Two Thermostats One Zone

[cbrunny]

I have a one zone HVAC system on a two-storey-plus-basement setup. The basement is partially finished (not in progress) but often used. Thinking about adding a second thermostat to the basement. My existing thermostat is on the main floor and is a Nest.

In theory, adding a second to the basement would allow me to set the temperature in the basement. I understand this temperature would not be independent of the rest of the house. That's ok with me. The intent is to bring the basement up to temperature when I am down there.

Use case:
The Nest would be set at its own temperature. Say, 21C. The main floor is 21C and Nest is maintaining it.
Basement thermostat is switched to "off"
I go downstairs, where the temp is actually 16C. I switch the thermostat on to 20C.
Furnace kicks on bringing basement to 20C, also increasing temps in rest of house.
In my case, I would only switch on the basement thermostat when I am in the basement. I would switch it off when I am not.

I'm far from expert. What am I missing? It's a forced air system that is relatively recent. House was constructed in 2010.

 

[highland145]

We have a similar pile of crap setup with a heat pump. Was not what I wanted when we bought the new unit about 6 years ago. I wanted zone dampers for the up/downstairs. So if I wanted cold upstairs, the dampers would automatically close for the down and visa versa. I blame the installer for not educating me or knowing what he was doing.

So what happens now is I have to close/open the registers depending on the time of year. Turn off the downstairs thermostat for the summer and the upstairs one for the winter. PITA.

When this unit craps out, I will be getting 2 separate units.

Have you thought about something like a Mr. Slim?

 

[nickbits]

Use the remote control feature of the nest. I don't think they make a way for two stats to control one zone.

 

[cbrunny]

I thought about just using the remote feature of the Nest. It's great and works well, but it doesn't tell you the temperature of the room you are in. Also, if I turn it up in the morning and then stay down there for a few hours, the Nest goes into away mode and doesn't heat. It can be deactivated from my phone no problem but i don't get a notification that it is in away mode.

 

[cbrunny]

I hadn't thought about a Mr. Slim, but I'm trying to be as cheap as possible on this. Seems that with a basic thermostat and wiring, I could do this myself for under $100 easy. That is, assuming my logic is correct and its even possible.

 

[richardycc]

you can do it, just wire them in series, but it won't work as how you want them to. Both thermostats will need to be calling for heat for the heat to come on, as soon as your first floor temperature is higher than the first floor set point, it will shut off the heat, your basement might still be too cold. Until you jack up your first floor temperature set point higher first to like 30C every time you go down to the basement.

Honeywell has a Redlink thermostat with remote sensor/controller that will work in your situation, but it's expensive, over $300.

 

[Belegost]

you can do it, just wire them in series, but it won't work as how you want them to. Both thermostats will need to be calling for heat for the heat to come on, as soon as your first floor temperature is higher than the first floor set point, it will shut off the heat, your basement might still be too cold. Until you jack up your first floor temperature set point higher first to like 30C every time you go down to the basement.

Honeywell has a Redlink thermostat with remote sensor/controller that will work in your situation, but it's expensive, over $300.

Why not just wire them in parallel? Or if isolation is desired (and with the Nest it might be preferable) a 12V OR gate would do.

 

[Kaido]

I have a one zone HVAC system on a two-storey-plus-basement setup. The basement is partially finished (not in progress) but often used. Thinking about adding a second thermostat to the basement. My existing thermostat is on the main floor and is a Nest.

In theory, adding a second to the basement would allow me to set the temperature in the basement. I understand this temperature would not be independent of the rest of the house. That's ok with me. The intent is to bring the basement up to temperature when I am down there.

Use case:
The Nest would be set at its own temperature. Say, 21C. The main floor is 21C and Nest is maintaining it.
Basement thermostat is switched to "off"
I go downstairs, where the temp is actually 16C. I switch the thermostat on to 20C.
Furnace kicks on bringing basement to 20C, also increasing temps in rest of house.
In my case, I would only switch on the basement thermostat when I am in the basement. I would switch it off when I am not.

