Replacement Thermostat Question

mgambuzza

I currently have a "newer" Honeywell round thermostat that I believe has issues. The switches are set properly. For example, with the room temperature showing about 66 degrees, I have to set the thermostat between 72-74 in order to turn on the boiler. If I try to reduce it to 70, as soon as it goes below the 72-74 range it kicks off. If I keep it at 72-74,it will run and maybe bring the system up to 68-70. If I set the temperature to 78 and it brings the system up to around 72.

In a replacement, I was going to see if a could find a new old stock Honeywell T86A (merc), or something similar to get better/more accurate performance. I had to search for a vintage style thermostat a few years ago at my old house to control my pellet stove as newer ones didn't seem to have a good enough "closure" to simulate a short circuit, allowing it to fire up.

Ironman

Make and model of boiler? How many wires in the thermostat cable?

Jamie Hall

Is this a CT87? If so, having it level is critical. Is it?

mgambuzza

Ironman said:

Make and model of boiler? How many wires in the thermostat cable?

Utica PEG300CDE, 2 wire.

mgambuzza

Jamie Hall said:

Is this a CT87? If so, having it level is cri
tical. Is it?

Current one is a Honeywell T87K1007. Yes it is level, and set for Steam/Gravity.

Ironman

That’s not a very reliable one. It’s a power stealing model that’s used when they’re only two wires available. You may have better results with a new one.