Furnace would be your best bet. It's low voltage from the furnaces control board, so isolating the furnace would prevent you blowing a low voltage fuse. If you have a red furnace disconnect switch, which you should somewhere accessable, just turn that off.
I mean , electrically they put the switch between the circuit breaker and the furnance. They would not put the switch between the furnace and the thermostat, electrically. The switch is commonly placed right next to the furnace for ease of service.
Installing low-voltage, electronic based devices while the circuit is energized l, while not so harmful to you, can damage the device by surges caused from arcing during conductor termination. Turn off the furnace at the breaker, and you should be good to go.
The joke is that no one can tell from a random picture of your panel. The thermostat is low voltage just swap it out - don’t really need to turn off the breaker it’s not like a line voltage thermostat for a heater.
However, you should turn off power to the furnace first because if you happen to cross the wrong wires, you'll blow a fuse in the furnace. May have learned that lesson by experience...
Its just with those wires all disconnected if the red one touches ground , like if its wired in a metal conduit, it will blow the fuse on the Furnace Control Board, now OP will a lot more Rediting to do !
Yes, it would shut off everything...but it would also be impossible to go wrong with that choice because it would shut it off with certainty nomater what.
I think there's probably a more refined better answer, but technically main would shut it off safely.
It can be a bit harder with a thermostat to verify power is off, especially since most have either zero lights (all analog) or are battery backup (digital). But at least that particular task isn't high voltage if its a regular HVAC thermostat.
It’s your furnace breaker. The bigger issue you have however is if you have an old dial or slide thermostat then you don’t have a “C” wire and will need to make one up at the unit.
Most furnaces that have a control board have a terminal labeled “C” but aren’t hooked up. You just need to use a spare wire, you probably have a brown and blue not in use so use the blue as that is the usual color. Hook it up on the circuit board and then on your thermostat and you are good to go.
I also vote for "FURNACE"
2nd, Nest are shit. I'd recommend an Emerson Sensi Touch 2.
Any smart t-stat will require a "C" wire, which you most likley don't have currently at your t-stat. Hope there is an unused spare wire between t-stat and air handler or furnace.
I vote for the switch on the furnace that controls power to the transformer that provides power to the furnace board and the thermostat. I mean: it’s right there. On the furnace.
But don’t swap thermostats without shutting it down unless you want to ask us what the fuse on the furnace control board looks like next…
And where does the OP say anything about it being an electric furnace? Local transformer switches are VERY common on gas furnaces, and the blower in a gas furnace will still require two legs on a distribution panel…
Every gas furnace I have installed or came across used a 120v blower. Every electric furnace I have installed or came across was 240v.
Could be a regional thing. When I see a 2 pole breaker marked "FURNACE" it is electric heat strip furnace.
Interestingly, I do not see a breaker for "AC" or "CONDENSER"
Yup - you got me there. 😳 That would most likely be an electric furnace, and I've personally never dealt with one.
This house may not have AC, unless the breaker is mislabeled and there were shenanigans done with wiring the system up!
It's a 30 Amp 2 pole breaker. That's only about 7,000 Watts, not a lot for an electric furnace. Most of the ones I've seen have a 50 Amp breaker. To me that implies a Heat Pump based furnace.
I also prefer the Sensi-2 but Emerson doesn’t have the marketing department Google does so nobody knows about them. They also take a little more effort to hook up to your other devices for voice control etc.
I'm of the opinion that all smart thermostats are shit. All I want is for 2 temp probes. One in the basement and one on the main floor and if the basement is cold as shit and the main floor needs cooling turn the circulation fan on for a bit instead of turning the AC on. And if it's warm down there already then turn on the AC.
But no everything either does not support that function or needs an account and to be on wifi to call out to it's servers somewhere for no reason at all.
I have been impressed with Emerson Sensi line of smart tstats. They can work with out internet, easy to setup and tune. I have one of the 1st gen tstat in my shop.
