Verify CH Load Compensation / Modulation (revisited) - OpenTerm

[ydrol]

In this thread I was told Google Nest cannot change settings on the boiler

[ link https://www.googlenestcommunity.com/t5/Nest-Thermostats/Verify-CH-Load-Compensation-Modulation/td-p/... ]

But according to this page it can if it is OpenTherm icompatable: https://support.google.com/googlenest/answer/9259109?hl=en-GB 

"With OpenTherm, the Nest thermostats listed above can control both your boiler’s domestic hot water temperature, as well as the temperature of the water used to heat your home."

"

The boiler will use more or less gas, as appropriate, to reach the water temperature set by the thermostat.

Since your Nest thermostat will tell your OpenTherm compatible boiler how to modulate when True Radiant is enabled, your heat may run for long periods of time but the water used for heating will be set to a lower temperature."

[Olafmol]

What's your question exactly? Happy to try and answer. OpenTherm specs can ask the boiler to heat water to a certain temperature. Depending on your boiler specs, this can be either for the heating system, for the hot water system, or both. Over here in the Netherlands, typically the boiler itself sets the warm water system temperature, as this is a fixed temperature. The heating system water temperature can be dynamic, as modulating systems like TrueRadiant typically start with a higher temperature, and then decrease the temperature when the thermometer starts to reach the set-point.

[ydrol]

No question, just a clarification.

I previously asked on this forum if the Nest can modulate the boiler. I was told "no", but as I understand it - OpenTherm+TrueRadiant means Nest can modulate the boiler output and flow temps. Seeking clarification , and how to confirm if the Nest is set up this way?

[Olafmol]

By enabling TrueRadiant, you enable OpenTherm modulation. You will see the Nest requesting a high(er) water temperature from your boiler, and over time it will decrease the requested water temperature. You can see this happening in your boiler info/monitoring. It only modulates the requested heating water temperature btw. If you disable TrueRadiant, the Nest switches to On/Off heating.  

[EdwardT]

Hi folks,

@Olafmol, thanks for the help!

@ydrol, I hope that Olafmol's response answered your question. Let us know if you have other questions and we'd be glad to assist.

Thanks,

Edward

[Jeff]

Hey Olafmol,

I just wanted to follow up once more to see if you were still needing some help here. If so, just let us know.

Thanks,
Jeff

[Jeff]

Hi everyone,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Jeff