User Manual

Page 22
The 3 x 0-10V (40040 (Heat), 40041 (Cool) & 40068 (Fan)), outputs can be controlled by Modbus
at any time without restriction.
To permit Modbus to control the output first enter 1000 in the register you wish to override, it is
then unlocked from SMT-131 control and you are then permitted to enter the value you wish
the selected output to be; such as 0=relay OFF and 1 1=relay ON or 63 should you wish the 0-10v
to output 6.3v.
To return the output to SMT-131 control simply enter 1001 into the register.
Please Note - Writing to the relays or 0-10V output via Modbus bypasses the SMT-131 internal
memory protection logic. Changing these values regularly via Modbus may reduce the
thermostats memory life to only a few years. Using this function will void the SMT-131
warranty for the memory chip within the thermostat.
40035
Read Only
Read Write
(3.09+)
W relay status
0 = Off (under thermostat control)
1 = Energised (under thermostat control)
1000 = Held OFF by Modbus
1001 = Held ON by Modbus
40036
Read Only
Read Write
(3.09+)
Y Relay Status
0 = Off (under thermostat control)
1 = Energised (under thermostat control)
1000 = Held OFF by Modbus
1001 = Held ON by Modbus
40037
Read Only
Read Write
(3.09+)
High Fan Relay
Status
0 = Off (under thermostat control)
1 = Energised (under thermostat control)
1000 = Held OFF by Modbus
1001 = Held ON by Modbus
40038
Read Only
Read Write
(3.09+)
Medium Fan Relay
Status
0 = Off (under thermostat control)
1 = Energised (under thermostat control)
1000 = Held OFF by Modbus
1001 = Held ON by Modbus
40039
Read Only
Read Write
(3.09+)
Low Fan Relay
Status
0 = Off (under thermostat control)
1 = Energised (under thermostat control)
1000 = Held OFF by Modbus
1001 = Held ON by Modbus
40040
Read Only
Read Write
(3.09+)
0-10V Heat Value
Value / 10 (e.g. 7.3V = 73)
(To write add 10 e.g. - to write 7.3v send
1073
40041
Read Only
Read Write
(3.09+)
0-10V Cool Value
Value / 10 (e.g. 2.1V = 21)
(To write add 10 e.g. - to write2.1v send 1021
40042
Read Only
Permitted Modes
(ver 2.1+ only)
0 = Auto (Heating and cooling called)
1 = Heat Only Mode
2 = Cool Only Mode
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