r/thermostats

I upgraded us to a new Smart Thermostat February 2026. The Honeywell RTH9585WF Smart Color Thermostat.

Our home is old enough that we don't have a C wire, so I used the included wire for a bridge. Furnace worked great for months. Summer rolled around and the air conditioner worked great for months.

Suddenly (in 100 degree weather no less) the thermostat quits working. When I go to use the app I have an alert that it's lost connectivity. Thermostat itself is dead in the water. Blank screen.

I had a new one in the same model so I figured I would try that. It powered on, I got it all synced with the app, we're in business again. Fast forward 8 hours, and I have another dead thermostat.

What do I need to check/photograph/look at/or test to figure out what is causing this?

https://preview.redd.it/wqdc284eskbh1.jpg?width=3024&format=pjpg&auto=webp&s=d7aaf1ba8442365745df4f5db91afe67cc673414

Hey, I installed a Nest thermostat yesterday and it was working fine other than not being able to connect to the app due to "low battery" Well i woke up at 5am and the house is at 30°c. The Nest said cooling on the display but full heat was coming out of the vents. Lucky I still had my old thermostat, I re installed it for now and am getting cold air. Anyone ever have this issue before? Thanks

We recently had to install a new system so we went with a two stage daikon as we live in sw Florida it has been much more comfortable. We have a 3rd gen nest from that we've been using since our apartment. We had new wiring ran so it is using the full two stages okay but I have been seeing that they are not optimal for these types of systems. So let's say that money isn't an issue (right lol) what would be the absolute best thermostat to run this set up?

This is my system for reference
DAIKIN 17.2 SEER2 A2L TWO-STAGE CONDENSER
/ VARIABLE-SPEED AIR HANDLER DC7TCA4810A/DMVT48CP1300A

Background- My church has tasked me with replacing four thermostats in different areas with smart thermostats after receiving a green grant.

Me- I'm the smartest tech guy at the church. Which isn't saying much. But I can connect to the Internet and run an anti-virus, so I'm a pro according to some folks.

The dilemma- Two, maybe three of the rooms will need remote sensors. We currently have remote sensors connected to our Honeywell programable thermostats (which also have C wires). However the smart thermostats with remote sensors also have a lot of bells and whistles that we don't need, and a price that reflects that.

Questions- Is it true that I can't use my existing remote (wired) sensors with a smart thermostat?

And are there any basic smart thermostats you all would recommend that also work with/or include the sensor?

I have a Neat thermostat, the older learning thermostat 3rd gen. Setting it up in HA was a real pain. It's working now and I do worry about the API one day not being available. I realize T6 is local and faster response. Would I be gaining and/or losing much with this swap?

My current thermostat is battery operated. I bought an ecobee but realized that I can’t use it because I have no C wire. I’m renting and the furnace is in the ceiling I can’t access it, so I can’t install an adapter either. Basically back to square one.

I want a smart thermostat but not sure if a battery operated version exists that doesn’t burn through batteries.

Any suggestions on the best way to upgrade?

Looking for feature comparisons between these two brands/models specifically (and ecobee) for a small ranch home. I know Google is within the Axis of Evil. Why these two? Nest Learning 3rd gen because I already own one for my apartment. Honeywell X85/X2S because USAA offers Home Insurance discounts for them, and GA Power offers them cheap....also ecobee Enhanced and ecobee Premium.

1,500 sq ft ranch home. Large Southern city. Heating is electric. Single human occupant. Eventually would like to link everything in Home Assistant, although somewhat invested in the Unifi ecosystem currently (router, switches, WiFi).