Honeywell Focus Pro 5000 Home Heat Thermostat Problem ?

Assuming you've ruled out any possibility of human involvement, then yes, I'd say it's defective, would not trust it, and would replace it ASAP. And until it's replaced, I'd keep an eye on it, turn it off if you're away from the house, etc.

I have experience with a couple of Honeywell VisionPros and highly recommend them. The only downside is that HW won't talk to you for help in anything to do with setting them up, setting the programming options, etc. They want you to call a guy with his butt crack showing to come for a visit.

If I were buying a new thermostat I'd want one that has wireless internet connectivity. Main feature there that I'd like is the ability to get the thing going when you're on your way back after having it set back. Example would be going on vacation or even a local trip when you're not sure when you'll be back.

Did you check the program? Maybe it mistakenly got set to turn the temp up to 85. You could also try a full factory reset. Even if that is the case and a full reset fixes it, I would still think about replacing it unless you are sure you somehow caused the problem.

Oops. My previous post assumed it was programmable, but it look like it isn't. I would still check for a reset function and try that - or just buy a new one.

Hi, I'd give it one more chance to see it acts up again. If it happens again, time to replace.

Hi, Right. If it were programmable, most programmable 'stats can be tested in service mode. I am wondering if there was power spike or some thing like that in the house yesterday.