Simple DIY Nest Installation in the UK

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Yesterday I bought a Nest Learning Thermostat to replace an old programmer at home. I checked with local certified installers and was amazed at the cost of installation. The cheapest quote I received was £120. So, I decided to at least consider trying the installation myself...

Before I start I should stress that our heating setup is relatively simple and that if you have any doubts whatsoever, call in the professionals. So, on to that heating setup. We simply have an aging Baxi 105e combi boiler and a programmer linked directly to it. We didnt have an existing thermostat or extra peripherals such as a pipe stat or frost stat, and no junction box. Based on the simplicity of this setup and prior posts found here and elsewhere I decided to give it a go. I went for the low voltage setup (as described in the nest installation guide and set out below) as this appeared the clearest and simplest option.

The first thing I did was to check the connections on my boiler. These were actually pretty simple. I had a live wire (brown) at the leftmost side (next to the fuse), followed by a neutral wire (blue) in the next position, and a yellow/green earth wire at the next position. These provide the mains electricity supply to my boiler, and are all tied up together in a single grey cable that enters the boiler from outside. On the other side of the terminal block (if we describe the connections I just outlined as supply) I had the same coloured cables running out to the rest of the boiler. Hence, it was pretty simple to see that this was the mains supply setup. I then had two further cables connected at the last two remaining 'supply' side points on the terminal box. These were the connections from my existing programmer (there was also an earth cable from the programmer to the earth point (third along from the left)). So overall the terminal box was laid out as (from left; side with the amp) Live; brown mains supply, Neutral; blue mains supply, Earth; green/yellow mains supply and green/yellow programmer earth, remaining positions 1 and 2; remaining programmer connections.

As we always use hot water on demand (happy to wait 30 seconds for hit water), our programmer was only really necessary for setting our hearing schedule. As Nest takes over this role, I decided to disconnect my current programmer entirely. So, having disconnected all power to the entire house to ensure I couldn't kill myself, I removed the programmer's connections from the boiler terminal box at the earth and points 1 and 2. I capped the cables to secure them and tidied them away. This left only the Live, Neutral and Earth cables from the mains running to the leftmost 3 ports on the terminal box.

Next, I set about wiring up the heatlink. The heatlink does not require its own earth cable, so in terms of providing it with power, only the Live and Neutral were necessary. I connected up the L port on the heatlink to the Live port on the boiler terminal box (nearest the fuse) using a brown cable. I then connected the N port on the heatlink to the Neutral port on the boiler terminal box (next one along).

The next thing was to connect up ports 2 and 3 from the heatlink (the common and call-for-heat ports). As I went for the low voltage (dry contact) install, these ports needed to be directly connected to ports 1 and 2 on the boiler terminal box (the 2 furthest from the fuse). I therefore connected port 2 on the heatlink to port 1 on the terminal box using a single (blue incidentally) cable, and port 3 on the heatlink to port 2 on the terminal box using another single (brown this time) cable (it would probably be better to use black cabling for this!).

And that was essentially that. The heatlink was installed onto the wall near the boiler and the actual nest Thermostat is in my living room drawing power from a USB cable connected to a standard 3 pin outlet. My old programmer is permanently off as it has been disconnected, and everything is controlled via Nest.

I hope this can be of some help to anyone considering installing their own Nest, but my setup is pretty simple and if yours isn't and you have any doubts, call a professional to install it for you.

In future I will want to connect up a pipe stat and frost stat, but I have no idea how to do this yet.
 
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Unless you would want to put a frost stat somewhere which could be significanly colder than the rest of your house, look at the nest settings for 'safety temperature'. This does the same thing as a frost stat.
 
Thanks mikeyd, my boiler is in an outbuilding attached to the kitchen, and although the pipes in there are insulated the room is not heated so gets much colder than the rest of the house. So I think I will need a frost stat and pipe stat before the winter. If I could figure out an interior temp that marries up with roughly 3C in the outbuilding, then I could set Nest to that interior temp and I'd be indirectly protecting the outhouse pipes too. Hmmmm....
 
I have not checked your model.

But most modern combi boilers do have a built in frost protection and if so this will be mentioned in the service manual.

I am surprised you had such high quotes to fit a Nest. Perhaps you live in a remote area where a lot of travelling is involved, but my standard price is only £84 !