I'm far from expert. What am I missing? It's a forced air system that is relatively recent. House was constructed in 2010.

So basically:

1. You have a 1-zone HVAC system
2. You have a Nest Thermostat on the main floor
3. You want a second thermostat in the basement to set the temperature in the basement when you are physically in the basement (knowing that it is not independent of the rest of the house)

I see 3 options:

1. Buy a second Nest ($$$)
2. Buy a second regular thermostat ($$)
3. Buy a tablet to keep in the basement & use the Nest app ($$)

Nest allows for two usage scenarios in this situation: one, using multiple Nest Thermostats within a single home, and two, using a Nest Thermostat with a non-Nest Thermostat. More info here:

https://nest.com/support/article/Ho...le-Nest-Learning-Thermostats-in-the-same-home

While Nest Thermostats work just fine with regular thermostats, your home benefits from additional features when every thermostat is a Nest Thermostat.

Alternatively, you could just buy a cheap tablet & keep that in the basement to control the HVAC system using the Nest app. Newegg has a basic 7" tablet for $70:

http://www.newegg.com/Product/Produc...82E16834757022

The Nest app is free:

https://play.google.com/store/apps/details?id=com.nestlabs.android&hl=en

Granted, while a tablet is cool, a fixed thermostat is something that is straightforward to use & doesn't grow legs

 

[cbrunny]

I actually contacted Nest about this to find out if it would work the way I wanted. That would be the ideal. They said the only way it would work is if I had the second nest set up under a different account so that the two would not work together. It seemed like too much risk for the cost of a Nest when I could really just do the same with a cheapo thermostat. When you have two nests they can probably schedule differently, but I the auto-away would not flip on in the basement because it would detect me on the main floor.

And now that I think about it, I might still have the old thermostat that I had before the Nest kicking around here somewhere. Then all I'd need is some cheap wiring. $15 to test it out, and possibly resolve it... worth doing imo if I can find it.

 

[cbrunny]

Why not just wire them in parallel? Or if isolation is desired (and with the Nest it might be preferable) a 12V OR gate would do.

what's the difference between parallel and series? (noob). What's a 12V and gate? (ubernoob).

My plan is to just wire it directly to the furnace. everything is exposed so that's by far the easiest option I have. I'm assuming that's what you mean by parallel, and series would be something like Nest-->new-stat-->furnace in one... well.. series.

Logically to me it makes sense that in parallel (my understanding, which may be totally wrong) this would work.

 

[Belegost]

what's the difference between parallel and series? (noob). What's a 12V and gate? (ubernoob).

My plan is to just wire it directly to the furnace. everything is exposed so that's by far the easiest option I have. I'm assuming that's what you mean by parallel, and series would be something like Nest-->new-stat-->furnace in one... well.. series.

Logically to me it makes sense that in parallel (my understanding, which may be totally wrong) this would work.

You have the right idea for series and parallel.

As for the 12V and gate - I was a bit mistaken, I had thought thermostat control lines were 12V DC, but I decided to check it out, they are usually 24V AC it seems. In which case isolation becomes far less of an issue, since the thermostat must already have logic circuitry isolated from the control line.

 

[Kaido]

I actually contacted Nest about this to find out if it would work the way I wanted. That would be the ideal. They said the only way it would work is if I had the second nest set up under a different account so that the two would not work together. It seemed like too much risk for the cost of a Nest when I could really just do the same with a cheapo thermostat. When you have two nests they can probably schedule differently, but I the auto-away would not flip on in the basement because it would detect me on the main floor.

And now that I think about it, I might still have the old thermostat that I had before the Nest kicking around here somewhere. Then all I'd need is some cheap wiring. $15 to test it out, and possibly resolve it... worth doing imo if I can find it.

