3rd gen Nest Hot Water on Greenstar 30CDi

[blacklight124]

Hi folks,

Long time lurker here, registering to see if anyone can assist with this. I know there's a lot of flame for Nest-related questions but this is more of a side query.

Ive got my current wiring documented & mapped out. All thats fine. I just want some assistance with the new hot water controls on the 3rd gen.

I have a Greenstar 30CDi combi boiler(http://www.gasboilerforums.com/manuals/worcester/current/greenstar-cdi-installation-manual.pdf)

Now as its hot water on-demand, I dont really need any hot water control (just set it to on permanently) but Id rather connect it if I can, for more control.

Going by page 28 of the above pdf, the only HW related connection appears to be the "Optional frost thermostat connection"

Any help would be grand. Thanks

 

[FurstyFerret]

You have a combi boiler - you don't have any external control over the hot water and when the Nest is installed those terminals will be left empty. During the setup the Nest asks you what kind of hot water setup you have, and you'll pick "Combi".

The frost thermostat has nothing to do with this.

Might be worth paying the extra £40 and having someone from Nest come and install it for you, especially since installing the Nest requires running 240v and 12v in close proximity, and can be unpleasantly fiddly thanks to the backward design and dinky terminals on the Heat Link.

 

[blacklight124]

I can currently turn hot water on/off from the digital programmer on the boiler itself. Thats the kind of control I mean but thats fine if its not intended for normal combi boilers, ive never turned it off before anyway.

Thanks for your concern but im an electrical engineer. I dont intend on installing this "live"

 

[FurstyFerret]

Ah, do you have one of the integrated programmer things installed in the boiler? It uses Worcester's proprietary low voltage control so I imagine you can just unclip it from the panel and the boiler will revert to standard volt free control. At that point the only thing you can do is turn off the hot water pre-heating using the Eco button on the boiler, but the Nest can't do anything from a hot water point of view.

The Nest heat link is a pig to install into existing wiring - it's really designed for smaller diameter cabling IMHO - so if you do have the opportunity to run new cables to it then do so.

 

[blacklight124]

Thanks, yeah Im going to pick up new cabling this weekend. Pulled screws out a blank plate beside the boiler only to discover it was just a hole in the plasterboard with a thoroughly taped up connector block! Fun! This is a flat that's <10 years old too. Cheers for the input

 

[blacklight124]

Interestingly... It looks like I've had "pre-heat" on 24/7 for 7 years.... Ffs

https://www.worcester-bosch.co.uk/s...rogramme-hot-water-times-with-my-combi-boiler

Surely there's a way to program the hot water pre-heat externally then..?

 

[St0rmer66]

Hot water control is just for pre-heat. There is no way to program it without using Worcester's own controls.

The simple solution you seem to be missing is leaving the current timer in-situ and using it to time the pre-heat with the heating set to constant and the Nest interupting this like a normal thermostat would.