Help with thermostat installation! Furnace is on roof!

So… I’m at the part of the thermostat installation where it says “Go to your furnace and open your system’s cover”. I have a cooling/heating unit that is on my roof. I cannot climb up on my two-story house to have access to my cooling/heating unit. Is that what the instructions want me to access? That large unit on my roof? If so, I guess I’m returning my thermostat.

I’ve installed programable thermostats before, but I’ve never had to do anything to the furnace, just installation at the wall.

Please help me understand.

Thanks, Debbie

Do you have an air handler indoors, or just a package unit on the roof? How do you change the furnace filters if you cant access your furnace?

Thank you for replying.

I don’t know what an “air handler” is. I change my filters in my upstairs hallway ceiling.

So a package unit then. If you do not have a common wire at your thermostat then you would need to either go up on the roof to install it or have someone else do it for you, or return the wyze.

Here is my thermostat configuration. How would I know if I have a ‘common wire’?

You could try uncoiling that blue wire there and see if your installer attached it to common by putting it in the C terminal of your wyze and putting the red wire into the Rc terminal. If your wyze lights up, then you have a common. Otherwise someone needs to go on the roof and attach the other end of that blue wire to the C terminal on the package unit.

Thanks. I guess that would be worth a try before returning it.

Highly doubted any tech would connect C at furnace side and leave unconnected at Tstat.

Heat raise up and if your furnace is on roof top, not sure how efficient it is in 20F.

I’m in Las Vegas. Our low temps are in the 30sF, and not very often. I come from CA, and most of the places I lived in CA also had units on roof. Sometimes on the side yard, or backyard, too, though.

I do have an unconnected wire on my thermostat. I figured it was a ground wire that wasn’t connected. I’ve put it all back together, now, with the previous programmable thermostat… but I think it was a brown wire.

I connected the wires in every configuration that looked like a possibility, but never got the “WYZE” to light up. :frowning:

Thanks for the suggestion, though.

There were some informative websites. This website < The C-Wire Issue – And How to Solve the Problem > offered a solution to getting a “C” wire, but two options still had me going to the furnace, with is my initial problem: no access (because of the roof mount.) The third option was an external transformer, which is more possible than me going on the roof.

I’ll contact WYZE this week and see what they say. I’m sure I will not be the only one with this issue.

If you use an external transformer, the wyze will only control your heat, not your A/C. The easiest way in your situation would be to ask a friend who’s good at working with electricity and isn’t afraid of heights if they can go onto your roof and connect the blue wire coming out of the thermostat bundle to the C terminal. A HVAC company will probably want to charge you $100 or so to do it, but a friend will likely do it for a few beers :slight_smile:

Remind me a few year ago, My neighbor sent his wife up the roof (3 story high) and he is not good with height. He was holding the 32 ft ladder.

Debbie I too am in Las Vegas and am having a hell of a time to get my Wyze Thermostat installed. I have two systems in my house. One AC / Heater for upstairs and one for downstairs. There are also two thermostats as well.

While I can get everything connected and the Wyze unit to power on the moment the heater kicks on there seems to be some sort of power issue and the unit turns off.

I have the same wire setup as you. Did you ever get the dam thing to work?

Show images of furnace board and thermostat wiring along with previous thermostat wiring if you have it.

Hi Debbie,

I wish the “C” wire had never been renamed. It confuses what is actually very simple. “Normal” thermostats have no ground wire. They are simply a switch that always has a “hot” wire in and when they want call for heat (or cool), they connect the input hot wire to the driven output hot wire. They are run their display by batteries instead of electricity from the system. You need a DC ground wire – it does not even have to be connected to your system, but in a new system that’s an easy place to get it. There are simple cheap plug in devices that serve this purpose. They vary a little for different thermostats. I’ll give you an Amazon link to mine ($11) and you can get a similar one for your thermostat. My link is:

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C is Common. In simplest terms, it’s like neutral on your wall outlet, It’s just the other side of the wire that goes through the transformer to make R. The voltage between C and R is generally between 25 and 30 VAC, and all things that are controlled by 24v logic in your furnace/air handler/ ac are constantly connected to the C side of the transformer.
When your thermostat wants to turn one of them on, it just switches R to that component, and that allows current to flow through that component.

Well… thank you for all of your suggestions. I contacted Wyze today for a return/refund. I’ll stick with my programmable thermostat for now. Just too many installation headaches for me with my unit being on the roof. I’m not going to pay someone to go up there and my HOA maintains the roof, so they don’t want you walking on it (it’s tile). The external transformer alternative looked like a possibility (I have an outlet on the backside of the thermostat wall), but with @speadie 's comment “If you use an external transformer, the wyze will only control your heat, not your A/C.” …well, that’s just not going to work in Las Vegas. :smiley:

Good luck @opstech with your set up. Let me know if you work something out. I’m out for now.

Looking forward to the doorbell arriving in February. Planning on having better luck with that.

Happy new year!


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The reason you need common wires on Wyze is it’s WIFI transmitter requires constant power that a battery can’t supply.