Another Nest installation thread

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Hi all

I'll try and keep your frustration to a minimum by starting out with:
- I'm not trying to cheap out on getting someone in to install my new Nest HeatLink and Thermostat by doing it myself
- I would however love to try and do it myself
- I'm mainly just naturally inquisitive, so even if I can't do it myself I'd love to understand it better, hoping you can help me with that!

I've moved into a new build. Two zoned heating with two wired "ESI ESRDT3" thermostats. "ESI ES3247B" 3-channel programmer in the utility room. Hot water tank in the cupboard upstairs. Would like to install Nest thermostats

Looking through the instructions it actually looked like a relatively simple job that I was looking forward to attacking - I took the front cover off the circuit board that sits on my hot water tank and am confused by the fact that the Live and Neutral terminals for both thermostats aren't connected to anything, only "Normally Open / N/O" is connected to them. Does this mean they're powered separately from mains wiring rather than going through this board, and I therefore can't (easily) use them in wired mode in the same place as my existing room stats? The stats themselves have Live, Neutral, and N/O which are all wired up

Pic of board:
http://i.imgur.com/iGgR1eP.jpg

Thanks for any info - much appreciated :)
 
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The existing thermostats are battery powered, and therefore do not have or require mains power.
However as you are replacing them, this doesn't matter in the slightest.

The Nest heatlink replaces the existing programmer. The Nest thermostat connects to it wirelessly.
As you have 2 heating zones, 2 Nests/heatlinks will be required if you want to control each zone separately.
 
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Crossed wires I think - there are no batteries in the thermostats themselves (the battery sockets are there but empty), they are wired to Live, Neutral, and N/O so I assume the N/O goes to the board and the Live and Neutral are coming from the mains supply separately, they've just elected not to wire it from the board

This means then that I'll need to supply USB power to the new Nest thermostat, and can't easily replace them in situ?
 
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http://www.esicontrols.co.uk/esrtd2.html

Technical Data
Digital Room Thermostat with TPI ESRTD2
Temperature Control Class ErP Class IV Product (2%)
Energy Efficiency Technology
TPI (Chrono-proportional) Control
Fixing Easy fit back plate
Power Supply 2 x AA/1.5V alkaline batteries (LR6, MN1500 type)
Sensing Element Electronic
Switch Rating 3(1)A 230VAC (volt free) ( this is the rating on the switch in the thermostat, it is NOT the power supply )
Temperature setting Range 5°C to 30°C
Terminal Differential <0.6° C at 4°/hour
Switch type S.P.D.T.
Dimensions L85mm x H85mm x D35mm
Complies with: EN60730-1, EN60730-2.7, EMC Directive 2004/108/EC, LVD Directive 2006/95/EC
 
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I'm a bit shocked. Someone's actually wired up heating controls using the cordgrips, earth wires to earth terminals, and sleeved the switched live!

(shame they pinched the insulation by routing the wires over the terminal block rather than around)
 
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OK so think I've got to the bottom of this now - I will need to remove the existing stats and patch up the holes, and have my Nests powered up by USB separately on a stand somewhere

One thing I can't understand about the existing system that I'm curious about is: at a basic level, the programmer controls when the thermostats work (i.e. if the heating is off at the programmer, you can't get a little flame to appear on the thermostat and call for heat). How does this work? Bearing in mind the circuit board on the cylinder only has one wire coming from the programmer (HW ON), how does the programmer communicate with the thermostats? Is there more wiring within the boiler in the garage?
 
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I have also looked at the power requirement for Nest it seems 5 volt on some paperwork and 12 volt on other likely either can be used. However the Nest is a IFTTT device which can integrate with eTRV's so not sure at to if you would need two or not?

I am still to fit Nest, I fitted a couple of eTRV's and to be frank they did not work as expected. I realise it's not the eTRV's fault, it was me expecting too much. I thought I could change temperatures during the day, giving a warm room in the day, slightly warmer in evening, then cooling at night, however the fabric of the building stores more heat than I realised and although the eTRV heats up OK, it does not cool down that fast, so the whole idea of saving energy and more to point having room at exactly the temperature required simply did not work, the morning sun through the bay window heats up the room what ever controls I fit.

