Hi,
I have a hydronic heating system that uses two 120 Volt thermostats in 2 zones. The thermostats turn the circulator motors on and off. I replaced the old manual Honeywell thermostats 10 years ago, at the recommendation of the local plumbing supply, with programmable set back thermostats also made by Honeywell (Honeywell Chronotherm). I am considering replacing the current ones because the house warms up about 5 degrees warmer than the set temperature before turning off the heat and cools down about 4 degrees cooler than the set temp before turning back on. I would like a set up that is more precise.

Is there a way to adjust these thermostats for more precise operation?
If not, can anyone suggest an alternative thermostat?
Are low voltage thermostats more precise? If so what is involved in rewiring for low voltage.
Thanks,
FBANP

That is quite an operating span.

Stay with line voltage stats, re-wiring to low voltage stats would require transformers and relays with LV stats to continue to operate line voltage devices.

Check to see if the new stats can be calibrated so the on and off is closer to one degree above and below the desired setting.

My stats actually have a calibration you can set for that exact problem. Are you sure yours don't?

Thanks for the responses.
I do not have the original manual that came with the thermostats. Nothing externally or under the faceplate appears adjustable.
I guess I could check with Honeywell.
Thanks,
FBANP