I’ve got a new ct100 plus that I installed back in October, running @RBoy 's enhanced thermostat DH version v04.00.00 . It’s been working great, up until A/C season started. There’s nothing wrong with it responding to commands, but it seems that the temperature reading does not necessarily reflect when the room is cooling down, causing the A/C to keep running for extended periods of time.
Tonight, we came home around 7:15, the house was 77F, and the thermostat gets set to 76F on returning. WIthin the first ~10 minutes, the thermostat is reading 76.5F. Two hours later, the A/C is still running, and the living room (next room from the thermostat) is down to 74F, the master bedroom is down to 72.5F, and the thermostat is still reading 76.5F.
So I know the air is cooling around the house, well past the cool setpoint, but it’s like the thermostat doesn’t want to get the drift and recognize that fact.
just a guess, maybe you haven’t operated it in a high-demand cooling mode until now. Maybe there is a heat source on the tstat location, acting in summer, that does not act in winter. Possibly even in the wall - you could insulate the hole.
Reminds me of the time that I got frozen on an intermittent basis in winter in a datacenter office, it seemed mysterious. In that case, a laser printer vent was hitting the tstat from 6-7 feet away and was sorta channeled to it, but only when printing - sneaky.
The tstat could be failing or miswired for cooling, or the HVAC controller could be failing. When my furnace was troubled, it would run-on for hours, even though actual heat was correctly cycling and on average, it was able to maintain temperature. Looking at the controller, it did flash a code, in my case 5-fast-blinks, indicating “flame without ignition”, which was actually untrue, but the run-on condition is both a fail-safe response and a notification to “look at the HVAC, dummy”.
I finally replaced the controller after 2-3 years when it ran for 8+ hours straight. Saving that fan energy.