Nest E Thermostat Install

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OiOi DIYers

I am looking to install a Nest Thermostat in the house and need a bit of guidance.

I have a logic 30 combi boiler in the loft a controller in the cupboard downstairs and what i think was a room thermostat for a previous under floor heating installation in the living room.

Can i just connect the Nest heatlink to the existing room thermostat wiring or do i need to remove the controller completely and replace with the heatlink ?

If i can utilize the existing thermostat wiring how do i wire it into the controller ?
 

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I read
RF Electronic Programmable Room Thermostat (7 day) kit - Combined 7 day timer and room thermostat with wireless communication to receiver unit which fits into control box of the boiler. Features English language installation help messages. Also OpenTherm Control for gas consumption saving.
but can't see where it connects.
The manual refers to RF Electronic Programmable Room Thermostat (7 day) kit but it does not seem to show how OpenTherm is connected. I assume some add on module.

You can clearly connect as simple off/on, maybe some one will be able to say if there is some module required.
 
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The Next replaces the Invensys controller. Wires in 1 and 3 connect to the two Nest terminals. Other wires must be insulated and not connected to anything.

If that ancient thermostat is still in use it must either be set to maximum or bypassed.
 
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I honestly don't know, we read about OpenTherm but as to how much it saves, not sure, in the main it is a compromise. It simply costs too much to install an ideal system. The aim is to allow the boiler to modulate, (turn down) and to auto cycle, if the boiler cycles when it switches back on it does so at minimum output, if the wall thermostat cycles the boiler then it causes the boiler to restart at maximum output, so main control for a modulating boiler is the thermostatic radiator valve (TRV) the wall thermostat is only there to turn off boiler on warm days.

I have Nest Gen 3, and it seems in USA the nest temperature sensor which are sold in sets of three, can link to Nest Gen 3 and keep boiler running if any of the four selected rooms are not warm enough, but it seems not released in the UK. So as it stands Drayton Wiser, Honeywell Evohome and even Hive are better than Nest.

However Nest e is the only thermostat I know of which does not need a neutral so it is very handy when there is no neutral, but as it stands when Google took over Nest the support for Energenie MiHome TRV heads was dropped, so unless an open plan house i.e. very few doors, Nest is not a good selection.
 
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The Next replaces the Invensys controller. Wires in 1 and 3 connect to the two Nest terminals. Other wires must be insulated and not connected to anything.

If that ancient thermostat is still in use it must either be set to maximum or bypassed.

Hi Flameport,
Many thanks for the response. So literally take just the wires 1 and 3 from the controller back plate and connect those to the heatlink and blank off everything else and job is done ? I assume blank of the fused timer/boiler switch to the left of the controller too ?

Any idea what the wireless performance of the heatlink is like ...... just concious its in a cupboard .... mind you it will be within 10ft of the thermostat.

The antiquated room stat is redundant as far as i am aware. When the mrs decides on the wallpaper we will get rid of it altogether.
 
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So literally take just the wires 1 and 3 from the controller back plate and connect those to the heatlink and blank off everything else and job is done ? I
Yes.
It's just replacing one device with another.
The 'e' version is designed to be as simple as possible, which is why it only has 2 wires.
It's just an on/off switch, which connects the two wires together when heat is required.

Any idea what the wireless performance of the heatlink is like
Far more than any normal installation would need.

I assume blank of the fused timer/boiler switch to the left of the controller too ?
No - as that supplies power to the boiler and controls, and is necessary to isolate those when the boiler is serviced/repaired.
 
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I honestly don't know, we read about OpenTherm but as to how much it saves, not sure, in the main it is a compromise. It simply costs too much to install an ideal system. The aim is to allow the boiler to modulate, (turn down) and to auto cycle, if the boiler cycles when it switches back on it does so at minimum output, if the wall thermostat cycles the boiler then it causes the boiler to restart at maximum output, so main control for a modulating boiler is the thermostatic radiator valve (TRV) the wall thermostat is only there to turn off boiler on warm days.

I have Nest Gen 3, and it seems in USA the nest temperature sensor which are sold in sets of three, can link to Nest Gen 3 and keep boiler running if any of the four selected rooms are not warm enough, but it seems not released in the UK. So as it stands Drayton Wiser, Honeywell Evohome and even Hive are better than Nest.

However Nest e is the only thermostat I know of which does not need a neutral so it is very handy when there is no neutral, but as it stands when Google took over Nest the support for Energenie MiHome TRV heads was dropped, so unless an open plan house i.e. very few doors, Nest is not a good selection.

I doubt i would benefit from anything overly complicated. Its a pretty small semi-detached and we usually just have the heating to come on for an hour or so 3 times a day.
 
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No - as that supplies power to the boiler and controls, and is necessary to isolate those when the boiler is serviced/repaired.

Doh .... I didnt quite think that through .... :)

So what is connected presently is power boiler and power to the controller from the fused switch and 1 and 3 to the boiler in the loft ?
 
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Yes.
It's just replacing one device with another.
The 'e' version is designed to be as simple as possible, which is why it only has 2 wires.
It's just an on/off switch, which connects the two wires together when heat is required.


Far more than any normal installation would need.


No - as that supplies power to the boiler and controls, and is necessary to isolate those when the boiler is serviced/repaired.
Out of curiosity I tried using the old thermostat wiring and the heatlink appears to work i.e it will regulate at the set temperature but what it doesnt seem to do is switch off or on. Have i misunderstood what the Nest does or as you say do I physically need to remove the existing controller. What I want is the ability for the boiler to switch on and off for 1\2 to 1hr maybe 5 times over the course of the day at scheduled times.
 
