What would be the easiest DIY multi-zone setup?

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What would be the easiest DIY multi-zone setup?

Post by Basso12 »

Hello,
I would like to realise a DIY multi-zone heating system with the combination of several OT thermostats, electric valves and a Raspberry Pi running Domoticz.

Basically I want to open a valve when a zone requests heat. And start the boiler when one or more zones request heat. The opening of valves I plan to do with several relays connected to the GPIO of the raspi, but im a bit stuck with detecting heat requests by more than one zone.

I bought one OTGW from the NODO-shop, but what would be the best option to listen to more than one thermostat?

And if possible, how could I still make use of modulation abilities of my Remeha Avanta boiler?
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Re: What would be the easiest DIY multi-zone setup?

Post by Akatar »

There is standard 1 opentherm thermostat connected to the boiler and/or otg
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Re: What would be the easiest DIY multi-zone setup?

Post by Basso12 »

Akatar wrote:There is standard 1 opentherm thermostat connected to the boiler and/or otg
I know I can't easily use the modulation capacities of the protocol with multiple thermostats. But perhaps i still can use the protocol to read roomtemp and setpoint of several thermostats and override (reset) their set-point when my DIY time/presence based algorithm takes over control.

I already changed the heating system from high temp radiators to low temp floor heating with a maximum water temp of max 35°. This low temp and the "slowness" makes modulation probably less beneficial. So I guess I'm okay with a smart on/off system.

I just stuck with communicating with multiple thermostats from the raspi.
perhaps I need something like this? https://diyless.com/product/slave-opentherm-shield or this https://www.tindie.com/products/thehogn ... emoslolin/
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

Hi,
To read opentherm data from opentherm compatible thermostats you need a opentherm slave.
There are a few solutions for this, all based on the original design from Schelte Bron.

Mine (on that tindie link) is a simple slave module as a shield on top of a Wemos/Lolin ESP8266 board and it works just like al other opentherm slave boards. Only difference to that one on diyless.com is that on my version the 24v boost is from the 5v rail and on the diyless it is from the 3.3v rail (the GPIO is still 3.3v though). As most Wemos boards are powered from USB (5v) this is better as it saves the step from 5v to 3.3v back to 24v. But for the user it is transparant, they work the same.

There are a few arduino libraries but they are more focused to work as a master. Slave libraries are a bit buggy. I'm still working on my implementation.

But you can use that same slave module on top of a raspberry PI also (although not pin layout compatible ofcourse).
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Re: What would be the easiest DIY multi-zone setup?

Post by Basso12 »

TheHogNL wrote:Hi,
To read opentherm data from opentherm compatible thermostats you need a opentherm slave.
There are a few solutions for this, all based on the original design from Schelte Bron.

Mine (on that tindie link) is a simple slave module as a shield on top of a Wemos/Lolin ESP8266 board and it works just like al other opentherm slave boards. Only difference to that one on diyless.com is that on my version the 24v boost is from the 5v rail and on the diyless it is from the 3.3v rail (the GPIO is still 3.3v though). As most Wemos boards are powered from USB (5v) this is better as it saves the step from 5v to 3.3v back to 24v. But for the user it is transparant, they work the same.

There are a few arduino libraries but they are more focused to work as a master. Slave libraries are a bit buggy. I'm still working on my implementation.

But you can use that same slave module on top of a raspberry PI also (although not pin layout compatible ofcourse).
Thank you for your reply, I have a couple of additional questions if thats okay?

1. Can your slave board also be used to override/reset the thermostats setpoint as well?
2. Your board uses 2 GPIO pins if I see correct. Are these actual general purpose gpio's? or do the require a special function function like L2c, Uart, or something like that?
3. Could I connect 4 of these boards to a raspi as long as I have enough GPIO's?
4. Could you provide a link to a slave library?
5. Would a 15m cable between such board and a thermostat be a problem?
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

1. It is only a slave module. So it acts like a boiler itself. The thermostat is the master and communicaties its setpoint. But (and read here uploaded/Ard%20M/Opentherm%20Protocol%20v2-2.pdf at 5.3.8.3) opentherm provides an override settpoint option. Depends on the thermostat if it is supported. However, if you mean that you want to override the communication to the real boiler, you need a master module also. Or find another way start the boiler.
2. Those are generale GPIO's, designed for 3.3v logic. Your controller can use this as it likes from the library. Some libraries use hardware uart, others software uarts.
3. Yes.
4. On the tindie page I link to two libraries.
5. If that works between a boiler and your thermostat it works for this also. Again, this module is the 'boiler part' of opentherm so you will find the same logic in a standard opentherm compatible boiler also.

So yes, you can use 4 modules to receive the opentherm data from 4 different thermostats and then based on that information do anything you like.
I could also make a dedicated board for 4 opentherm slave inputs for you. And if you like a seperate 1 master output. It is just copy pasting the schematics. Raspi is 5v logic, so I would probably change it to 5v logic also.
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

Hi,
Thinking about this and your original post where you only ask for detecting heat requests from multiple zones.
You could just easily use the on/off signal of the thermostat (instead of opentherm). The on/off on a thermostat function like shorting a circuit or not. So you could use a GPIO to detect that (just like a switch).

Only if you would like to know more about the thermostat (like modulation, setpoint, roomtemp etc) you would need to have those slave opentherm modules per zone/thermostat.
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Re: What would be the easiest DIY multi-zone setup?

Post by Basso12 »

I appreciate your help!

I have a programming background, but I'm a newbie when it comes to connecting hardware.

