modes, functions and controls to be remotely supervised and adjusted from a
central location if needed. Modbus object data can be found on page 13 of this manual.

The SMT-131 uses a high powered Maxim chipset that will “theoretically” permit the connection
of up to 255 devices on a single Modbus node. RF noises and other interferences will reduce the
real world permitted connections to a maximum of 150 ~ 200 in most cases.

Modbus and other communication protocol rely on the quality of cable and good installation
practises to ensure reliable communications. Modbus requires the use of screen cable with the
drain grounded in a single location.

When using a common power supply or when using a modbus master that also powers the SMT­131, ensure the R (24v active), C (24v common) Data A & B wires are not crossed.

Hint! When the SMT-131 is connected to a working Modbus Network and receiving valid data,
the decimal point in the temperature display will blink. If there is no communication or the SMT­131 is receiving corrupted data, this decimal point will remain on steady.

The Modbus data is provided in Addendum 1 at the back of this manual. (page 16).

Modbus relies on a series connection and

will normally not tolerate “Star” wiring or
“T” branches.

Page 13

Remote Temperature sensors

Occasionally the room thermostat cannot be installed
in the ideal location to measure the room
temperature accurately. In these circumstances the
SMT-131 can use optional remote temperature
sensors. These are a two wire device, not polarity
dependent and simply wired into the SMT-131 sensor
inputs terminals (“SI” and “Com 0-V”). Depending on
installer menu sensor settings, (shown on page 15),

remote sensor(s) will either override the SMT-131
onboard sensor or average with the onboard sensor.

Multiple sensors can be used for averaging over larger
areas if necessary.

Wireless (RF) remote sensors are also available if fixed
wiring cannot be installed economically.

Installer Options Menu

The SMT-131 has an impressive list of options that can be installer selected. These options tune
the thermostat’s performance as well as set energy conservation settings. This menu is
deliberately hidden and difficult to enter to discourage unauthorised tampering.

The information card provided in the SMT-131 box provides details on how to enter the SMT-131
menu. If this is lost please contact Smart Temp or an authorised distributor for support.

Navigating Through the Installer Mode Settings

The bottom right button steps forward through the menu options, the bottom left button steps
you backwards.

Adjust your options with the up/down buttons.

The current menu option is shown between the left and right
buttons. The example to the right shows option 3, select deg C
or F display.

Exit the menu saving changes by pressing and holding the bottom right or wait 3 minutes and the
SMT-131 will automatically exit the installer menu.

Page 14

Option List Table

Option

Setting

0

Buttons Shown

0: Both mode and fan buttons show (default)
1: Show mode but fan button hidden
2: Show fan but mode button hidden
3: Both mode and fan buttons Hidden

1

Permitted Modes

0: Off / Auto
1: Off / Auto / Heat / Cool
2: Off / Heat /Cool
3: Off / Heat
4 Off / Cool
5: Off / Auto (Display current heating or cooling mode)

2

Room / Set display

0: Show room and set temp (default)
1: Show set temp only

3

Native display format

0: C (default) 1: F

4

C/F button shown on LCD

0: Off(default) 1: On

5

High temp set limit

5C-30C/41F-86F

6

Low temp set limit

5C-30C/41F-86F

7

Dead band

0C-5.0C/0F-10.0F 0.1C/0.1F steps
Data format : Dead band * 10

8

Fan Purge Period

0: OFF
1: Fan purge - 1 min
2: Fan purge - 3 min
3: Fan purge - 5 min
4: Fan purge - 10 min
5: Heat only fan purge - 1 min
6: Heat only fan purge - 3 min
7: Heat only fan purge - 5 min
8: Heat only fan purge - 10 min
9: Cool only fan purge - 1 min
10: Cool only fan purge - 3 min
11: Cool only fan purge - 5 min
12: Cool only fan purge - 10 min

9

Fan span (3 speed relays)

0.5C-3.0C/1.0F-6.0F 0.5C/1F steps
Data format : Fan span * 10

10

0-10V Fan Interval (PI)

10-300 seconds 10 seconds steps (60 seconds default)

