Installing a Nest 3rd Generation on a Saunier Duval F30E SB

[christo2012]

Hi,

I have recently bought a new Nest with a stand and having previously installed a Second Gen on my old boiler, thought that this one would be a doddle too! How wrong I was. We have just moved in to our new home and the new baby is due any day!! The system is a Saunier Duval Themaclassic F30E SB.

I wonder if someone might be able to point me in the right direction as to how to wire it in. Have seen another post on here about a Saunier Duval but about a combi boiler. Mine is a system boiler. The heating and hot water both work fine running off the old programmer, but would prefer to have it running off the Nest

Thank you from a very cold Edinburgh! Any help would be much appreciated.

[chrrris]

I have recently bought a new Nest with a stand and having previously installed a Second Gen on my old boiler, thought that this one would be a doddle too! How wrong I was. We have just moved in to our new home and the new baby is due any day!! The system is a Saunier Duval Themaclassic F30E SB.

Heheh... there seems to be a run on people posting here about the Nest recently for some reason.

As you've found - there's a big difference between installing a Nest to do heating-only on a combi boiler (usually fairly easy), and installing with a system boiler to do CH and HW. Your make/model of boiler isn't really relevant in this instance. What you need to do is have a read up (google/youtube/etc) about the different types of heating system in the UK (S plan, Y plan, W plan, etc) and establish which type you have. Then find the wiring centre for your boiler and do a little diagram of what currently goes where (this should make some sort of sense to you when you understand how the different systems work).

The Nest comes with an installation booklet with diagrams for all common types of setup, so once you know what system you have, you can find the right diagram and, basically, implement that.

I don't mean to sound like a complete ar$e, but there's no easy "connect the blue wire to terminal A, connect the yellow wire to terminal B" style solution and some wiring centres can be a real rat's nest of cables on first glance... it should all make a lot more sense once you understand what system you have at the moment and how it works.

Hope that helps a bit, anyway.

[christo2012]

Chrrris,

Thank you for your response. Was hoping that you would reply as your replies usually resolve people's issues!
I think it's a Y system as only one valve. I will investigate further and let you know. There is an old programmer running the show at the moment. Ideally I will just disconnect that and let the heat link do the work!

[chrrris]

Sounds like Y plan, yes. In an ideal world, the wiring centre would look like this:-

although, they never look quite as easy to follow in the flesh with wires going all over the shop Also the terminals used for each thing are often different, or you have 2 or 3 different smaller block connectors (not always in the same box) rather than a single one with 8 or 10 pairs of terminals, which makes it look a bit more confusing.

Page 25 of the Nest booklet has the schematic showing what needs to connect to what for Y plan, but you'll need to verify the actual terminals in your own wiring centre. 1,2 and 3 are usually Live, Neutral and Earth but everything else can be a bit of a free-for-all. Make a diagram or, if you can get a decent photo, take a pic before you start -- then you can at least put it back how it was if it gets messy

[thescruff]

Have I gone doolally or is that drawing wrong. Looking at the cylinder stat and the writing above

[chrrris]

Have I gone doolally or is that drawing wrong. Looking at the cylinder stat and the writing above

Hahah! Yes, I do believe you are right (common and HW on are labelled/drawn the wrong around, yes?). That'll learn me for googling "Y plan wiring diagram" and just linking to the 1st image I found

EDIT: Hang on, no - on second thoughts it looks okay to me actually??

[christo2012]

Lucky that you both spotted it!!

[thescruff]

Had to go check This is the standard Honeywell drawing although I think maybe the other one will work, need to give it some more thought.

Edit. in the htg only mode theres no power to the grey so the valve wouldn't move right over

[chrrris]

Edit. in the htg only mode theres no power to the grey so the valve wouldn't move right over

I had to sleep on it, but, yes - I think you're absolutely spot on there.

Just goes to show how awkward it can be sometimes -- somebody sat down in front of a computer to draw that schematic and still managed to get it wrong. Trying to do it in a cramped, dimly lit, spider infested cupboard in someone's house is even harder