Opentherm support

[emilic14]

Hello,

To be fully transparent, I am still not using your amazing project but it is in my todo list (just installed my heat pump this week and I am still setting up things).
But I wanted to know if you are managing opentherm and if so, how, and if not, if it would be of interest...

My use case is simple, I have a Nest device that used to handle my heating (gas) system, its a nice device as well it tell you the outside temp, has a movement detector, can control the temperature of the heater, etc. And I believe that with opentherm it could also control the heating of the water heater...
Anyhow, my idea of usage is to have the nest connected to my device to display information, and if possible to control the heating devices (not the heat pump) of the room where I have it connected.

[edterbak]

Hi @emilic14
Sorry for not responding earlier.

I have no real grasp yet on what I can do with the opentherm signal towards the heatpump.
If I would receive a signal which gives me a percentage of the requested heat/power, how would I process that.

The heatpump works with setpoints. Water temperature in/out vs setpoints.
This is a temperature game.

The only thing I could think of, is mapping the requested setpoint to the requested heat%

Request %	Setpoint C
0	20
10	22
20	24
..	..
90	33
100	35

This would behave then something similar as to the RTC-function.

But the above is but a thought-experiment. I dont know yet.
It starts with a good plan

edit...
Thinking about it more.
I am not sure if a heatpump is very well suited to be operate in such a manner.
A Nest, smart thermostat is something that is learning the heating characteristics of the house.
I think this process works well with a regular gasfired boiler. It has a strong output which is well measurable for the 'smart' analysis of the house. A relative fast response time makes it easier to measure and analyse its influence.

But I am very doubtfull if a heatpump would work in such a scenario.
Low water temperatures out, means little effect as a result. There are many external factors like outside temperature which have a relative high impact on the efficiency and behaviour of the heatpump. Defrosts, stop/start cycles.

The longer I think about it, the more I lean towards the... "dont go there" zone. But.. this is what I can imagine about it, and what I know about it. Which is not a lot.

But maybe I am missing some info on what the NEST is also capable of. Maybe there are settings especially for this situation. :)

[emilic14]

Thank you for your answer and thoughts.

Currently I am not really using the Opentherm part as it is not really working with the Nest device that I have, I dont know why, but I have open an issue on the correct git.

That said, to my understanding the Nest could also handle DHW with opentherm, but I dont see why I would change the wanted value often for the DHW...

At the end I mostly use my Nest as a nice display that can provide a temperature measure at the middle of my house. And thanks to node red and this project it is plugged into my heat pump system to know the indoor temperature.

But it is using a huge overkill device for what it is doing right now.

[emilic14]

I am marking this as answered to close the discussion as for my comments before.

If someone sees a new or can explain the correct usage of opentherm with a heat pump, then feel free to open a new discussion ^^.

[edterbak]

Just to note.
THere is an open therm pcb for heishamon.
I have absolutely no clue what it can do or how it works, and even IF the node red flow can interact with it.

https://www.tindie.com/stores/thehognl/

[geduxas]

Opentherm is protocol where talks thermostats and heating equipment in hardware level. It's unified protocol where could "talk" different brands/manufacturers in same language. It's 2 wire connection in hardware level, it works as serial/modbus/canbus.. so where could be node-red role in this.. I can't imagine.

[emilic14]

Yes, I actually have the big version of the heishamon card done by thehognl, which has opentherm.
But it is not really working with my Nest thermostat... And I only wanted to show the DHW temperature or send the Nest temperature to heishamon by opentherm cus I have access...
But as I reported here
There are many errors and its no working...

That said, as my system is all connected through Node-red... I dont really need opentherm :), but it would have been nice for my Nest display to know the water temp :)

[geduxas]

Ok, so your wires from nest should go to dedicated opentherm port of heishamon, and in heishamon should be enabled opentherm support. OpenTherm is open standard, so it should be treated same for all devices. Rest i think you should communicate with Ygor i think only he can help with that, he created board, and he extended heishamon for opentherm support. And i think it's nothing to do with node-red

[emilic14]

Exactly, and I have already done this :)

Noup, nothing to do with Node-red.
Everything to do with Heishamon.
And if it was working with Heishamon (it is not for the Nest, a lot of fail and errors), we could have included it in this node-red project which today is not using the opentherm data coming in from Heishamon...

Is this needed ? Not sure, hence me closing the discussion :)

[geduxas]

I don't think it's anyway possible to get data from opentherm.. it's different protocol, if you look it like mqtt but there is talking directly with device.. I don't think you benefit from this anyway... Nest device should request heishamon of particular data, and heishamon should respond to it.. also it should introduce what it can..

[emilic14]

Nest -- Opentherm -- Heishamon.
Heishamon -- mqtt -- Node-red.

->

Nest -- Opentherm -- Heishamon -- Mqtt -- Node-red.

Recovering the data is possible, and its already done between Heishamon -- mqtt -- Node-red.
The faulty part is the Nest -- Opentherm -- Heishamon , as discussed in the link I gave above for the Heishamon board that has the Opentherm option.

[geduxas]

What do you expect to get from nest to node-red in this link, or vice versa?