11

0-10V Fan direction

0: 0 - 10V – slow to fast
1: 10 to 0V – slow to fast

12

0-10V Fan minimum value
(minimum fan voltage
when running)

0 -10V
Data format : 0-10V Fan minimum value * 10

13

0-10V Fan Maximum value
(Maximum fan voltage
when running)

0 -10V
Data format : 0-10V Fan minimum value * 10

14

Heat span

0.5C-3.0C/1.0F-6.0F 0.5C/1F steps
Data format : Fan span * 10

15

0-10V Heat interval (PI)

10-300 seconds 10 seconds steps (60 seconds default)
16

0-10V Heat direction

0: 10V is 100% open (forward acting)
1: 0V is 100% open n(reverse acting)

Page 15

17

0-10V Heat minimum
Voltage

0 -10V
Data format : 0-10V Heat minimum value * 10

18

Cool span

0.5C-3.0C/1.0F-6.0F 0.5C/1F steps
Data format : Fan span * 10

19

0-10V Cool interval (PI)

10-300 seconds 10 seconds steps (60 seconds default)

20

0-10V Cool direction

0: 10V is 100% open (forward acting)
1: 0V is 100% open n(reverse acting)

21

0-10V Cool minimum
Voltage

0 -10V
Data format : 0-10V Cool minimum value * 10

22

Auto Off Timer

0: No auto off timer
1-10hours 0.5 hours steps
Data format : hour * 10

23

Un-occupied heat
Set point

0: OFF
5C-30C/41F-86F 0.5C/1F steps

24

Un-occupied cool
Set point

0: OFF
5C-30C/41F-86F 0.5C/1F steps

25

Un –Occupied fan mode

Fan 3 Speed mode
1: Low (Auto) (default)
2: Med (Auto)
3: High (Auto)
4: Low (ON)
5: Med (ON)
6: High (ON)

26

Backlight

0: On with button press Only
1: Always On high
2: Low when standby / high when active (Default)

27

TT sensor (SI & Com)

0: Remote – Use this sensor in place of the fitted sensor.
1: Average – Use both remote and fitted sensor and control
to the average temperature of both sensors.
2: Data – Sensor value used for Modbus only.
3 : Duct – Used for 2 pipe mode.

28

Temperature Calibration

+/- 10 deg (C or F)
Adjust to show correct room temp.

29

Digital Input

0: Force Room to Unoccupied Mode
1: Chime Door Bell

30

Digital Input Logic

0: Normally Open
1: Normally Closed

31

Window Input Logic

0: Normally Open
1: Normally closed

32

Window Input Delay

0 - 300 seconds 30 seconds steps (30 seconds default)

33

Door Input Logic

0: Off (default)
1: Normally open
2: Normally close

34

Door Input Delay

0 - 300 seconds 30 seconds steps (30 seconds default)

35

PIR Input Delay

0: Off (default)
1 - 15minutes 1 minute steps

36

Reset Fan

0: Off 1: On
(resets indoor fan to auto every time mode is set to off)

37

Belimo Mode

0: Off 1: On

38

Modbus Address

1-255

Page 16

39

Baud rate

1: 4800bps 2: 9600bps 3:19200bps

40

Factory Reset

0: NO
1:Yes (Exit to initiate)

Modbus Data – Addendum 1

The SMT-131 has integrated Modbus RTU communications. Using a Modbus master controller
such as the Smart Temp 770-HMI many of the SMT-131 thermostat features can be centrally
controlled and monitored.

Modbus is a simple protocol that is extremely popular due to its robustness and simple
implementation. It is also a “forgiving” protocol and will tolerate many installation errors. This
being stated however, correct wiring practices should be used to achieve maximum reliability. See
page 10 for details on wiring Modbus networks.

The SMT-131 Modbus data is within the “40XXX” range, this being holding registers. Depending
on your choice of Modbus Master you may need to enter the address using the full address - such

as “40012” or by selecting “Holding Registers” and entering the address simply as “12”.
These modbus registers are shown as Base “1” (PLC addressing) format. Depending on your

modbus master addressing format you may need to subtract 1 from these values to convert to
base “0” (protocol addressing) format.

