Replace British Gas UP2 Programmer with Nest 3rd Gen

[silversurfer79]

Hi guys, like the subject suggests I try to replace my by up2 with a nest 3rd gen thermostat. My up2 controls both the hot water and heating and the nest can do both. The issue I have is the up2 has two calls, one for HW and the other CH and they seem to share a common. See picture 1. The Nest though seems to need commons, one for the HW and CH, in not sure what to do about this now. Can I split the common for the Nest, only connect one common and the Nest internally will share the common or would i need to add an addtional cable from the boiler? The boiler is a Potterton Precision if that helps.

 

[Aquaheat]

Here we go again!

 

[Aquaheat]

OP, everything you need to know is in the very simplistic wiring diagrams that come with it and can be found on line.

 

[silversurfer79]

That's not helpful, I've read the Nest manual and the boiler mammal and the programmer mammal more times than I care to admit. I'm not sure where to get the extra common from or if I can split the single common that I do have. I've mail Nest and they won't advise besides that I need two commons, but I don't know where to get the 2nd from.

 

[Aquaheat]

It clearly shows you in the diagram.

Spend more time on the manual and less on the mammals.

Jon

 

[Aquaheat]

As said all the info you need is right there in the manual.

When you've finished with the mammals you can thank me later

Jon

 

[Steelmasons]

Earth core being used as a switched live boils my pizz... @ least they used a SL to close HW port....something I suppose.

 

[Aquaheat]

Couldn't even stretch to a bit of heat shrink and mark it up properly!

 

[Steelmasons]

Couldn't even stretch to a bit of heat shrink and mark it up properly!

More than likely a sparkie wired it as us heating guys wouldn't do that..

 

[Echo the husky]

It's one of the better installed heating wiring from what has been shown recently! Though we can only see one small part of the install... I wouldn't use g/y for anything other than earth but it is permitted if it is properly identified at all terminations.

OP you have a Y plan system, the wiring diagram clearly shows you how to connect each wire. Just to help you further:
Brown wire is Live supply
Blue wire is Neutral
Green and yellow (which needs a brown sleeve) is HW off
Grey (which needs a brown sleeve) is HW on
Black (which needs a brown sleeve) is CH on

You will need to alter your existing room thermostat wiring if one is fitted, which is also explained in the manual.

 

[Aquaheat]

Cough Cough never!!

For a start there's no copper showing so it wasn't me!!

Jon

 

[silversurfer79]

Any suggestions? The heating is done by a combi and the hw is from a hot water tank. I've just bought the house and still trunking piece this together.

 

[Steelmasons]

OP you have a Y plan system

Could be a MOMO valve used for hot water zone.....do not assume....

 

[Aquaheat]

Jesus this is painful. Ok keep this under your hat @silversurfer79 I just want a quiet night.

Edited till the post above is clarified. If we can't get a boiler type right I'm not helping with the wiring!

Jon

 

[Aquaheat]

Any suggestions? The heating is done by a combi and the hw is from a hot water tank. I've just bought the house and still trunking piece this together.

Chances are its not!! Whats the boiler make and model?