Can I use each slave connection the same way as the OTGW from the nodo-shop that I have? I like the way I can create a "Device" of the roomtemp and room setpoint. Also override setpoint seems to be built in this Domoticz device because that when I change the value in Domoticz the setpoint on the thermostat actually changes.

also, I'm still a bit confused about the pins because I'm thinking when a library uses UART the board should be connected to a UART pin, or not?

The idea for a combined board sounds great! For now I'm thinking of 6 zones. As mentioned I already have a OTGW from the nodo-shop which I could use for one slave and the master. So the combined board should have 5 slave connections.
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

Hi,
UART isn't used. It is based on normal GPIO's.
Some libraries use interrupt based GPIO handeling, others use polling based.
If you use the interrupt based, you must have enough interrupt capable GPIO's.

The OTGW device from the nodo-shop is somewhat different. The OTGW code is there running on the microcontroller on the board itself. The extra wifi option with esp8266 is only to control that microcontroller.
However, this wemos shield requires you to 'talk' opentherm yourself (using the libraries). But yes, you can then use the input from the thermostat (and output to the thermostat) anyway you like.

Depening what you want I can create a design for you. Do you want it for a Pi, a ESP8266 (which doesn't have enough GPIO's for your use case), a ESP32 or some other arduino microcontroller?
Or just get 5 shields and 5 Wemos/Lolin ESP8266 modules :)
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Re: What would be the easiest DIY multi-zone setup?

Post by hvxl »

TheHogNL wrote:Raspi is 5v logic
Nope. The Raspberry Pi GPIO pins work with 3.3V logic levels and are not 5V tolerant. If you apply 5V to a GPIO pin you risk permanently damaging it.
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

hvxl wrote:
TheHogNL wrote:Raspi is 5v logic
Nope. The Raspberry Pi GPIO pins work with 3.3V logic levels and are not 5V tolerant. If you apply 5V to a GPIO pin you risk permanently damaging it.
Correct. I was mixing up with the Arduino Uno board :). RaspPi is indeed 3.3v.
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Re: What would be the easiest DIY multi-zone setup?

Post by Basso12 »

TheHogNL wrote:Hi,
The OTGW device from the nodo-shop is somewhat different. The OTGW code is there running on the microcontroller on the board itself. The extra wifi option with esp8266 is only to control that microcontroller.
However, this wemos shield requires you to 'talk' opentherm yourself (using the libraries). But yes, you can then use the input from the thermostat (and output to the thermostat) anyway you like.

Depening what you want I can create a design for you. Do you want it for a Pi, a ESP8266 (which doesn't have enough GPIO's for your use case), a ESP32 or some other arduino microcontroller?
Or just get 5 shields and 5 Wemos/Lolin ESP8266 modules :)
3 heating zones will be 2 levels up and I already planned to use a separate arduino on that 2nd house level (connected to the raspi by a 10m usb cable). So I would probably go for a combined 2 slave board for the raspi and later 3 for an arduino nano (ATMEGA328P).

So you say with your shields I will be able to represent each thermostat's room-temp and set-point as an (over-ridable) "device" in Domoticz, Thats would be great! with this I can make the multi-zone set up working. What "hardware type" in Domoticz would work with your slave board?

Please email my for the details on combined 2 slave boards for the raspi.
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

Basso12 wrote:
TheHogNL wrote:Hi,
The OTGW device from the nodo-shop is somewhat different. The OTGW code is there running on the microcontroller on the board itself. The extra wifi option with esp8266 is only to control that microcontroller.
However, this wemos shield requires you to 'talk' opentherm yourself (using the libraries). But yes, you can then use the input from the thermostat (and output to the thermostat) anyway you like.

Depening what you want I can create a design for you. Do you want it for a Pi, a ESP8266 (which doesn't have enough GPIO's for your use case), a ESP32 or some other arduino microcontroller?
Or just get 5 shields and 5 Wemos/Lolin ESP8266 modules :)
3 heating zones will be 2 levels up and I already planned to use a separate arduino on that 2nd house level (connected to the raspi by a 10m usb cable). So I would probably go for a combined 2 slave board for the raspi and later 3 for an arduino nano (ATMEGA328P).

So you say with your shields I will be able to represent each thermostat's room-temp and set-point as an (over-ridable) "device" in Domoticz, Thats would be great! with this I can make the multi-zone set up working. What "hardware type" in Domoticz would work with your slave board?

Please email my for the details on combined 2 slave boards for the raspi.
Hi I just sent you the email. Still wondering if you are aware that this is not a plug-and-play solution. It is only the hardware, you need to code the opentherm logic yourself (or expand on a available open source library).
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Re: What would be the easiest DIY multi-zone setup?

Post by TheHogNL »

I now also have the opentherm master shield available on my Tindie store (https://www.tindie.com/products/thehogn ... emoslolin/).

Next challange for me would be design a multi-slave/single-master and a multi-slave/multi-master pcb with integrated ESP32. If there is anyone interested in such a PCB, let me know.
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Re: What would be the easiest DIY multi-zone setup?

Post by AndrewFG »

I know it is not the essence of your question, but you could perhaps look at the Tado system https://www.tado.com/

They have a wired smart thermostat which acts as the 'master' controller, and which connects via the OpenTherm bus to command your boiler. And additionally they have thermostatic radiator valves (TRVs) that you can use in each individual room, and which talk to the master thermostat, so that when any room TRV is calling for heat, the TRV tells the master, and the master tells the boiler to produce heat.

You could also connect an OTGW on the OpenThem bus between the Tado master thermostat and the boiler slave, in order to monitor or override what is going on.
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