Note - The Modbus data layout may seem unorganised in this document, for example 0-10v for
heat and cool is at register 40040 & 40041 while the 0-10V output for the fan is at register 40068.
The reason for this is that the SMT-131 version II has been made 100% backwards compatible
with the SMT-131 version 1. All the functions added to version 2 of the SMT-131 have their
Modbus registers at the end of the version 1 SMT-131 Modbus list.

Data Format

Protocol Modbus RTU
Byte Format 1 Start Bit, 8 Data Bits, 1 Stop Bit, No Parity
Address 1 to 255
Baud 4800 / 9600 / 19200 BPS

Holding
Register

Type

Value

Comments

40001

Read Only

Device ID

Always Returns “131”
Use As A Sentinel Point

40002

Read Only

Firmware Version

Divide By 100 (e.g. Version 2.36 = 236)

40003

Read Only

DIP Switch State

Binary Count
Sw 1 = 1, Sw2 = 2, Sw3 = 4, Sw 4 = 8 etc

40004

Read / Write

Occupancy Status

0 = Room is Unoccupied
1 = Room is Occupied
Note - Modbus can write “0” holding the

Page 17

room unoccupied regardless of the occupancy
input.
Modbus cannot override the occupancy input
and hold the SMT-131 in occupied mode.

40005

Read Only

Bell Status

0 = Bell Is Silent
1 = Bell Is Chiming

40006

Read / Write

Door Station Status

0 = Normal - No Activity

1 = “Make Up Room” Active
2 = “Do Not Disturb” Active

40007

Read / Write

HVAC Status

0 = Air Conditioning Off (1 or 3 Fan Speed)
1 = Low Speed Ventilation ( 1 or 3 Fan Speed)
2 = Med Speed Ventilation (3 Fan Speed Only)
3 = High Speed Ventilation (3 Fan Speed only)
4 = Air Conditioning ON (1 or 3 Fan Speed)

40008

Read / Write

Fan Status

3 Fan Speed Mode

0 = Low (Fan Auto)
1 = Med ( Fan Auto)
2= High (Fan Auto)
3 = Auto Fan Speed (Fan Auto)
4 = Low (Fan On)
5 = Med (Fan On)
6 = High (Fan On)
7 = Auto Fan Speed (Fan On)

1 Fan Speed Mode

0 = Fan Auto
4 = Fan On

40009

Read / Write

User Set Point

Deg C = 0.5°C Steps
Deg F = 1°F Steps
Value / 10 ( e.g. 23.5°C = 235)

40010

Read / Write

Contact Reception
Notification

0 = Off
1 = Show Contact Reception on LCD
SMT-131 LCD will flash “Contact Reception”
on LCD and sound chime. User may accept
alert by touching any button on SMT-131

40011

Read Only

Room Temperature

Value / 10 (e.g. 21.7c = 217)

40012

Read / Write

Temperature
Display

0 = Show Room and Set Temperature
1 = Show Set Temperature Only

40013

Read / Write

Native C/F Display

0 = Deg C format
1 = Deg F format

40014

Read / Write

User Set Point High
Limit

5°C to 30°C Range (41°F-86°F) in 1°C/F Steps
1:1

40015

Read / Write

User Set Point Low
Limit

5°C to 30°C Range (41°f-86°F) in 1°C/F Steps
1:1

40016

Read / Write

Dead Band

0.5°C to 5.0°C in 0.5°C Steps

1.0°F to 10.0°F in 1°F Steps
Value / 10 (e.g. 1.5°C Dead Band = 15)

40017

Read / Write

Relay Span

0.5°C to 3.0°C in 0.5°C Steps
1°F to 10°F in 1°F Steps
Value / 10 (e.g. 1.0°C Span = 10)

Version 3 code – Inactive. Will return valid
Modbus data but function internally disabled

