Nest 3rd Gen works... Somtimes (Due-tec Combi)

[houserandall]

Ive searched quite a bit for this problem but cant find anyone else having a similar experience. Installed a 3rd Gen Nest on a Due-tec Combi HE a Range boiler. It had no existing thermostat on it. It was controlled by a Multifit Integral 24 Hour Electro-Mechanical timer.

Everything works great, no problems installing it, no problems with anything. I can turn the boiler on and off from the home wifi and away from the house. The problem starts after I leave it for a day. When i come back to turning the boiler on it wont turn on. I can hear the Nest link clicking as if its trying but the boiler isnt coming on. If I turn the boiler on via the Timer we are up and running again and everything works.

I've tried turning the timer to manual and deleting its existing timer settings thinking its clashing with the Nest, still not working.

I thought maybe the hot water is the problem, having a shower on the morning seems to be the only activity that the boiler sees. Doesn't make a difference. Ive tried the hot water multiple times and Nest works. I cant be sure but it just doesn't want to work after about 12 hours.

I've included all my wiring in the images below along with the boiler diagrams. I feel its something to do with the existing timer cutting the power to the nest but cant be sure.

Anyone had similar problems and have any suggestions?

Dropbox - Boiler - Simplify your life - https://www.dropbox.com/sh/duzrs7rhn3qk59g/AADltsW4I_veMqXKmmpInMuBa?dl=0

Thanks
Gav

 

[buzzlightyear]

Are you a spark ?

 

[houserandall]

I'm not, my father who installed it was but has been retired for the last 10 plus years. He says its the first nest he has installed but isnt any different from a typical thermostat. We have been in touch with nest but they are pretty useless and over the phone you can't really blame them. Obviously the next step is a nest specialist to come out and take a look but i thought id try here in case it was something obvious that was overlooked.

Its also quite tricky to show someone when you cant repeat the process thats knocking it off. Maybe taking out the Multifit timer is worth a try and seeing if thats the problem.

Cheers

 

[Midwest]

I have no experience with Smart Stats, but I'm suffering myself with a extra low voltage sensor and induced voltages. I understand your not a sparks, but I'm led to believe the Nest uses extra low voltages. Just a thought.

 

[Sparkie30]

You have wired wrong on the boiler. Need to swap black and grey.

Black is permanet to terminal 2 on nest from 230v live out.

Grey on (on 3) your nest is switch line so it goes where is says switched live in.


Good luck.

 

[Sparkie30]

I have no experience with Smart Stats, but I'm suffering myself with a extra low voltage sensor and induced voltages. I understand your not a sparks, but I'm led to believe the Nest uses extra low voltages. Just a thought.

Nest uses 230 to do the switching but the stat requires a 12v dc to operate.

Easy to install and operate to be honest.

 

[houserandall]

You have wired wrong on the boiler. Need to swap black and grey.

Black is permanet to terminal 2 on nest from 230v live out.

Grey on (on 3) your nest is switch line so it goes where is says switched live in.


Good luck.

Think this has done it. Your a true star. Really appreciate it!

 

[houserandall]

Actually sorry I tell a lie. That hasn't fixed the problem. This morning trying to turn the nest on via the app and termostate. They both say its on and you can here the link clicking but the boiler didn't turn on.

Still have to press the on button via the timer on the boiler.

 

[123]

Set the timer on the boiler to be permanently on and just use the Nest to control your heating. At present both the timer and the Nest will need to be on for your heating to come on.