S-therm Ontario
Monitors and controls Sinclair S-therm Ontario heat pumps via Modbus RTU
This template integrates Sinclair S-therm Ontario heat pumps via Modbus RTU. It reads operating status, temperatures, and thermostat data, and allows control of on/off, operating mode, temperature setpoints, e-heater, and error reset.
- Protocol
- Modbus RTU
- Connection
- RS485, 9600 baud
- Registers
- 30, read and write
- Brand
- Sinclair
- Key readings
- Unit status · T-outdoor · T-water in/out PE · T-tank control · T-remote room · Thermostat
- Available commands
- On/Off and Mode · Temperature setpoints (cool/heat) · E-Heater control · Error reset
- Compatible models
- SMH-40IRB · SMH-60IRB · SMH-80IRB · SMH-100IRB · SMH-100IRB2 · SMH-100IRB2-3 · SMH-120IRB2 · SMH-120IRB-3 · SMH-140IRB · SMH-140IRB-3 · SMH-160IRB2 · SMH-160IRB-3 · SMH-40IRBC · SMH-60IRBC · SMH-80IRBC · SMH-100IRBC2 · SMH-120IRBC2 · SMH-140IRBC2 · SMH-160IRBC2 · SMH-80IRBC2-3 · SMH-100IRBC2-3 · SMH-120IRBC2-3 · SMH-140IRBC2-3 · SMH-160IRBC2-3 · SMH5-40B · SMH5-60B · SMH5-80B · SMH5-100B · SMH5-120B · SMH5-140B · SMH5-160B · SMH5-80B-3 · SMH5-100B-3 · SMH5-120B-3 · SMH5-140B-3 · SMH5-160B-3 · SMH5-40BC · SMH5-60BC · SMH5-80BC · SMH5-100BC · SMH5-120BC · SMH5-140BC · SMH5-160BC · SMH5-80BC-3 · SMH5-100BC-3 · SMH5-120BC-3 · SMH5-140BC-3 · SMH5-160BC-3
- Last updated
Registers (30)
30 read, 21 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Mode | Read and write | ||||
| Optional E-Heater | Read and write | ||||
| WOT-Cool | ℃ | Read and write | |||
| WOT-Heat | ℃ | Read and write | |||
| RT-Cool | ℃ | Read and write | |||
| RT-Heat | ℃ | Read and write | |||
| T-water tank | ℃ | Read and write | |||
| T-Eheater | ℃ | Read and write | |||
| T-Other switch on | ℃ | Read and write | |||
| Upper AT-Heat | ℃ | Read and write | |||
| Lower AT-Heat | ℃ | Read and write | |||
| Upper RT-Heat | ℃ | Read and write | |||
| Lower RT-Heat | ℃ | Read and write | |||
| Upper WT-Heat | ℃ | Read and write | |||
| Lower WT-Heat | ℃ | Read and write | |||
| △T-Cool | ℃ | Read and write | |||
| △T-Heat | ℃ | Read and write | |||
| △T-hot water | ℃ | Read and write | |||
| △T-Room temp | ℃ | Read and write | |||
| On_Off | Read and write | ||||
| Error reset | Read and write | ||||
| Unit status | Read | ||||
| T-outdoor | ℃ | Read | |||
| T-water out PE | ℃ | Read | |||
| T-optional water sen. | ℃ | Read | |||
| T-water in PE | ℃ | Read | |||
| T-tank ctrl. | ℃ | Read | |||
| T-remote room | ℃ | Read | |||
| Thermostat | Read | ||||
| T-weather depend | ℃ | Read |
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Use cases
- Monitor water inlet and outlet temperatures on a live dashboard to verify heat pump performance remotely.
- Create an alert when outdoor temperature drops below a critical threshold so you can check anti-freeze protection.
- Adjust heating and cooling setpoints remotely from the ModbusCloud platform without an on-site visit.
- Track unit on/off status and operating mode to detect unexpected shutdowns or mode changes.
- Set up automatic error notifications and perform remote error resets to reduce truck rolls.
- Log tank control temperature over time to optimise domestic hot water scheduling for the end customer.
Installation
Connect the Modbus RTU wiring (A, B, GND) from the Sinclair S-therm Ontario heat pump to the RS-485 port on your ModbusCloud Gateway.
Set the Modbus slave address on the heat pump controller and note it for configuration in the ModbusCloud platform.
Ensure the heat pump serial communication is configured to 9600 baud, 8 data bits, 1 stop bit, no parity, matching the template defaults.
Import the Sinclair S-therm Ontario template in the ModbusCloud portal and assign the correct slave address.
Verify communication by checking that unit status and temperature readings appear on the dashboard.
If multiple heat pumps are connected on the same bus, assign unique Modbus addresses to each unit and add a separate template instance per device.
Things to watch for
Why does the outdoor temperature show an incorrect or very high value?
Register 118 for outdoor temperature uses a signed int16 data type. If your setup interprets it as unsigned uint16, negative temperatures will appear as large positive numbers. The template handles this automatically, but verify that no custom override changes the data type.
What baud rate should I set on the heat pump?
The default baud rate for this template is 9600. Make sure the Sinclair heat pump and the Modbus gateway are both set to 9600 baud, 8N1. A mismatch will prevent communication.
Can I control the heat pump and read data at the same time?
Yes. The template defines both read and write registers. Reading status and temperatures happens on a polling cycle, while control commands such as on/off or setpoint changes are sent when you trigger them from the dashboard.
How do I know which model variant I have?
Check the model label on the outdoor unit. The template supports all SMH-IRB, SMH-IRBC, SMH5-B, and SMH5-BC variants from 40 to 160 size classes, including three-phase models ending in -3.
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