Simple (and cheap) smart thermostat solution for HVAC fan coils

Hardware
1

Hi there

I want to replace some mechanical Honeywell xe70 series t6371 which i’m using for HVAC system with something smart allowing me to lock temperature and schedule on/off time.

It would be amazing if configurable via Home Assistant (via mqtt ?) as i already use shellies devices to mange some of my building automations (boilers, pumps and temperature).

I also have some Aermec WMT10 Aermec PXA I and it would be amazing if i can work on them too. I think that the only problematic step is that these are not actively powered by 220v. I’m in Italy.

Here’s some schematics:

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I also have some Aermec FCW PFW2
fcw_2016_l-de-en-es-fr-it.pdf

I have some other fan coils but for them as they are “more analog” i think i will proceed just by shutting down power when temperature reaches limit.

2

So use few Shellies and some temperature sensor to replace the thermostat.

3

Mc6 . I have 4 now running without issues. MQTT or modbus tcp. Native integration

4

Like this way i can just shut the power down or turn it on?

5

There are three fan speeds as well. Do you have both caldo e freddo?

6

Yaeh i have fan speed and heat/cold controls. I just dont understand how to use a shelly for all these functions.

7

Do you have any link for that model?

8

You need few Shellies.
Another option could be Esphome dev board and 4ch relay module.

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9

Yeah as multiple shelly won’t be cheap as i have several of these thermostat.
As they are “stupid” fancoils i think i can just turn the power off on temperature so i just need a single shelly and leave the thermostat mounted to control the rest of the functions.

10

I bought directly from them paying via PayPal.
The device arrived without issues. I bought one piece spare as the warranty management from china may be problematic…

Great post sales support, they fixed an issue I found via OTA upgrade after only 2 days

1 Like
11

Good option as well.
I personally would go with Esphome approach though.
Yet to see one good smart thermostat…

1 Like
12

What the wiring should be like? The problem is that a 4ch relay is not really small and i should find a way to fit everything.

13

You could put the relays next to fancoil, where thermostat wires arrive.
For better support post some photos/info of your actual setup.

14

Still haven’t found a cheap and scalable solution for these thermostats.
An ESP would require a power adapter which is no really a easy setup for a wall mounted thermostat.
Do you think it enough to place a shelly here and use it as a normal switch?

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Then i will probably also need an addon for the temeprature sensor. And i don’t know if i have enough room for all of that. I could use a shelly blu H&T to avoid space problems where the cables are but it would add the battery hassle.
I’m also investigating a possible alternative for some rooms where i don’t have a wifi connection.

To partially address this (in some rooms where i can) i’m now controlling via a virtual thermostat the water pumps so they stop once the desired temperature is reached.
I’m controlling them via bacnet/IP as they are on an eagle honeywell controller (which i cannot expand or edit as it requires an expensive licence).