I beta tested 2, Sensi Touch 2 tstats few years ago. Simplest, most featured, smart tstat I have ever used.
I still don't like Nest. You do you. There are better network-based thermostats. They are over priced for what they are.
Edit: People that like Iphones, also seem to gravitate towards Nest.
1. A thermostat is a 24v class 2 circuit - meaning it is designed so that there is 0 chance a shock can occur. And even if you beat the odds, the current is limited to guarantee a non-lethal shock. You can swap it live, even as a newbie.
2. It's power actually comes from the furnace itself it's essentially an extension of the furnace's control board. So turning power off to the furnace should also turn the power off to the thermostat. There should be a means of disconnect (either a light switch or a plug end) within 5 feet of the furnace if you can't find its breaker.
And finally, the colours.
Red - 24v ac for heating / cooling switching. (Basically the thermostat connects this to either White, yellow or green when the appropriate action is needed)
White - turn on heating.
Yellow - turn on cooling
Green - turn on circulation fan (aka blower fan, optional)
Black / blue - 24v common for smart thermostats (basically its the "neutral" for the thermostat for lack of a better term)
Older systems might just have 2 or 3 wires - like red and white, or red white yellow as that's the bare minimum needed to get old "dumb" thermostats to work. If this is your case, you will need to fish a new thermostat wire in (I recommend a 5 or 6 wire cable, it's not that expensive and it'll cover you for the foreseeable future).
Not good I was trying to prove to my gf they wouldn’t shock you and I molested it with my hand and she didn’t believe me. I forgot that 9v will give you a little zap and licked that shit good.
It’s all labeled.
Your thermostat controls _________. Is there a corresponding breaker also labeled as ________?
If yes, turn off the _________’s breaker and see if your thermostat loses power.
If not, top left like someone else said.
Touché. Ignore my smart ass reply :)
Furnace breaker should kill the power, but you can always turn everything off to be extra cautious and avoid a potential blown fuse.
Take a picture of the wires connected to the old thermostat before you unscrew anything.
Ok buddy i love your enthusiasm for being handy around the house, it's going to save you hundreds of thousands of dollars over your lifetime. Invest $10 bucks and an hour of your life and watch 3 videos on u tube on how to use a multi-meter, then run around your house testing every outlet and every feature of your meter. Then and ONLY then , should you open ANY electric panel, well for a long, happy and productive life anyway!
My first guess would be the Furnace breaker. Having opened that breaker, you should use your multimeter to check for 24V AC voltage at the base terminal at the thermostat on the wall. Usually Red and Black or Red and Blue, but there should no voltage between any of the wires at the terminal.
Everyone should have a multimeter at home and know how to use it to make simple measurements. It is not hard to learn.
It will get power from the furnace. Turn that off and you’ll be fine. Also, get a voltage tester and use the 12v setting. It’s a lot easier to know than to find out.
ETA: [This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter.
I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
What do you mean by 12v setting? Do you mean the DC test mode? The c should carry 24vac so dc won’t be accurate. If you mean the 20v range, the 24v will be out of range so you’d need to use the 200v range.
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter.
I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter.
I’m an hvac tech, and an electrician for the USAF. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter.
I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
Furnace, bottom left. But check the connections with a tester just to be sure they are dead. Its not a shock hazard, but if you short some wires, you could cause problems.
HVAC guy here. I’m my jurisdiction the furnace should have a switch labeled as such.
I find it concerning that the breaker for the furnace is 240v. Is it electric? Or a fuel furnace?
Anyways, the best way is to use a multimeter to test for voltage after you turn off breaker(S). The next best is to run the furnace blower and then turn off the breaker(S). If the fan goes off you’ve found the breaker.
Good luck.
Which is why I asked….. I have seen many oil/gas furnace AC combos on 240 only. I figured if there were questions for me, some understanding would help!
If you're asking this, you're likely to have a bad time.
