Nest to replace Potterton Programmer and thermostat

[johnpeng]

Hi,
I have bought a Nest thermostat recently. The quoted price for installation is above 90 pounds in my region. Heard from lots of people that the nest installation might be not difficult, thus, would like to give it a try with your advice.

My CH and HW system: Y-Plan (3-port), Potterton boiler and Programmer are in kitchen with switches; Potterton thermostat for CH is in living room; Hot Water tank is on the first floor airing cupboard (there is a control box and Potterton thermostat for HW next to it, which is set to 60 degree).

My plan is to replace the programmer with heat link, and abandon the existing thermostats, instead, using the Nest stand to place the nest thermostat in the living room.

I woud like to ask help for wiring (I am looking for the simplest way to install):
1. Is my proposed wiring for heat link correct (from old programmer)? Does it mean the new wiring is able to control CH and HW On/Off, Timing, and the central heating temperature?
2. I do not need control HW temperature, just need control the timed ON/OFF. Of course, if Nest can control HW temperature with just replacing then programmer, then that would be great.

I still did not know how the thermostat works. What is the relationship between thermostat and programmer? I hope the installation only involves in replacing the programmer. Or else, that would be beyond my capability.

I am looking forward to having your help. THANK YOU!

Boiler:

Programmer:

Living room thermostat:

Hot Water tank, control box and HW thermostat:

My proposed wiring:

 

[Devonchris]

This may help

How to install the Nest Learning Thermostat (3rd Gen) in a Y-Plan System | Life of Man - http://lifeofman.co.uk/2017/06/install-nest-learning-thermostat-3rd-gen-y-plan-system/

Or it may not. In which case it will cost a lot more than £90 for an electrician to sort out any errors you make.

 

[johnpeng]

Thank you! I had read the blog and understood all but one. Since I just want to install thermostat on the Nest stand, could I just disconnect the existing thermostat, and wipe close the cables with tapes (not use)? I still wish to leave the existing thermostat on the wall, or else there will be a big hole.

I would appreciate if anyone could help explain it.

 

[Devonchris]

The time switch is only one part of a more complex system. basically, the programmer is a switch which sends a signal to another switch, (the thermostat) which sends a signal to another switch (the zone valve) which sends a signal the boiler and pump to fire up. If any of the switches are open then the boiler is off. Unless any of the other circuits want it on, as you don't have a separate boiler for heating and water. This is why a zone valve is fitted, it is this that controls where the hot water goes and not the boiler.

With a Y plan only one zone valve is fitted which makes the wiring a little more complicated.

If you remove/ blank off the thermostat wiring the Nest will have no means of communicating with the boiler.

Have a look at this

If you don't understand it then I would leave your screwdriver in the drawer.

Ps. I'm not an electrician or a technical author so if this sounds complicated good. All usual disclaimers included.

 

[Sparkie30]

It is a bit involved nest doent control hw temp stat on tank does. You will also need to use the cables for stat as it requires 12v dc unless you dont like existing place.

Just a tip when wiring nest on tank stat you have c 1 2. 1 fires your boiler.

Good luck

 

[johnpeng]

Okay, then I might consider to connect the existing thermostat wires to Nest thermostat, though I will have to check the voltage which should be 12v for nest thermostat.

Am I right?

The time switch is only one part of a more complex system. basically, the programmer is a switch which sends a signal to another switch, (the thermostat) which sends a signal to another switch (the zone valve) which sends a signal the boiler and pump to fire up. If any of the switches are open then the boiler is off. Unless any of the other circuits want it on, as you don't have a separate boiler for heating and water. This is why a zone valve is fitted, it is this that controls where the hot water goes and not the boiler.

With a Y plan only one zone valve is fitted which makes the wiring a little more complicated.

If you remove/ blank off the thermostat wiring the Nest will have no means of communicating with the boiler.

Have a look at this

If you don't understand it then I would leave your screwdriver in the drawer.

Ps. I'm not an electrician or a technical author so if this sounds complicated good. All usual disclaimers included.

 

[Devonchris]

I'm not an electrician. This is an electricians forum, therefore I'm just a guest. Whilst I may, from time to time, point people in the right direction for information, particularly with regulations etc. I can't tell you which wire to put where.

I believe that if you are competent enough to install this then there is sufficient info in the thread, therefore, I'm out.

As Sparkie30 has said, good luck. I wish you well. Please don't take any unnecessary risk.

 

[Madocks]

£90 for a Y plan is a decent price