The house is simply too slow to cool down for the eTRV's to control the room at different temperatures through the day, it's not the eTRV's fault, it is the design of the house. So really the standard TRV does a reasonable job.

There is a huge difference between TRV control and room thermostat control, the room thermostat turns the boiler off and on so will always have a hysteresis problem, the good TRV adjusts the flow neither turning fully on or off but maintaining the temperature. The boiler is designed to work with TRV's and the flame height alters to suit the demand, so the rooms are held at a near constant temperature. The room thermostat is really for when the TRV fails to maintain the temperature in the summer months as although most boilers do have anti-cycle software they still tend to fire up when not required.

This is were the system falls down, if we change the wall thermostat then we also need to adjust all the TRV's to suit. Using the complete off function of Nest or complete On function while a work will work, but varying the temperature during the day will not unless you use eTRV's which can be set to follow the Nest thermostat. And once eTRV's are used then the room temperatures can be set with the phone without using Nest. Although Nest does help as it ensures the boiler fires up, but it is the eTRV's which control room temperature.

I wish I had realised how slow the house cooled, I should have realised, when the old thermostat failed it took some 6 hours before I realised it was a little cold in the room, it does depend on the house, my first house had hot air ducted around the house, and that house would have worked A1 with Nest, but here in my mothers house I have found there is no real point in eTRV's or any other thermostat to raise and lower temperature during the day, as the house simply takes too long to cool down.

In my own house the Myson radiators work well at rapid heating of house, but they are old and do not integrate with new systems. 30 years ago when fitted they were something special, today it would not take too much to include a time switch in each radiator, but as far as operating from phone goes I can forget it.

In mothers house I still want to fit Nest, however the eTRV's come first, with every house I have lived in, except for one with hot air central heating, the wind and sun has resulted in rooms not being constant temperatures in relation with each other, so the heat required in each room varies with the weather, even with two zones you still need the TRV to adjust heating for wind direction and sun. So to my mind the eTRV comes first, then the thermostat which will integrate with the eTRV. For some reason when mothers central heating was fitted only two down stairs rooms had TRV's fitted, as summer comes I want to drain system and fit the missing TRV's then I can fit the Nest in the main room.
 
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how does the programmer communicate with the thermostats?
There is no 'communication' - both the programmer and thermostat are just switches.
When the programmer is on, power goes to the thermostat contact. When the thermostat senses that heat is required, power from that continues to the valve for the particular heating zone which then opens, another switch inside the valve then activates the boiler.
If the thermostat or programmer are off, there is no power to the valve which closes due to a spring inside.

The Nest and others are a switch in a box which is controlled by the remote thermostat.
 
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Now I'm a bit better armed with the info (thanks!) the instructions look quite clear, think I will give this a go myself

Looks like I just need to hook up Live and Neutral, Call for Heat (HW) where the programmer wire currently goes, Call for Heat (CH) where the zone 1 stat N/O currently goes

Going to pick up some 5 core 1mm2 cable to make these connections
 
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Probably should have bought 0.75mm cable as the 1mm was a bit tight in the tiny terminals on the Nest, but nevertheless got it all installed and working.

Thanks for all of your help and advice, not only in how to get it going but also helping me understand how the existing heating system works, my curiosity has been satisfied! :)

As a note for anyone stumbling across this thread, I also had to jumper both "common" connections to Live as per the wiring diagram (I stupidly missed this step originally and it didn't work)

Just need to wait for the Mrs to get home and be suitably unimpressed that I've spent my morning messing about with that rather then the list of jobs she gave me
 
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Hello.
I came across your thread while trying to find out the exact same thing.
I'm gonna guess you moved into a RedRow home, or it's just coincidence you have the exact same equipment as I do.
I can tell by your post you are a keen "DIYer"... but I can't say the same about me.
So, long story short, would you mind explaining in short steps what you had to do to fit your Nest thermostat and Heat link at your place?
Thanks!
 
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Hi mate

It's actually a Taylor Wimpey place but assume they're all using the same kit

It was pretty simple in the end. Pick yourself up some 0.75mm cable and some wire cutters/strippers

I'll have another look at it tonight and try and give you a hand with it

Cheers
Jim
 
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