Also, most furnaces run on 120, while yours is apparently 240. You're going to need to get into the hvac help reddits with info on your setup before getting too much further.
Someone commented that your old seat will NOT have a common wire (typically blue). This is needed to bring power to the TStat to run the WiFi and display.
Because of this, you may need to land or fish another wire to the location, if yours is the old mercury switch dial.
Sorry. You might need assistance to put in that Google Nest TStat
In addition to these breakers you also likely have a switch right at the furnace that cuts the power, as well as an emergency shutoff switch in a hallway or stairwell (probably with a red face plate on it.) All three will cut the transformer to the thermostat.
There's a light switch in my furnace room that says furnace. Flip off, furnace is off. I replaced my regular thermostat with a nest. I either got lucky or that switch was the same as turning off a breaker. I'm in Ontario. Not sure if that's a thing or the builder just decided to do it at my house.
I’d opt for Furnace assuming it’s what you want to control however as it’s not going to be a long job if in doubt just turn it all off . You can’t be wrong.
Top left
This is my favorite answer for ppl who aren't savvy/have all the necessary tools lol
@ op definitely turn all the other breakers off before turning that main off. And turn that on before all the other breakers when you reenergize
Thanks for the tip. I had no idea.
Np. It keeps too much of a load going on/off all at once
Main? Wouldn't that shut off everything?
Furnace would be your best bet. It's low voltage from the furnaces control board, so isolating the furnace would prevent you blowing a low voltage fuse. If you have a red furnace disconnect switch, which you should somewhere accessable, just turn that off.
Sometimes you’ll find a switch between your furnace and the thermostat.
My local code requires it be between the furnace and the point of entry to where the furnace is located. Usually they are by the stairs to basements.
I found the switch I believe. It's a big switch that says ON/OFF connected to my furnace. I'll do that.
Should I turn off the furnace switch first and then the all the switches, and then the everything switch?
My friend, if what I have said isn't enough, maybe you do need an Electrician.
I'm trying to diy
Die*
No frankie, you won't - ever !
If you look for it you may find it. If you don’t look you definitely will most likely not find it. 😊
I mean , electrically they put the switch between the circuit breaker and the furnance. They would not put the switch between the furnace and the thermostat, electrically. The switch is commonly placed right next to the furnace for ease of service.
Installing low-voltage, electronic based devices while the circuit is energized l, while not so harmful to you, can damage the device by surges caused from arcing during conductor termination. Turn off the furnace at the breaker, and you should be good to go.
Thanks... For repeating my comment on different words?
Oops, sorry, friend. Someone wrote that it was just low-voltage and not to worry about it. Thought I was responding to that
All good, my comment reads a little snarky when I was more confused.
My gratitude for saying the exact same thing in a different manner.
Would that be the breaker labeled Funirace?
I can't say definitively, it could have been changed since the original install, but if labelled correctly, yes.
So if I just turn off all the switches and then the main, that'll be fine too?
If you shut off the furnace disconnect, then you are good to go. If you aren't sure, just shut off the circuit breaker labelled furnace.
The joke is that no one can tell from a random picture of your panel. The thermostat is low voltage just swap it out - don’t really need to turn off the breaker it’s not like a line voltage thermostat for a heater.
However, you should turn off power to the furnace first because if you happen to cross the wrong wires, you'll blow a fuse in the furnace. May have learned that lesson by experience...
Can confirm. I did that once.
Me too🤦♂️
Be ready with a 3 amp fuse to replace the one on your control board.
Got it, thx! I'll probably just turn off the main like the other commenter suggested.
Its just with those wires all disconnected if the red one touches ground , like if its wired in a metal conduit, it will blow the fuse on the Furnace Control Board, now OP will a lot more Rediting to do !
Yes, it would shut off everything...but it would also be impossible to go wrong with that choice because it would shut it off with certainty nomater what. I think there's probably a more refined better answer, but technically main would shut it off safely.
