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

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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.

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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 0-
10V 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

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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 SMT-
131 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

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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 SMT-
131, 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 SMT-
131 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.

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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.

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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)

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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

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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