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NEST thermostat + radiant heat?

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Joined: Oct 12 2005

I tried the (free!) wireless thermostat that PG&E provided, but I'm finding it to be too unresponsive. (Ask it to do one thing, and it won't respond. I'm gone, but it's heating up the house unnecessarily.)

So I'm all into the idea of the NEST thermostat. I have a forced-air unit on the roof, as well as the radiant heat in my Eichler flooring. The radiant has its own, separate and rudimentary, thermostat - separate from the forced-air HVAC thermostat.

Version 2 of the NEST does recognize radiant heating, which is great. But I cannot find anything that tells me that I can combine the two thermostats into one.

Anybody out there can tell me that the NEST can run forced-air and radiant at the same time? Or anything else about the NEST unit that I should know?

Thanks!

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Joined: Nov 18 2012

We are also very interested in the NEST. This is our first winter in the house and I am unimpressed with the thermostat that came with the house. It cannot deal with the long heatup time of the radiant system and overshoots/undershoots quite badly. The house is freezing in the late evening and gets overly warm in the middle of the night. 

It seems like NEST should do a better job of this and I may just have to break down and try it. Version 2 is supposed to have "two stage" heat control where the primary heater (radiant) would be used most of the time and the secondary (forced air) would only come on if the temperature went some ways below the setpoint. This feature is intended for heat pumps so I am not sure that it will work with radiant heat and a forced air secondary.

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Joined: Oct 12 2005

I'm not asking about heat pumps. On their website NEST advertises "True Radiant:"

 

"True Radiant is a Nest exclusive feature that keeps homes with in-floor radiant or boiler-and-radiator systems more comfortable. It reduces temperature swings and starts heating early so you get the temperature you want when you want it.

True Radiant is a feature that Nest automatically activates for radiant systems. It keeps you more comfortable without using any more energy and gives you a predictable temperature on schedule. 

True Radiant is enabled automatically. To confirm or turn it off, follow these steps: On your Nest Learning Thermostat, go to Settings > Nest Sense > True Radiant and choose ON to enable it."

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Joined: Nov 18 2012

What I was trying to say is that I do not know if the "True Radiant" feature (designed for radiant) will work at the same time as "2 stage heating" feature (designed for heat pumps). Both working together would be required for both your radiant and your forced air system to heat the house together in a way that makes sense.

a_h
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Joined: Nov 12 2012

Yes, it does!

Our NEST works great with both our radiant and our HVAC, switching from one to the other as per the need...

We had it installed by a NEST certified installer a month back, and the installation was slightly pricey, but we have no regrets.. 

PM me for more details. 

Offline
Joined: Mar 9 2013

We tried to install a 1st gen Nest but our house doesn't have the right kind of voltage. Check before you buy!

On a related note - anyone want to buy our never-been-used 1st gen Nest? Unsealed box, but perfect condition. Send me a message if you are interested - joni.lindenstruth@gmail.com

:)

a_h
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Joined: Nov 12 2012

I want to clarify, I have one 2nd gen NEST thermostat controlling both the radiant and the HVAC.

ABG
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Joined: Apr 2 2013

I still had an original thermostat in my Eichler and the power line connecting it was line voltage. Joni i'm guessing this was also your case.
You can still install your Nest (which is low voltage, common these days) by adding a combo relay/transformer that transforms line voltage to low voltage. The one I bought was from Aube/Honeywell and it's the size of a deck of cards.

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Joined: Nov 23 2011

Can you post the wiring schematic you followed? I have the original 120v thermostat and would like to install a 2nd gen Nest. I just purchased a Honeywell ra89a and am looking at the wiring.

Online
Joined: Nov 13 2012

I discovered this issue as well. Nest 1.0 doesn't work with Radiant. No Nest works with line voltage (and original Eichler boiler setups use line voltage thermostats). As a result, Eichler owners with radiant and line voltage thermostats must purchase nest 2.0 AND convert the line voltage to low voltage using the relay/transformer that ABG references. I am about to start down this road in our RSM Eichler, and somewhere in the house those fat line voltage wires need to be skinny low voltage wires. My question is, where have people put the relay/transformer? Are you putting it in the wall behind the thermostat, or in the furnace room near the boiler and then using wire nuts at the thermostat to get a thinner gauge wire from the line voltage wires? Any insight would be great.

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Joined: Oct 16 2013

I just purchased a Nest 2nd generation and found out about the voltage issue. I am thinking about getting the Honeywell Relay RA89A and I can see the diagram on Fig 2 here: https://customer.honeywell.com/resources/techlit/TechLitDocuments/60-000...

Would you be so kind as to post some pictures of what your setup looks like, around the relay?

Thanks

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