Well that's stupid. They should have an option for the Nest to be a slave to the main one via Wifi, especially since they have an entire webpage about having multiple units work together. Boo Nest :thumbsdown:

Wink actually has a pretty smart idea...they have a thermostat called the Norm that integrates sensors in every room (Spotter v2 & Relay) to give a more balanced output. Next step is integrating that technology into HVAC systems. The Mr. Slim is still sorely lacking in quality wireless control, although motorized "smart" vents are starting to come out for traditional air systems, which is pretty cool. Micro-zoned heat & A/C, whoo!

 

[cbrunny]

There's also the more expensive WallyHome which solves this entirely and works with nest, but pricey and difficult to come by in Canada.

 

[cbrunny]

Well that's stupid. They should have an option for the Nest to be a slave to the main one via Wifi, especially since they have an entire webpage about having multiple units work together. Boo Nest :thumbsdown:

There's a really good post on their support website where some guy thoroughly proposes what he calls a NestEgg, which is basically a nest that plugs into a wall socket and provides the remote temperature info to the main unit connected to the furnace. I'd be surprised if they're not working on it or similar, but it really can't come fast enough. I'd buy three.

 

[Kaido]

There's a really good post on their support website where some guy thoroughly proposes what he calls a NestEgg, which is basically a nest that plugs into a wall socket and provides the remote temperature info to the main unit connected to the furnace. I'd be surprised if they're not working on it or similar, but it really can't come fast enough. I'd buy three.

Yeah, that'd be smart. They should make that & also buy Linq, which is getting crowdfunding for smartvents:

https://www.kickstarter.com/projects/linqhome/automated-comfort-linq-smart-vents

Short of a complete HVAC overhaul for multiple zones ($$$), this would be the next best solution...spend a few hundred bucks on a some thermostats, sensors, and wireless motorized vents.

imo they should definitely add multiple Nest support (which is weird since their website says that's supported), or create another product that doesn't have wiring hookups to the HVAC system, that just acts as a wall-mounted controller - Nest Lite or something.

 

[pmark]

you can do it, just wire them in series, but it won't work as how you want them to. Both thermostats will need to be calling for heat for the heat to come on, as soon as your first floor temperature is higher than the first floor set point, it will shut off the heat, your basement might still be too cold. Until you jack up your first floor temperature set point higher first to like 30C every time you go down to the basement.

Honeywell has a Redlink thermostat with remote sensor/controller that will work in your situation, but it's expensive, over $300.

Does anyone have any experience with the Honeywell Redlink thermostat?

 

[richardycc]

Does anyone have any experience with the Honeywell Redlink thermostat?

I have the original Prestige system with Redlink technology for 3-4yrs now, added the internet gateway few years ago, very reliable, don't think I've ever lost connection between the app and the thermostat. I'd use it in a vacation house. Their Lyric, which I added to one of my zones 2 weeks ago isn't as reliable, think I've lost connection 2-3 times already.

 

[cbrunny]

So I dug up my old thermostat. It's a decent one, programmable, but I don't really need it to be fancy. I ran to Home Depot to grab some thermostat wiring and hooked it up in parallel with the nest. So far, so good. Everything seems to be working properly and how I expected it to. Early indicators are success.

When one thermostat calls for heat or fan, the other does not recognize the heat or fan. I set the basement thermostat to reset to 10C every morning, just in case I forget to turn it off. It has a "run schedule" button on it, so when I run up the stairs all i have to do is push it and it will revert back to 10C. The Nest seems to have no issue with it at all. When the basement is set to 10C, the Nest keeps the temperature up.

So, two parallel thermostats in one zone is a success!

 

[shabby]

The other solution to this is an ecobee3, you get an additional sensor with it where you can disable the main thermostat and use the sensor as the temp sensor. Or you can set it where it'll average the temps between the two or more sensors if you have them.

 

[gisnar]

I have a one zone HVAC system on a two-storey-plus-basement setup. The basement is partially finished (not in progress) but often used. Thinking about adding a second thermostat to the basement. My existing thermostat is on the main floor and is a Nest.