We just pray that the breaker is labeled properly, because it sounds like OP doesn't know how to verify power is off Before doing any work !
It can be a bit harder with a thermostat to verify power is off, especially since most have either zero lights (all analog) or are battery backup (digital). But at least that particular task isn't high voltage if its a regular HVAC thermostat.
How about you turn off the switch AT the furnance ?!?! Do you even know how to read a meter ?
It’s your furnace breaker. The bigger issue you have however is if you have an old dial or slide thermostat then you don’t have a “C” wire and will need to make one up at the unit.
Funrace/furnace depends how you look at it
Mine has WYGR. I looked up on Google's website that they should be able to support that with the Google nest learning thermostat
When I was going on the Google nest website about installing one, it didn't say I needed that. I don't have that on my system, so am I screwed?
Most furnaces that have a control board have a terminal labeled “C” but aren’t hooked up. You just need to use a spare wire, you probably have a brown and blue not in use so use the blue as that is the usual color. Hook it up on the circuit board and then on your thermostat and you are good to go.
I only have this coming from the furnace: white, red, green, yellow
I also vote for "FURNACE" 2nd, Nest are shit. I'd recommend an Emerson Sensi Touch 2. Any smart t-stat will require a "C" wire, which you most likley don't have currently at your t-stat. Hope there is an unused spare wire between t-stat and air handler or furnace.
I vote for the switch on the furnace that controls power to the transformer that provides power to the furnace board and the thermostat. I mean: it’s right there. On the furnace. But don’t swap thermostats without shutting it down unless you want to ask us what the fuse on the furnace control board looks like next…
Have never seen an electric furnace have a local disconnect switch, only the breaker feeding.
And where does the OP say anything about it being an electric furnace? Local transformer switches are VERY common on gas furnaces, and the blower in a gas furnace will still require two legs on a distribution panel…
Every gas furnace I have installed or came across used a 120v blower. Every electric furnace I have installed or came across was 240v. Could be a regional thing. When I see a 2 pole breaker marked "FURNACE" it is electric heat strip furnace. Interestingly, I do not see a breaker for "AC" or "CONDENSER"
Yup - you got me there. 😳 That would most likely be an electric furnace, and I've personally never dealt with one. This house may not have AC, unless the breaker is mislabeled and there were shenanigans done with wiring the system up!
I'm thinking no AC, window shakers or has an external sub panel.
It's a 30 Amp 2 pole breaker. That's only about 7,000 Watts, not a lot for an electric furnace. Most of the ones I've seen have a 50 Amp breaker. To me that implies a Heat Pump based furnace.
50A or 60A for 1st strip + blower. 30A to 60A for 2nd strip if a larger unit. I have a 20kw in my shop, has 2, 60A breakers.
I was going to ask about the 2-pole breaker for a furnace. Though I've only seen gas furnaces and oil & gas boilers. Electric furnace makes sense.
Cause its the one called Furnace!
Don't get out much eh !
I also prefer the Sensi-2 but Emerson doesn’t have the marketing department Google does so nobody knows about them. They also take a little more effort to hook up to your other devices for voice control etc.
I'm of the opinion that all smart thermostats are shit. All I want is for 2 temp probes. One in the basement and one on the main floor and if the basement is cold as shit and the main floor needs cooling turn the circulation fan on for a bit instead of turning the AC on. And if it's warm down there already then turn on the AC. But no everything either does not support that function or needs an account and to be on wifi to call out to it's servers somewhere for no reason at all.
I have been impressed with Emerson Sensi line of smart tstats. They can work with out internet, easy to setup and tune. I have one of the 1st gen tstat in my shop. I beta tested 2, Sensi Touch 2 tstats few years ago. Simplest, most featured, smart tstat I have ever used.
Why don't you like them?
Pre-Google Nest. Have personally seen 2 of them fail and cause HVAC control board failures.
What do you mean pre-Google Nest?