Page 18

40018

Read / Write

Fan Purge Period

0 = Off
1 = Fan Purge - 1 Min
2 = Fan Purge - 3 Min
3 = Fan Purge - 5 Min
4 = Fan Purge - 10 Min
5 = Heat Only Fan Purge - 1 Min
6 = Heat Only Fan Purge - 3 Min
7 = Heat Only Fan Purge - 5 Min
8 = Heat Only Fan Purge - 10 Min
9 = Cool Only Fan Purge - 1 Min
10 = Cool Only Fan Purge - 3 Min
11 = Cool Only Fan Purge - 5 Min
12 = Cool Only Fan Purge - 10 Min

40019

Read / Write

0-10V Heat Span

0.5°C to 3°C in 0.5°C Steps
1°F to 6°F in 1°F Steps
Value / 10 (e.g. Heat Span of 1°C= 10)

40020

Read / Write

0-10V Cool Span

0.5°C to 3°C in 0.5°C Steps
1°F to 6°F in 1°F Steps
Value / 10 (e.g. Cool Span of 1°C = 10)

40021

Read / Write

Auto Off Timer

0 = 0ff
1 to 10 Hours. (0.5 hour steps)
Value / 10 (e.g. 3 Hour Auto Off Timer = 30)

40022

Read /Write

Unoccupied Heat
Set Point

0 = Off
5°C to 30°C in 0.5°C Steps
41°F to 86°F in 1°F Steps
Value / 10 ( e.g. 17°C Unoccupied Heat = 170)

40023

Read / write

Unoccupied Cool
Set Point

0 = Off
5°C to 30°C in 0.5°C Steps
41°F to 86°F in 1°F Steps
Value / 10 ( e.g. 28.5°C Unoccupied Cool =

285)

Page 19

40024

Read / Write

Unoccupied Fan
Mode

3 Fan Speed Mode
1 = Low (Fan Auto)
2 = Med ( Fan Auto)
3 = High (Fan Auto)
4 = Low (Fan On)
5 = Med (Fan On)
6 = High (Fan On)
1 Fan Speed Mode
0 = Fan Auto
4 = Fan On

40025

Read / Write

Backlight

0 = On With Button Press
1 = Always On (High)
2 = Always On Low - High With Button Press

40026

Read / Write

Remote “SI & Com
0-V Temperature
Input Function

0 = Replace On Board Sensor With Remote
1 = Average Onboard Sensor With Remote
2 = Modbus Use Only (e.g. Coil Temp
Monitor)
3: 2 pipe monitor

40027

Read / Write

Digital Input
Function

0 = Occupancy Initiate
1 = Chime Door Bell

40028

Read / Write

Reset Fan Mode

0 = Leave Fan Mode Unchanged
1 = Reset Fan To Auto At Switch Off

40029

Read / Write

Belimo Mode

0 = Standard 0-10V Valve Logic
1 = Belimo 6V = Off 3 Way Valve Logic

40030

Read / Write

Modbus Address

1 to 255

40031

Read / Write

Baud Rate

1 = 4.8Kbs
2 = 9.6kbs
3 = 19.2Kbs

40032

Read Only

Digital Input Status

0 = Open
1 = Closed

40033

Read Only

Internal Sensor
Value

Value / 10 (e.g. 23.3°C = 233)

40034

Read Only

Remote Sensor
Value

Value / 10 (e.g. 21.8°C = 218)

40035

Read Only

W relay status

0 = Off
1 = Energised

40036

Read Only

Y Relay Status

0 = Off
1 = Energised

40037

Read Only

High Fan Relay
Status

0 = Off
1 = Energised

40038

Read Only

Medium Fan Relay
Status

0 = Off
1 = Energised

40039

Read Only

Low Fan Relay
Status

0 = Off
1 = Energised

40040

Read Only

0-10V Heat Value

Value / 100 (e.g. 7.3V = 730)

40041

Read Only

0-10V Cool Value

Value / 100 (e.g. 2.1V = 210)

40042

Read Only

Permitted Modes
(ver 2.1+ only)

0 = Auto (Heating and cooling called)
1 = Heat Only Mode
2 = Cool Only Mode

Page 20

Values below only apply to version 2 hardware only, Firmware version 3+

40043

Read / Write

2 pipe mode
changeover

0 = Heat
1 = Cool

40044

Read / Write

Thermostat
Displaying

0 = Deg C
1 = Deg F

40045

Read / Write

Buttons shown on
display

0: Both mode and fan buttons show (default)
1: Show mode but hide fan button
2: Show fan but hide mode button
3: Hide both mode and fan buttons

