Honeywell CMT927 wireless stat

I have several CM927s in installations I've done and, although none gets power cycled frequently AFAIK, I've never had this issue. Sounds like a bad 'un.

I agree it sounds bad but I've had it on another install too.

The common feature in both is that for a period the systems were subject to repeated switchings on and off via a switched FCU so I wonder if there was something inductive (like a boiler LV supply transformer) kicking back on switching off and causing corruption of the EEPROM data in the relay box. Not something I would expect from a Honeywell but who knows, maybe time for a suppressor at the relay box.

On the current one I went back today and did a factory reset on the wireless box and a re-binding to the relay unit and all appears well. The other was an isolated occurrence but it hasn't been power cycled since.

The installs were a year apart so I'm not suspecting a batch problem.

I know a few have them here but none have reported problems.

Thanks for the feedback.

I don't know this one, but could it be a battery died somewhere, either in the remote, or backup battery to handle mains outages?

In article , Andrew Gabriel writes

It's _the_ Honeywell 7 day programmable wireless stat.

The wireless stat batteries are good and following a factory reset and re-binding of stat to relay unit so it does imply some kind of corruption.

They claim, "EEPROM memory holds the user program indefinitely" but I can see that may be the wireless unit only and perhaps they have gone the dirty way of a battery in the relay unit which I suspect would be more susceptible to corruption than EEPROM. I would be surprised though, little EEPROMs are dirt cheap.

Now that's it working again I'm forbidden to dismantle anything to take a look, next time I'll pop open the relay box and report the findings.

Well thank you, too: I'll watch out for it on the ones I've put in.