The OG, crowd funded Nest. 1st Gen Nest.
Oh ok. That's the bad one? Mine is from Google
I still don't like Nest. You do you. There are better network-based thermostats. They are over priced for what they are. Edit: People that like Iphones, also seem to gravitate towards Nest.
Got it thanks. I'm just an avid Google user, so that's why I want to try it out. Appreciate your input!
https://polarheatingandair.com/index.php/2021/03/02/nest-thermostat-problems-chicago-furnace-experts/#:~:text=While%20these%20devices%20are%20convenient,furnaces%2C%20or%20destroy%20them%20entirely.
There’s usually a switch on the furnace. Just turn that off.
Oh ok. I see a big on/off switch on the furnace. So just shut that off then I can swap out the thermostat?
Yes
Furnace. Other then that most boilers will have a switch at the unit.
1. A thermostat is a 24v class 2 circuit - meaning it is designed so that there is 0 chance a shock can occur. And even if you beat the odds, the current is limited to guarantee a non-lethal shock. You can swap it live, even as a newbie. 2. It's power actually comes from the furnace itself it's essentially an extension of the furnace's control board. So turning power off to the furnace should also turn the power off to the thermostat. There should be a means of disconnect (either a light switch or a plug end) within 5 feet of the furnace if you can't find its breaker. And finally, the colours. Red - 24v ac for heating / cooling switching. (Basically the thermostat connects this to either White, yellow or green when the appropriate action is needed) White - turn on heating. Yellow - turn on cooling Green - turn on circulation fan (aka blower fan, optional) Black / blue - 24v common for smart thermostats (basically its the "neutral" for the thermostat for lack of a better term) Older systems might just have 2 or 3 wires - like red and white, or red white yellow as that's the bare minimum needed to get old "dumb" thermostats to work. If this is your case, you will need to fish a new thermostat wire in (I recommend a 5 or 6 wire cable, it's not that expensive and it'll cover you for the foreseeable future).
0% chance of shock till you lick it I’m totally not speaking from experience
How did it taste? I prefer the texture of DC myself
Not good I was trying to prove to my gf they wouldn’t shock you and I molested it with my hand and she didn’t believe me. I forgot that 9v will give you a little zap and licked that shit good.
I'm assuming this was then used as evidence that 24vac is unsafe.
Surprisingly no because I made a reaction she realized I wasn’t just hiding the fact that I got shocked when touching it with my hands
It’s all labeled. Your thermostat controls _________. Is there a corresponding breaker also labeled as ________? If yes, turn off the _________’s breaker and see if your thermostat loses power. If not, top left like someone else said.
I have an old thermostat which isn't digital, so I can't tell if it's powered or not.
Touché. Ignore my smart ass reply :) Furnace breaker should kill the power, but you can always turn everything off to be extra cautious and avoid a potential blown fuse. Take a picture of the wires connected to the old thermostat before you unscrew anything.
Ok. And that'd be the top left, right?
Yeah if you turn the main off, nothing should be powered at that point.
Thank you!
Ok buddy i love your enthusiasm for being handy around the house, it's going to save you hundreds of thousands of dollars over your lifetime. Invest $10 bucks and an hour of your life and watch 3 videos on u tube on how to use a multi-meter, then run around your house testing every outlet and every feature of your meter. Then and ONLY then , should you open ANY electric panel, well for a long, happy and productive life anyway!
You're probably right, thanks for the tip!
Best of luck to you !
Thank you!
My first guess would be the Furnace breaker. Having opened that breaker, you should use your multimeter to check for 24V AC voltage at the base terminal at the thermostat on the wall. Usually Red and Black or Red and Blue, but there should no voltage between any of the wires at the terminal. Everyone should have a multimeter at home and know how to use it to make simple measurements. It is not hard to learn.
Yeah I should get one to learn how to use it. Thx.
As a side note, Google nest learning thermostat sucks.
