Nest 3rd gen default to hot water on.

[RayPlumb]

Just had a problematic install of a nest 3rd gen. System is s S plan, wiring was a bit fiddly but got it done. Switched it all on and hot water cam on. Checked nest thermostat and hot water is set to off. Rechecked all working again and narrowed it down to heat link constantly calling for hot water. Phoned nest 30 min later after tech guy spoke to a few others. The thermostat has an antibacterial mode that switches water on if dormant.. presume also at inital start up. Can be disabled. Nest said it is a software issue they are looking in to.. 3hrs later. This is all new to me so thought i would post if anyone else having this problem..

 

[mgw]

Thank you for the post, yes also having problems with DHW switching on when not programmed, if I turn off the schedule then it does not heat the DHW, and with schedule set 7 days a week it works OK, but set to 4 days a week, and on the days it should be off, it randomly switches on.

 

[RayPlumb]

Thank you for the post, yes also having problems with DHW switching on when not programmed, if I turn off the schedule then it does not heat the DHW, and with schedule set 7 days a week it works OK, but set to 4 days a week, and on the days it should be off, it randomly switches on.

In the menu there is a legonellas bacteria protecion option. You need to disable this if you done what that to switch on.

 

[mgw]

In the menu there is a legonellas bacteria protecion option. You need to disable this if you done what that to switch on.

Thanks now disabled to test, not sure if I want to leave disabled or not? However I do want to prove that was why the boiler was firing up.

 

[mgw]

Yes it worked, now no random run of boiler, seems Nest is not only controller with this feature, however some other system only do it once a week, not every 48 hours, so maybe better to program a 3 hour run once a week rather than have a random time selected by boiler.