How long have you lived there? If you recently purchased/moved-in was it flagged in the home inspection and/or can the previous owners shed light on how it works? If not, suggest you contact a reputable HVAC provider in your area... Hopefully a simple fix...

These are old Honeywell thermostats. Honeywell is not going to be able to tell you how the thermostats are connected in your house. You need to hire an HVAC tech to trace the wiring of each thermostat and determine how they are connected to your heating system. Do you also have an AC? The top thermostat has a heat and cool switch. The round thermostat is for heating only.

Recently purchased home. Thermostat was not flagged by inspector. It was working fine as far as we could tell when he checked it.

I'm pretty sure there's just heating so I guess the "cool" switch doesn't do anything?

The other thing is, we're doing some remodeling right now and have disconnected one of those temperature dialers. Would that affect the HVAC system?

You are not sure if the house has AC? Disconnecting one the thermostats is going to affect the HVAC system. To what extent is not known until you trace the wiring.

I'd call in a licensed HVAC pro. Call it a maintenance visit, during which they can check what you have, make sure it's operating properly and safely, and explain to you what you have and how it works. And to give you options too, if that's what you want. Let them know in advance what you're looking for so that the right person is sent to your home.

Is there a way this system would typically be wired up?

The three thermostats would typically be connected a zone control board. The board would be wired to dampers and the furnace. The dampers would open or close depending on what zone is calling for heat.

A house I bought had two thermostats. I spent a little bit of time trying to figure out which did what and couldn't figure out. Had a "maintenance" visit from an HVAC service company, who determined that one of the thermostats wasn't connected to anything. He speculated what happened was that a prior owner had decided to relocate where the working stat would be and simply kept the old one in place. It was hard to see what was happening because the dummy had wires connected both at the stat and on the furnace - it turned out whoever did the work cut the wires in the attic.

I have a T8085 thermostat. It won’t turn off. Power went out and when it came back on, so did the unit but it was not on when the power went out. Timer hasn’t been set in years. Not even sure if it works. I don’t have any of the pins to set it. The switch is off but unit runs. Fans is set to auto and heat is off.

How do I get it to turn off!