Replacing an existing thermostat with the Nest

[Sean Hill]

Hi,

I'm having a look at how to install the Nest (3rd gen) I'm I wanted to have a shot at it myself before calling in a sparky.

I have a boiler (Ideal Classic) in the kitchen together with a programmer. The existing thermostat however I think gets it's supply from the wiring junction up in the airing cupboard upstairs.

From what I've seen, I can wire in the heatlink in place of the programmer, but then the Nest needs a 12v connection to the heatlink.

Or is it possible to install the heatlink near the wiring box in the airing cupboard in order to repurpose the connection to the existing thermostat.

Attaching photos of the kit...

 

[buzzlightyear]

IMO I think you should ring this little chap up .

 

[davesparks]

So youll pay around £200 for a thermostat but not the £60ish to have it fitted safely?

 

[Midwest]

On the face of it, its a simple request for advice. No need to go for the jugular at the first post.

 

[Sean Hill]

Haha, to be fair, I kind of expected it. Although it's not £60ish to fit, cheapest quote I've had is £89. I don't mind paying, just thought I would gauge whether or not it's a simple DIY task when given a little instruction.

 

[shaun1]

I have just installed a nest in my owm house with a very similar wiring set up. Isnthe programmer near the wiring centre? If so you can install the heat link in place of the programmer. You can also install the nest thermostat in place of the existing, and feed it 12v down the exosting cable. However, that cable will more than likely go back to the wiring centre, so you need to get an extra cable from heat link to wiring centre to carry the 12v.

What you will need, is a good understanding of the entire wiring system and a method of testing it, as there are often variations in how each existing set up is wired. I also found it quite dificult to fit all the necessary cables in to the heatlink as the terminals are small. So if you have no experience in these areas I would strongly recomend getting an experienced installer to set it up.

 

[Leesparkykent]

From the looks of it you have a thermal store hence the two pumps. One pump is the pump that is the flow from the boiler and the other is a pump that turns on when the heating is calling. A Thermal store works differently to a normal indirect cylinder....The boiler would normally maintain the temp of the thermal store and when the heating is calling the heating pump would turn on causing a flow from the cylinder. Hot water will be at mains pressure as the cold goes through the coil/heat exchanger in the store and comes out the other end of the coil hot as it’s heated by the hot water in the store. It basically works in reverse to a indirect cylinder. You would normally maintain the temp of the thermal store so you have HW on demand and when heating is required it can draw straight away.
I would be careful in who you get in to install the nest as they will have to know what they’re up to to change the settings etc.