40046

Read / Write

Permitted Modes

0: Off / Auto
1: Off / Heat / Cool / Auto
2: Off / Heat / Cool
3: Off / Heat
4: Off / Cool

40047

Read / Write

Swap C/F display
shown on display

0: C/F Button hidden
1: C/F button shown

40048

Read / Write

Fan Span for 3
speed relays

0.5C-3.0C/1.0F-6.0F 0.5C/1F steps
Data format : Fan span * 10

40049

Read / Write

0-10 Fan Interval

10-300 seconds in 10 second steps (60
seconds default.

40050

Read / Write

0-10 Fan Direction

0: 10V is 100% open (forward acting)
1: 0V is 100% open (reverse acting)

40051

Read / Write

0-10 Fan Minimum
Voltage.

0-10v (Fan value x 10)

40052

Read / Write

0-10 Heat Interval

10-300 seconds in 10 second steps (60
seconds default.

40053

Read / Write

0-10 Heat Direction

0: 10V is 100% open (forward acting)
1: 0V is 100% open n(reverse acting)

40054

Read / Write

0-10 Heat Minimum
Voltage

0-10v (Heat value x 10)

40055

Read / Write

0-10 Cool Interval

10-300 seconds in 10 second steps (60
seconds default.

40056

Read / Write

0-10 Cool Direction

0: 10V is 100% open (forward acting)
1: 0V is 100% open n(reverse acting)

40057

Read / Write

0-10 Cool Minimum
Voltage

0-10v (Cool value x 10)

40058

Read / Write

Window input logic

0: Normally Open
1: Normally closed

40059

Read / Write

Window input Delay

0-300 seconds in 30 second steps

40060

Read / Write

Door input logic

0: Normally Open
1: Normally closed

40061

Read / Write

Door input Delay

0-300 seconds in 30 second steps

40062

Read / Write

PIR input Delay
(Seek Time)

0:Off
1-15minutes in 1 minute steps

40063
40064

Read / Write

Unit run time log

0-9999.9 hours
Run time x 10

40065

Read Only

Window Input
Status

0:Closed
1:Open

40066

Read Only

Door Input Status

0:Closed
1:Open

Page 21

40067

Read Only

PIR Status

0:No Movement detected
1:Movement detected

40068

Read Only

0-10V Fan Value

Value / 100 (e.g. 2.1V = 210)

40069

Read Only

0-10V Fan Max
Value

0-10v (@*10)

40070

Read / Write

Digital Input logic

0:Normally Open
1:Normally Closed

Specifications

Input Voltage 24VAC 50/60 Htz +/- 15%
Operating Temperature 0°C to 50°C (32°F to 122°F)
Operating RH 0-95% (Non Condensing)
Storage Temperature 0°Cto 65°C (32°F to 150°F)
Size 113 x 103 x 25mm.
Display Size 69.5 x 46.3mm.
Backlight White LED (Other Colours Available Upon Request)
Display Type STN Touch Panel
Relay Rating 30V @ 1Amp Max
0-10V Output Load 10mA Max
Control Range 5°C to 30°C (41°F to 86°F)
Memory Type Non Volatile - Settings Do Not Require Battery Backup
Communications Modbus RTU 4 .8K / 9.6K / 19.2 K
1 Stop Bit, 8 Data Bits, 1 Start Bit. No Parity.
Plastic ABS / Poly Blend – UV Stabilised and Fire Rated
Warranty 3 Year RTB

Great care has been taken in the preparation of this manual. Smart Temp Australia P/L takes no

responsibility for errors or omissions contained in this document. It is the responsibility of the

user to ensure this controller or equipment connected to it, is operating to their respective

specifications and in a safe manner.

Due to ongoing product improvement Smart Temp Australia P/L reserves the right to change the

specifications of the SMT-131 thermostat (or its components) without notice.

All rights reserved. © Smart Temp Australia P/L 2011

Intellectual rights apply.