Help with Nest install

[ro13erts]

Hi,

I have a Worcester Greenstar 38 CDi, with a Danfoss TP5000Si programmable thermostat. I want to replace this with the Nest setup. The nest heatlink wiring diagram has three inputs (satisfied [optional], common, call-for-heat) and the current Danfoss setup has three inputs (N/C, Com and N/O). Only the Com and N/O are connected.

These are actually the same thing with slightly different names right? So, as long as i source a separate power source to power the heatlink, then I just connect the above two wires up the same as the Danfoss?

If it's any more complicated than that, then I think I'd better seek a pro , but I don't want them to come out, connect two wires and looks at me like an idiot!

Many thanks in advance!

 

[jackthom]

Yes it is that simple. On the Nest Heatlink, terminal 2 is Com (Common) and terminal 3 is the same as N/O (Normally Open ie call-for-heat.)

The heatlink also needs "permanent" Live And Neutral supplies, ie from the same mains feed as the rest of the boiler system.

 

[ro13erts]

Brilliant news, thanks for your time.

 

[Danny Slinn]

Hey guys

Saw what you did a few years ago and wonder if you could help me...

I have a two zone system. See pictures of boiler, at the zone terminals and at both thermostats.

How can I install the wiring for nest? Hoping to have 3rd gen and 2nd gen on a zone each. Providing power to it on my wall near the front entrance. Or is it possible to have just one nest and it work the entire house, eliminating the zones?

Please let me know if anyone can help me set it up!

Danny

 

[stem]

Hi Danny and welcome to the forum.

Probably no one has replied before, because your message is hidden at the bottom of an old thread and nor readily seen. This is known as 'hijacking' and is actually against the forum rules. You should really have started your own new thread. Don't do it now though, or you will be starting a duplicate thread, which is also against the rules.

Anyway back to your question. The wiring centre labeling in the lid has been ignored by the original installer, so doesn't represent what you actually have. So don't take too much notice of it.

Also, as you only have two motorised valves connected I assume they are for Zone 1 & Zone 2, meaning that you have a combi boiler supplying hot water and don't have a hot water cylinder somewhere.

The black wire with brown sleeve, and brown wire going to each of the existing room thermostats need re-directing to the appropriate Nest Heatlink terminals. There isn't a neutral present at either thermostat now, so you will need to add one.

I have drawn a diagram of Zone 1 below. [Zone 2 will be an exact copy]



If it's easier for you to install the Heatlinks near the wiring centre, the cables presently going to the thermostats are connected to the wiring centre as follows: The brown wires are connected to the live terminal (top horizontal terminal, with the grey wires in the other side) and the black with the brown sleeves are connected to wiring centre terminals (6) and (10), but you will have to follow the wires to the motorised valves to find out which is Zone 1 and which is Zone 2.

Then remove the existing thermostat wires and run new ones in their place to the Heatlinks. You can pick up the neutral from the wiring centre (N) terminal.

 

[Danny Slinn]

Thank you so much for your help.

I am new to this forum stuff so I didn’t know the rules! Apologies everyone!

Anyway, I will give it a try and report back.

Your help is very valuable, thanks!

Danny

QUOTE="stem, post: 4062991, member: 20409"]Hi Danny and welcome to the forum.

Probably no one has replied before, because your message is hidden at the bottom of an old thread and nor readily seen. This is known as 'hijacking' and is actually against the forum rules. You should really have started your own new thread. Don't do it now though, or you will be starting a duplicate thread, which is also against the rules.

Anyway back to your question. The wiring centre labeling in the lid has been ignored by the original installer, so doesn't represent what you actually have. So don't take too much notice of it.

Also, as you only have two motorised valves connected I assume they are for Zone 1 & Zone 2, meaning that you have a combi boiler supplying hot water and don't have a hot water cylinder somewhere.

The black wire with brown sleeve, and brown wire going to each of the existing room thermostats need re-directing to the appropriate Nest Heatlink terminals. There isn't a neutral present at either thermostat now, so you will need to add one.

I have drawn a diagram of Zone 1 below. [Zone 2 will be an exact copy]

View attachment 133700

If it's easier for you to install the Heatlinks near the wiring centre, the cables presently going to the thermostats are connected to the wiring centre as follows: The brown wires are connected to the live terminal (top horizontal terminal, with the grey wires in the other side) and the black with the brown sleeves are connected to wiring centre terminals (6) and (10), but you will have to follow the wires to the motorised valves to find out which is Zone 1 and which is Zone 2.

Then remove the existing thermostat wires and run new ones in their place to the Heatlinks. You can pick up the neutral from the wiring centre (N) terminal.

View attachment 133704[/QUOTE]