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Multiple simultaneous connections to Samsung R290 heat pump via Modbus

Air Source Heat Pumps (ASHPs)

Last Post by Broadsman 3 days ago

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Angus

(@angus)

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27 kWhs

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Topic starter 27/03/2025 1:30 am

I plan to get a Samsung R290 5kW heat pump.

Homely has been recommended and so will connect to the heat pump via the MIM-B19N Modbus interface.

I want to be able to monitor the heat pump's internal data directly, and possibly add to it by connecting my own flow and return temperature sensors as I have read that Samsung's values are sufficiently inaccurate to skew COP calculations. (But, make use of its flow data - which is said to be accurate - and which avoid installing an external flow meter.)

Does anyone know if the MIM-B19N Modbus interface will support multiple connections? And, if so, would this just be a matter of adding a second pair of wires to its terminals from, for example, a Modbus RS485 to USB Adaptor?

Thanks

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JamesPa

(@jamespa)

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27/03/2025 4:14 pm

My understanding of modbus is that its a master slave system. One unit must be designated the master, others are slaves. i dont know how you do this. You can definitely connect multiple slaves, doubtless up to some max number which I dont know.

Thats probably not definitive enough for which I apologise. Maybe someone will come along with a definitive answer.

This post was modified 4 days ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Arundalep

(@arundalep)

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27/03/2025 4:27 pm

Technically, no, Modbus cannot have multiple connections, but you can decode the Modbus data using an RS-485 interface and suitable software (a Modbus sniffer). The Homely becomes the Modbus master (requesting the data from the Samsung); only one master is allowed.

That being said, I have tried multiple connections (Homely and Home Assistant), and it does work most of the time, but I would not recommend it. It can be flaky and very slow.

It's far easier to use a simple off-the-shelf interface (M5 Stack Atom + RS485 base ATOMIC RS485 Base | The Pi Hut) and wire directly to the F1/F2 terminals. You will get much more data and controls available using this method (using the Samsung NASA protocol). There are multiple software options for this method on GitHub. I use ESP-Home and Home Assistant which works great.

1970’s 3 bed detached house in West Sussex. Mains gas disconnected September 2023.
Samsung HTQ 8kW heat pump using mostly existing radiators. House is warm 24/7 (normally between 20.3-20.6 C but currently with a newborn its 21-21.2 C).
Sunamp for hot water storage.
Solaredge 6kWp PV and 10kWh battery
Vehicle 2 Grid charger (used with a Leaf)
Wallbox EV charger (installed for Octopus Intelligent).
Home Assistant used for HEMS with lots of custom ESP devices to allow integration.

Insulation upgrades:
EPS cavity wall insulation.
Improved loft insulation (renewed and 300mm where possible).

🤩

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Broadsman

(@broadsman)

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28/03/2025 9:20 am

@arundalep Thank you that's useful info. I have modbus with Planet Devices which gives me plenty of data but no control. I have just fitted the long awaited wifi kit and linked to SmartThings and am about to try Havenwise. Should that not be successful I would try Homely via the modbus

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