Nest thermostats on a 2-wire system?

[farmantenna]

I don't know the details but power connectors have worked for me. Never heard back from the home owners. I figured it provided power to the Nest and used a communications signal to the Power connector that processed the signal to a discreet output

 

[hbiss]

I don't know the details but power connectors have worked for me. Never heard back from the home owners. I figured it provided power to the Nest and used a communications signal to the Power connector that processed the signal to a discreet output

No, nothing as exotic as that. I'm sure all it does is put suitable power on the W and R to the thermostat, when it's not calling, from the 24vac that's on the C and R on the boiler or furnace control.

Question is why is that thing such a power hog. Every other thermostat works fine.


-Hal

 

[Eddie702]

Most HVAC contractors I know hate Nest. They seem to be lees hateful against Ecobee.

 

[retirede]

Maybe they should stick with what they do best- spying on you.

-Hal

That’s what they do with the Nest. It’s all part of it.

 

[OldBroadcastTech]

Hal said " That's why most other thermostats use a couple of replaceable AA batteries. But that's so low tech."

But for some, its Oh So Much Trouble to pick up a couple of AA's on Sept 1 and replace them.....I have two Honeywell's and it takes 15 minutes to go get a 4-pack of the batteries and 5 minutes apiece to replace them.....Old Tech / Low Tech but it works......reliably.

 

[hbiss]

And if you use lithiums you'll get a few years out of them.

-Hal

 

[JoeNorm]

I fail to understand why people like Nest. You can't even set the thing on a vacation schedule. You have to trust it can read you mind.

Personally, I like the Honeywell IAQ thermostats that use the Redlink wireless. They only need two wires for power and all the communication to the HVAC unit is done wireless with a box mounted on/near the air handler. You can also get a Redlink gateway and use Honeywell's app, which does not require any subscription fees. It also can take various sensors like outdoor temp and duct before and after air handler temps. This can alert you to a problem.

Here is one example:

https://www.supplyhouse.com/Honeywell-Home-YTHX9421R5101WW-Prestige-IAQ-Kit-with-RedLINK-Includes-White-Thermostat-EIM-Wireless-Outdoor-Sensor-2-Duct-Sensors?review-page=2

Would there be any downside to this setup? Can you add thermostats for multiple locations? The system I am interested in applying it to is an electric boiler with radiators.

 

[hbiss]

Can you add thermostats for multiple locations?

"Electric boiler with radiators" doesn't tell us much. Multiple locations- do you mean zones? Does this system have zones with a thermostat for each now?

-Hal

 

[tthh]

Would there be any downside to this setup? Can you add thermostats for multiple locations? The system I am interested in applying it to is an electric boiler with radiators.

I've not used it on a boiler with individual zones, but I would imagine it works for that. You need to read the installation manual to see how that setup will work.

How exactly do you want it to work in a perfect world?

For example, my mother's house has a boiler with individual zones. There are inexpensive dumb Honeywell thermostats on the little used zones/rooms and the master bedroom and living area zones both have programmable thermostats.

 

[hbiss]

I've not used it on a boiler with individual zones, but I would imagine it works for that. You need to read the installation manual to see how that setup will work.

You need a separate thermostat for each zone!

-Hal

 

[JoeNorm]

Yes, It's multi-zoned. Not positive how many, probably 2-3. I am mopping this up after her HVAC contractor gave her a product she is unhappy with. So I am Just now seeing what is possible for her system and as you can tell i am not that familiar with how this all works.

So with that Honeywell system, I'd buy additional thermostats for each zone I wanted to be connected and programmable? From what I saw it was saying four wires are needed but I admit i have not deep dived into the manual yet.

 

[jim dungar]

The system I am interested in applying it to is an electric boiler with radiators.

The 60's era hydronic system in my old house had 'drive open' and 'drive closed' valves. I had to add double throw relays so that could I could use programmable stats in each zone. I then added a 3rd stat for the attic mounted AC. It was much less frustrating to have multiple cheap stats rather than a complex commercial grade control system.

 

[hbiss]

So with that Honeywell system, I'd buy additional thermostats for each zone I wanted to be connected and programmable? From what I saw it was saying four wires are needed but I admit i have not deep dived into the manual yet.

No, you wouldn't use that with that hydronic system. Get one of these for each zone. They can be programable or not. They will work with 2 wire or if you can get the C wire to it you don't need batteries.

https://www.supplyhouse.com/Honeywe...Thermostat-1H-1C-Heat-Pump-1H-1C-Conventional

-Hal

 

[hbiss]

The 60's era hydronic system in my old house had 'drive open' and 'drive closed' valves.

Zone valves?

-Hal

 

[tthh]

You have to know these things:
how many zones
how many thermostat wire conductors are available at each wall mounted thermostat
how many zones need to be programmable (as opposed, say to a not often used guest room)

Each zone valve will need to be controlled by something. Of course, the most common way is to have separate thermostats. I don't know about that one I mentioned, but I know there are some that can have extra room temperature sensors feeding the main thermostat and it will attempt to average the temps.

 

[hbiss]

I don't know about that one I mentioned, but I know there are some that can have extra room temperature sensors feeding the main thermostat and it will attempt to average the temps.

For commercial applications maybe. I did have commercial thermostats once where I added a remote sensor to one for a room that was for some reason colder. But that remote sensor setting disabled the sensor in the thermostat and you could only have one.

This is residential, why would you want to make it so complicated that you need an engineer to adjust it?

-Hal

 

[jim dungar]

This is residential, why would you want to make it so complicated that you need an engineer to adjust it?

My son had a home that had a Nest in the dining room off of the kitchen, on the east side out of the sun. He added a remote Nest sensor upstairs near his office which faced west. This worked for years until he could modify his duct work to include zone dampers.

 

[tthh]

For commercial applications maybe. I did have commercial thermostats once where I added a remote sensor to one for a room that was for some reason colder. But that remote sensor setting disabled the sensor in the thermostat and you could only have one.

This is residential, why would you want to make it so complicated that you need an engineer to adjust it?

-Hal

Totally agree to keep it as simple as possible, but really would like to know how the customer uses the system to understand what would be the best combination of design, cost, complexity.

 

[hbiss]

but really would like to know how the customer uses the system to understand what would be the best combination of design, cost, complexity.

Unless they are a techi, most of the time it will be that they just want to save money. That's the Nest's big claim, but most people who have it will say it fails to make much of a difference and the complexity isn't worth it.

-Hal

 

[jim dungar]

Unless they are a techi, most of the time it will be that they just want to save money. That's the Nest's big claim, but most people who have it will say it fails to make much of a difference and the complexity isn't worth it.

Yeah. That is true for almost all programmable stats in residential installs.