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looking at the manual there is a maximum (24.3 kW) and minimum (6.1 kW) and the boiler should automatically move between them to suit what the home needs, this is done with the thermostatic radiator valves (TRV) and by-pass valve, not electrical.

There is a flaw in the system in that it can't turn completely off, once down to 6.1 kW it will start to cycle, reducing output further, but when you leave the house better if boiler is not running.

The programmable wall thermostat allows you instead of turning off boiler completely as a programmer would do, you can turn temperature down, so same unit works as both wall thermostat and frost stat. But idea is in winter while in the house it does not turn off.

So my TRV has a program set
upload_2021-11-24_2-26-34.png

And the wall thermostat has same program set, but with slightly higher temperature as higher up the wall than the TRV so the boiler will turn off at 22 hours until house cooled, and also turn off if we leave the house with our mobile phone (geofencing) but with a modulating boiler the TRV is king. Not the wall thermostat.

With my old oil boiler very different, because the boiler does not modulate it can over shoot, also being in the hall the thermostat not in ideal place, so in my case what I am trying to do is insure the boiler fires up multiple times so each room can have time to correct temperature, so I have this upload_2021-11-24_2-36-50.png set, but this is because I have an oil boiler, with modulating gas it would be nearly same as TRV.
 
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looking at the manual there is a maximum (24.3 kW) and minimum (6.1 kW) and the boiler should automatically move between them to suit what the home needs, this is done with the thermostatic radiator valves (TRV) and by-pass valve, not electrical.

There is a flaw in the system in that it can't turn completely off, once down to 6.1 kW it will start to cycle, reducing output further, but when you leave the house better if boiler is not running.

The programmable wall thermostat allows you instead of turning off boiler completely as a programmer would do, you can turn temperature down, so same unit works as both wall thermostat and frost stat. But idea is in winter while in the house it does not turn off.

So my TRV has a program set View attachment 251808
And the wall thermostat has same program set, but with slightly higher temperature as higher up the wall than the TRV so the boiler will turn off at 22 hours until house cooled, and also turn off if we leave the house with our mobile phone (geofencing) but with a modulating boiler the TRV is king. Not the wall thermostat.

With my old oil boiler very different, because the boiler does not modulate it can over shoot, also being in the hall the thermostat not in ideal place, so in my case what I am trying to do is insure the boiler fires up multiple times so each room can have time to correct temperature, so I have this View attachment 251809 set, but this is because I have an oil boiler, with modulating gas it would be nearly same as TRV.

Again thanks for a comprehensive response.

So my existing setup Combi + Programmer + Nest Thermostat will not operate how I am wanting it to through the NEST schedule feature i.e. it switches on at pre-defined times and durations like it was setup on the original programmer ?

You also mention TRV's which I have too albeit just std mechanical ones.

It seems to me you are supposed to just have your heating all day and the Nest just adjusts the temperature throughout the day. I noted there is a feature with it where it supposedly switches off when you leave your home .... at least i think it does .... but that seems to be phone app orientated so i would effectively have to get every family member to install the Nest app ?

Regards the frost stat that has always been in the back of my mind. It is installed in the loft which can get pretty cold in the depths of winter and I have always wondered if it had frost protection. Is there a way to check/ confirm without getting into the boiler unit ?
 
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existing setup Combi + Programmer + Nest Thermostat
Should be just Combi + Nest as Nest does the programming.
Or set programmer to be on 24/7.

My Nest has two ways to see some one is home, either some one walking past it, or mobile phone.

I think the most important thing with modern gas central heating is the lock shield valve and TRV setting.

With my mothers house I used electronic TRV's which made it easier to set, so if a room exceeded the target I closed the lock shield a tad, and once set every room was near enough spot on setting, on leaving new owners did not want the electronic heads, so replaced with mechanical, and now the lock shields set the mechanical worked A1 also.

One should measure the temperature of feed and return pipes, think around 15°C but what I did was turn off lock shield let pipes cool, and then slowly back on until feed pipe got just a little heat, then went to next. I found 20°C = around 2.4 on old TRV.
 
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Should be just Combi + Nest as Nest does the programming.
Or set programmer to be on 24/7.

My Nest has two ways to see some one is home, either some one walking past it, or mobile phone.

I think the most important thing with modern gas central heating is the lock shield valve and TRV setting.

With my mothers house I used electronic TRV's which made it easier to set, so if a room exceeded the target I closed the lock shield a tad, and once set every room was near enough spot on setting, on leaving new owners did not want the electronic heads, so replaced with mechanical, and now the lock shields set the mechanical worked A1 also.

One should measure the temperature of feed and return pipes, think around 15°C but what I did was turn off lock shield let pipes cool, and then slowly back on until feed pipe got just a little heat, then went to next. I found 20°C = around 2.4 on old TRV.

Soz forgot to say, yes i had the existing programmer set to 24/7 but just feel we are burning a lot of gas ..... it isnt a massive property and we are in and out throughout the day so having it running all the time just seems inefficient.

Regards the Nest schedule I am correct in saying it will only switch off IF it detects you are out of the property ?

It would be good if they gave you the option to set the heating to come on and off when you wanted and define the duration. I mistakenly thought that would be the case ?
 
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