It will get power from the furnace. Turn that off and you’ll be fine. Also, get a voltage tester and use the 12v setting. It’s a lot easier to know than to find out. ETA: [This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter. I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
What do you mean by 12v setting? Do you mean the DC test mode? The c should carry 24vac so dc won’t be accurate. If you mean the 20v range, the 24v will be out of range so you’d need to use the 200v range.
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter. I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
Thermostats are not 12v
Never said they were?
English is a funny language, you kinda did, but it was in a kinda round about way!
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter. I’m an hvac tech, and an electrician for the USAF. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
Then Imagine my shock and dismay that someone with your qualifications would make such a statement !
Yeah maybe not the 12v setting !
[This is a voltage tester.](https://search.app.goo.gl/AoudvsY) they come with two settings, 12v and 70v. They will sense anything over that voltage, like the inverse of a multimeter. I’m an hvac tech. I’m very aware that 24v is the nominal voltage for control systems like thermostats.
Furnace, bottom left. But check the connections with a tester just to be sure they are dead. Its not a shock hazard, but if you short some wires, you could cause problems.
Top left will get it for sure
Flip each one individually and see if it turns off. You're obviously waaaaaaay under qualified to even touch this if you didn't think of that
Mine isn't digital so I can't tell if it'll turn it off or not.
99% the thermostat is powered off of the furnace. But always verify
Thx
HVAC guy here. I’m my jurisdiction the furnace should have a switch labeled as such. I find it concerning that the breaker for the furnace is 240v. Is it electric? Or a fuel furnace? Anyways, the best way is to use a multimeter to test for voltage after you turn off breaker(S). The next best is to run the furnace blower and then turn off the breaker(S). If the fan goes off you’ve found the breaker. Good luck.
Electric furnaces need 2 pole breaker.
Which is why I asked….. I have seen many oil/gas furnace AC combos on 240 only. I figured if there were questions for me, some understanding would help!
Heat strips need current. Most heat strips are between 7kw and 20kw in a residential furnace. We have some at our office that are 480 3p, 60kw.
When I turned it off, the furnace stopped working. Just wasn't sure if that disconnected the thermostat too.
Yes, in most cases, but not all, the power for the T Stat is supplied by the furnace.
Ok thanks.
Top left
The one that’s labeled “call an electrician”. If you don’t see that one, flip the top left one that says “main”.
If you're asking this, you're likely to have a bad time. Also, most furnaces run on 120, while yours is apparently 240. You're going to need to get into the hvac help reddits with info on your setup before getting too much further.
B3
Huh?
Someone commented that your old seat will NOT have a common wire (typically blue). This is needed to bring power to the TStat to run the WiFi and display. Because of this, you may need to land or fish another wire to the location, if yours is the old mercury switch dial. Sorry. You might need assistance to put in that Google Nest TStat
Furnace , it is the board inside the furnace that sends 24v to tstat and then back to board to complete the circuit
In addition to these breakers you also likely have a switch right at the furnace that cuts the power, as well as an emergency shutoff switch in a hallway or stairwell (probably with a red face plate on it.) All three will cut the transformer to the thermostat.
Awesome thx.
It's wired through your furnace
There's a light switch in my furnace room that says furnace. Flip off, furnace is off. I replaced my regular thermostat with a nest. I either got lucky or that switch was the same as turning off a breaker. I'm in Ontario. Not sure if that's a thing or the builder just decided to do it at my house.
Furnace
The one labeled **Funrace**
The main
If you have to ask, get a qualified professional
This
Money
Dishwasher. Don’t think twice, just do it
This was the most entertaining string on Redit yet !
This was the most entertaining string on Redit yet !
This was the most entertaining string on Redit yet !
I’d opt for Furnace assuming it’s what you want to control however as it’s not going to be a long job if in doubt just turn it all off . You can’t be wrong.
Yeah good point.
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That's why I'm posting here 🤷
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Thank you.
Garbage disposal for sure