S-therm Yukon

Use cases

• Monitor water inlet and outlet temperatures on a live dashboard to verify heat pump efficiency.
• Create alerts when DHW tank temperature drops below a minimum threshold for more than 15 minutes.
• Remotely adjust Zone 1 and Zone 2 heating setpoints based on occupancy schedules or weather forecasts.
• Track compressor operation hours to plan preventive maintenance before failures occur.
• Switch the heat pump on or off remotely during commissioning or seasonal shutdown without a site visit.
• Log outdoor unit voltage and current to detect electrical supply issues early.

Installation

1. 1Connect the ModbusCloud gateway (MCG or MLP series) to the Sinclair S-therm Yukon RS-485 terminals using a twisted-pair cable with correct A/B polarity.
2. 2On the heat pump controller, enable Modbus RTU communication and set the baud rate to 9600 with the appropriate slave address.
3. 3Verify that the RS-485 bus is terminated correctly, especially if the gateway and heat pump are the only two devices on the bus or at opposite ends of a longer chain.
4. 4In the ModbusCloud portal, add a new device and import the Sinclair S-therm Yukon template, then assign the matching Modbus slave address.
5. 5Power on the gateway and confirm that live readings (water temperatures, pressures, compressor status) appear on the dashboard.
6. 6Test write access by toggling the on/off register and verifying the heat pump responds.

Things to watch for

01

The gateway cannot communicate with the heat pump. What should I check first?

Verify that the RS-485 A and B wires are not swapped. Also confirm that the baud rate on both the heat pump and the gateway is set to 9600, and that the slave address in the template matches the address configured on the heat pump.

02

Temperature values appear incorrect or unrealistically high. Why?

This is usually a scaling issue. Ensure you are using the template as provided, because it already applies the correct scaling factors. If you have edited register definitions, double-check that the data type and decimal point settings match the Sinclair Modbus documentation.

03

Can I connect multiple Sinclair heat pumps on the same RS-485 bus?

Yes, as long as each heat pump has a unique Modbus slave address. Add a separate device in the ModbusCloud portal for each unit, import the same template, and set the corresponding slave address.

04

Do I need a specific firmware version on the heat pump for Modbus to work?

Modbus RTU support is available on all listed compatible models. If communication does not start, consult the Sinclair installation manual for your model to confirm that the Modbus option is enabled in the service menu.

Registers (40)

33 read / 7 write

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