In theory, adding a second to the basement would allow me to set the temperature in the basement. I understand this temperature would not be independent of the rest of the house. That's ok with me. The intent is to bring the basement up to temperature when I am down there.

Use case:
The Nest would be set at its own temperature. Say, 21C. The main floor is 21C and Nest is maintaining it.
Basement thermostat is switched to "off"
I go downstairs, where the temp is actually 16C. I switch the thermostat on to 20C.
Furnace kicks on bringing basement to 20C, also increasing temps in rest of house.
In my case, I would only switch on the basement thermostat when I am in the basement. I would switch it off when I am not.

I'm far from expert. What am I missing? It's a forced air system that is relatively recent. House was constructed in 2010.

Assuming there is a cold air return in the basement, a simple solution is to just run the furnace fan all the time to even out the temperature on the main floor and in the basement - no additional thermostat is required. However, this is not a great idea and I wouldn't do this on an ongoing basis.

What I would do instead is to add another (simple) thermostat in the basement, but only have it act on the furnace fan. In other words, the ON/OFF of the furnace fan would be controlled by the furnace heat (furnace fan starts when the heat comes on and stops when the heat shuts off) OR the basement thermostat. The two signals would be wired in parallel.

Use case:
The main floor thermostat is set to 21C. The main floor temp is 21C and the thermostat is maintaining it.
Basement temp is 16C and the basement thermostat is set to 16C or below.
Then the basement thermostat is set to 21C. The furnace fan will turn on since the setpoint of the basement thermostat is above the actual temperature.
This will circulate air in the whole house. The basement temp will rise and the main floor temp will drop.
This will turn on the furnace bringing the temp back up to 21 C on the main floor and make the basement temp rise a bit more. When the heat turns off, the furnace fan is still running since the basement temp is still below 21C. This cycle of ON and OFF of the heat will repeat itself. The main floor temp will be maintained at 21C and the basement temp will gradually rise. Only when the basement temp reaches 21C (or whatever temp the basement thermostat has been set to between 16C and 21C) will the furnace fan turn off.

I have not tried this scheme, but believe it should work. I'm thinking of trying it in my own house.

 

[DrPizza]

For about $150, you can get a ventless gas space heater. Another $50 for installation materials. So, $100 more than you were looking to spend. However, you'd probably save quite a bit of money by not overheating the house for the sake of having the basement warm while you're down there. If you have a very new house that's pretty air tight - don't do this. If your house is more than 60 years old, it's quite doable. In between... depends on how airtight your house actually is.

 

[shabby]

you can get a ventless gas space heater.

Only if you intend to wear a gas mask when using it then sure, otherwise don't.

 

[DrPizza]

Only if you intend to wear a gas mask when using it then sure, otherwise don't.

Not sure why you'd say that. There's very little difference between that to heat a smaller area & a kitchen getting warmer because you're cooking a turkey (in a natural gas oven).

 

[Red Squirrel]

I would just get a basic thermostat and wire it in parallel with the tstat wire. Only thing, if your house is as badly insulated as mine, if the basement actually reaches 22 it's going to be ridiculous upstairs lol.

Another option is adding some kind of damper in the main trunk that just pushes a huge chunk of the air into the basement. May require some duct work and some mechanical work, like micro controller controlling a servo or actuator. Have the thermostat control the damper furnace and the damper. So it turns furnace on, and the damper. When temp reaches set point, it turns damper and furnace on. The nest upstairs, if it's calling for heat, will just make it so the furnace stays on but damper goes back to normal, so air will then start to go upstairs.

If basement is isolated from upstairs (ex: door) you'll want to make sure you have a return down there as well if you do something like this.

 

[shabby]

Not sure why you'd say that. There's very little difference between that to heat a smaller area & a kitchen getting warmer because you're cooking a turkey (in a natural gas oven).

Whats above every oven?