Hi there,
sorry for the very newbie questions!
there are some fancoils that I like that are produced by a number of brands such as daikin, riello, innova, baxi, beretta, ariston, paradigma, and probably many more.
For example Riello (cheapest price and reputable brand) has models 11p, 17p and 23p that support an external thermostat which in turn can be connected to a modbus master.
Unfortunately none of these models allow for both (ir) remote control AND wifi . If anyone knows of similar high-wall models with that feature it would solve all my problems, but missing that, I am trying to see how a modbus can be used.

I'd have a few questions:

1. the thermostat connects to the fancoil with the same A-B cables that are used to connect thermostat and modbus master, does this typically mean that the signals are the same on both lines? (ie: if I wanted I could connect the master directly to the fancoil?)
2. is there (typically) a way to use one thermostat to drive 2 fancoils (on - off, temperature), while keeping the possibility to then lower the temperature or fan speed on one of the 2 fancoils separately?
3. ultimately I am trying to connect the modbus to my home assistant or google home, or other home automation system, so I can control remotely the fancoils, while at the same time having a physical hardware that allows me to control them in the home.
   My ideal setting would be: A) 1 thermostat for the whole home + 2 (IR) remote controllers to tweak the individual settings of each fancoil if needed + B) wifi , ethernet, zigbee, modbus or anything else -ideally with an open protocol- to control the fancoils either as one or individually.

sorry if this is a typical case of user who does not read the forums, but I wouldn't even know what to search for. I am quite technical with programming and electronics, but completely new to rs485 and modbus rtu.

Thanks to anyone who may help!!

 

There are thousands of devices that have Modbus serial communications and if Modbus is available (sometimes only as a paid option) then Modbus is mentioned. Devices that do not mention Modbus do not have Modbus implemented. It would possible to implement Modbus but not release details of how Modbus is implemented, and in fact this forum receives occasional requests for vendor Modbus documentation that is not readily available from the vendor.

But consumer devices in the category of these heat exchangers, Modbus is not mentioned and there is very little likelihood that Modbus is even used for the communications from the all mounted CPD 35 remote controller and the fan coil units. It is highly likely that the hardware bus is RS-485, given the warning to heed the polarity of the A/B lines, because RS-485 had polarized A/B driver lines and the ability to run "multidrop" to more than one device linked in series on the communications line. But Modbus is the protocol, the set of rules the communications uses; RS-485 is just the hardware bus. There are thousands of proprietary, vendor-only protocols that run over RS-485, each incompatible with the other. The word ASCII shown one of the printed circuit boards in the vicinity of the comm connector might well indicate a proprietary ASCII comm protocol over RS-485.

One of the Fan coil on-line manuals:
https://all-guidesbox.com/manual/16...-the-technical-service-centre-36.html?page=34

These units are outside my experience so I can't tell you whether any is sold with Modbus slave/server functionality, but it wouldn't surprise me none did given the complexities of Modbus and the recognition by the vendor of the support costs involved with supporting an open protocol, versus using a proprietary protocol that works with their hardware only.

If your home automation software program supports Modbus then you'll have do the leg work to search and find a vendor selling components that are Modbus compatible. Even then the answer to your question like, "Is there (typically) a way to use one thermostat to drive 2 fancoils (on - off, temperature), while keeping the possibility to then lower the temperature or fan speed on one of the 2 fancoils separately?" is: depends on the software implementation and if the feature is not included, does the program allow customized coding and can you do the customized coding to create the feature.

 

Here is a post that may help you learn modbus
https://www.breezecontrols.com/modbus-thermostat.html