Good day all,

I may well be late to this party ,but just in case.

A Nest has been my heating thermostat for about 3 years. Over that time i’d noticed that the boiler would fire at times for no reason. Lots of checking of wiring etc, never solved it and as it was seemingly intermittent ( and over heating season went unnoticed) however last few weeks i seemed to notice it most days.
A bit of online enquiry, throws up that nest has a built in Legionella feature, it will fire the boiler and run the hot water circuit if water hasn’t been heated for an uninterrupted 2hour period in the last 48 hours.
Plus my boiler is unable to have seperate flow temps for hot water priority or heating and so i set it at 55 , unless it’s below zero when it gets increased. ( despite being opentherm compatible, i’ve never managed to get it to work with the nest) Boilers a Baxi system.
Absurd when my tank needs less than an hour to recharge and i’ve got the water programme set accordingly. Plus the Nest can’t read either the boiler flow temp or tank temp, so relies on the boiler being set high enough along with the tank to achieve its aim.
So out of heating season it would seem i’ve had the boiler running most days for 2 hours for no reason.
The Bacteria control setting can’t be accessed in the App only through the stat itself.
Seems a rather pointless feature and one which should be flagged more prominently.
Remains to be seen how much effect it has on my gas use.

In hindsight and being a bit more informed , i’d have chosen a better boiler and made sure my controls were definitely supported, really can’t see that i’d recoup the cost of changing them in additional energy savings, so i’ll be just keeping an eye on things a bit more closely and see what happens.