Tony
 
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Hi Tony

Thanks for your reply. I'll take a look and see if there's any mention of a built in frost protection system. I live in Birmingham! So I was really shocked at the quotes too!
 
Yesterday I bought a Nest Learning Thermostat to replace an old programmer at home. I checked with local certified installers and was amazed at the cost of installation. The cheapest quote I received was £120. So, I decided to at least consider trying the installation myself...

Before I start I should stress that our heating setup is relatively simple and that if you have any doubts whatsoever, call in the professionals. So, on to that heating setup. We simply have an aging Baxi 105e combi boiler and a programmer linked directly to it. We didnt have an existing thermostat or extra peripherals such as a pipe stat or frost stat, and no junction box. Based on the simplicity of this setup and prior posts found here and elsewhere I decided to give it a go. I went for the low voltage setup (as described in the nest installation guide and set out below) as this appeared the clearest and simplest option.

The first thing I did was to check the connections on my boiler. These were actually pretty simple. I had a live wire (brown) at the leftmost side (next to the fuse), followed by a neutral wire (blue) in the next position, and a yellow/green earth wire at the next position. These provide the mains electricity supply to my boiler, and are all tied up together in a single grey cable that enters the boiler from outside. On the other side of the terminal block (if we describe the connections I just outlined as supply) I had the same coloured cables running out to the rest of the boiler. Hence, it was pretty simple to see that this was the mains supply setup. I then had two further cables connected at the last two remaining 'supply' side points on the terminal box. These were the connections from my existing programmer (there was also an earth cable from the programmer to the earth point (third along from the left)). So overall the terminal box was laid out as (from left; side with the amp) Live; brown mains supply, Neutral; blue mains supply, Earth; green/yellow mains supply and green/yellow programmer earth, remaining positions 1 and 2; remaining programmer connections.

As we always use hot water on demand (happy to wait 30 seconds for hit water), our programmer was only really necessary for setting our hearing schedule. As Nest takes over this role, I decided to disconnect my current programmer entirely. So, having disconnected all power to the entire house to ensure I couldn't kill myself, I removed the programmer's connections from the boiler terminal box at the earth and points 1 and 2. I capped the cables to secure them and tidied them away. This left only the Live, Neutral and Earth cables from the mains running to the leftmost 3 ports on the terminal box.

Next, I set about wiring up the heatlink. The heatlink does not require its own earth cable, so in terms of providing it with power, only the Live and Neutral were necessary. I connected up the L port on the heatlink to the Live port on the boiler terminal box (nearest the fuse) using a brown cable. I then connected the N port on the heatlink to the Neutral port on the boiler terminal box (next one along).

The next thing was to connect up ports 2 and 3 from the heatlink (the common and call-for-heat ports). As I went for the low voltage (dry contact) install, these ports needed to be directly connected to ports 1 and 2 on the boiler terminal box (the 2 furthest from the fuse). I therefore connected port 2 on the heatlink to port 1 on the terminal box using a single (blue incidentally) cable, and port 3 on the heatlink to port 2 on the terminal box using another single (brown this time) cable (it would probably be better to use black cabling for this!).

And that was essentially that. The heatlink was installed onto the wall near the boiler and the actual nest Thermostat is in my living room drawing power from a USB cable connected to a standard 3 pin outlet. My old programmer is permanently off as it has been disconnected, and everything is controlled via Nest.

I hope this can be of some help to anyone considering installing their own Nest, but my setup is pretty simple and if yours isn't and you have any doubts, call a professional to install it for you.

In future I will want to connect up a pipe stat and frost stat, but I have no idea how to do this yet.
 
I have a Baxi 105he wired up to a danfoss103e5, There is a fused spur next to the programmer that is wired up to the boiler, would i be able to wire a nest up the same as your instalation ? There also is a danfoss rt1 thermostat.
 
Hi,

Don’t want to make constant new threads on this issue but got a couple questions.

I’ve got the 80e which has same lay out at the 105e. Mine has a Grasslin timer attached to it and I’m looking to install the nest.

Installed one in our old place but the lay out was much more labelled than this one.

Would the connections on the right hand side be for the grasslin timer? They all seem to be going into connections on the PCB and I cannot see any cables coming from where the Grasslin timer is at all.

Would I be using the low voltage or 230v diagram for the nest which includes linking live and 2 together in the heat link?



mPg7wD1.jpg


Thanks very much! :)
 
Last edited:

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