topic Nest 3rd Gen and Opentherm on S Plan system in Nest Thermostats

Nest 3rd Gen and Opentherm on S Plan system

gingham-foliage — Wed, 23 Mar 2022 21:53:08 GMT

Hi,

I'm interested in using a Nest 3rd gen with my Opentherm system boiler that is configured in an S plan setup. The wiring guide does not show this installation. Is it possible to do?

Thanks,

Theo

Re: Nest 3rd Gen and Opentherm on S Plan system

DragosC — Thu, 24 Mar 2022 13:15:19 GMT

Hi there @gingham-foliage.

Thanks for reaching out. The thermostat has instructions for Combi OpenTherm only or system boiler with on/off. Could you tell us please if you've checked with the compatibility widget from our website? Here's the link for that: https://bit.ly/2ZOmnxX .

Re: Nest 3rd Gen and Opentherm on S Plan system

gingham-foliage — Thu, 24 Mar 2022 13:52:51 GMT

Thanks for the link to the site. It says the system is compatible, but does not mention OpenTherm. Has anyone used Opentherm with a system boiler that is configured in S plan (or Y plan for that matter)?

Re: Nest 3rd Gen and Opentherm on S Plan system

DragosC — Thu, 24 Mar 2022 13:59:42 GMT

Great. The OpenTherm is not compatible with the S or Y plan. Those are on/off motorized valves. The OpenTherm modulation does not have valves for on/off. We're interested in the fact if the boiler was originally OpenTherm or is it a system boiler with an OpenTherm additional module installed after?

Re: Nest 3rd Gen and Opentherm on S Plan system

gingham-foliage — Thu, 24 Mar 2022 14:08:22 GMT

It's for a boiler that has an additional module installed. My understanding is that these are usually configured so that the OpenTherm protocol is used to control the power (modulation) of the boiler, and the controller is still used to activate the appropriate valves. I've read on forums that Nest Heat Link will still activate the relays even when the Nest is in OpenTherm mode, allowing the valves to operate, and the boiler to module the power.

Are boilers with additional modules different from boilers with it fitted from the factory?

Re: Nest 3rd Gen and Opentherm on S Plan system

DragosC — Thu, 24 Mar 2022 14:14:02 GMT

Thanks for the explanation. In this case, it's not compatible with the OpenTherm part, just with the on/off settings system boiler. The Nest Thermostat is compatible just with the Combi boiler OpenTherms that are like that from factory. You can learn more about what can the Nest Thermostats do with the OpenTherm combi boilers: https://bit.ly/3HeJohK

Re: Nest 3rd Gen and Opentherm on S Plan system

AlexD — Sun, 27 Mar 2022 12:47:55 GMT

Hi, I wanted to check in. Do you need any further assistance? If so, make sure to let me know.

Re: Nest 3rd Gen and Opentherm on S Plan system

gingham-foliage — Mon, 28 Mar 2022 12:57:46 GMT

It would be great to know if the Nest Heat Link will still activate the relays even when the Nest is in OpenTherm mode

Re: Nest 3rd Gen and Opentherm on S Plan system

DragosC — Tue, 29 Mar 2022 11:26:10 GMT

The relays are activated by the On/Off function. The OpenTherm does not have anything to do with the relays. The OpenTherm keeps the system always on on different intensities.

Re: Nest 3rd Gen and Opentherm on S Plan system

gingham-foliage — Tue, 29 Mar 2022 14:17:59 GMT

Sorry, I'm so confused are you saying that the relays will continue to operate even when True Radiant is enabled - as they have nothing to do with one another. Or are you saying the opposite?

Re: Nest 3rd Gen and Opentherm on S Plan system

DragosC — Wed, 30 Mar 2022 12:53:41 GMT

I'm sorry for the confusion. The information is better explained here about the differences between the relayed heating and OpenTherm heating. Please take a look at it: https://bit.ly/3HeJohK

Re: Nest 3rd Gen and Opentherm on S Plan system

AlexD — Sat, 02 Apr 2022 13:09:00 GMT

Hi, I wanted to check in. Do you need any further assistance? If so, make sure to let me know.

Re: Nest 3rd Gen and Opentherm on S Plan system

george_t — Mon, 04 Apr 2022 13:19:18 GMT

It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.