Nest 3rd Gen on Y plan Boiler system- One last question before I pull the trigger to purchase :)

[darklegend11]

Hi all

I would like to say firstly this is a wonderful and knowledgable community and forum. I learnt a lot on installing the Nest 3rd Gen and love how people get stuck in and help each other.

I would say I’m 80% sure on all the cable and works involved at installing Nest 3rd Gen. the other 20% involves me installing the actual Thermo stat.

So to conclude it I originally want to install the new Thermostat at the existing location but found out the cable goes to the junction box upstairs and there’s no link to the existing programmer so I’m thinking about installing the thermostat in a different location using the plug instead. However reading on this forum a lot of people said you need to disconnect the old thermostat cables and reconnect to stop an open circuit.... this part confuses more. I need to trace the cable which isn’t a problem just need to eliminate and check which one is the thermostat but unsure on what to do next. Some suggested reconnecting the live from the programmer? Or something... would someone take a look at the cable on the thermostat follow by the junction box? And maybe tell me a step guide on what to do with the cables on the old thermostat?

Y-plan boiler
Drayton programmer and Honeywell thermostat

1st picture thermostat
2nd picture junction box
3rd picture programmer

Thanks for all your help.

 

[stem]

There are several options available to you. I have drawn you a sketch of each. Number 3 is the way a professional would do it and it allows the existing thermostat and its cable to be removed completely. Number 1 is the easiest, but the existing thermostat would remain in place. Electrically speaking they all achieve exactly the same thing. [S/L= Switched Live, which is the yellow wire]

 

[darklegend11]

Hi Stem

Thankyou for your prompt response.
I may go for option 1 purely because if we were to move house in the future then It will save wiring back the thermostat cables back in.

Am I right to confirm that option 1 doesn’t require me touching the junction box but I just need to open the existing thermostat in the hall way as shown on picture 1 and wire the yellow cable from (3) into the live wire?

Thanks

 

[stem]

Correct. Simply move the yellow wire from the thermostat terminal (3) and put it in (L) along with the red. That's all you have to do.

The thermostat may appear to work and you may even hear it click occasionally, but it won't actually be doing anything. As long as the Nest Receiver replaces the existing programmer, it will have sole control of the heating.

 

[darklegend11]

Hi Stem

Thankyou, You have been very helpful and kind to help me out. Out of curiosity option 3 where you state remove old thermo stat and cable, then link where brown, yellow and red came from are u referring to the cable for programmer?....

Looking at my junction box I’m pretty sure the thermostat is connected to the right hand side.... but if I do choose this option, I don’t see brown but only blue, red and yellow? Am i misreading somewhere? Sorry to be a pain :-/

Looking at the junction box upstairs and picture 2 I can see there’s both red cable connected to terminal (12) I assume this is where both programmer and thermostat’s live wire?

Thinking about when I move house I want to do a professional job

Hope I’m not asking stupid questions?

 

[stem]

With option 3, It's the cable that goes to the thermostat that can be removed as it is no longer being used.

The yellow wire from the thermostat, should be the one connected to the white wire going to the motorised valve at the wiring centre. That will identify the thermostat cable for you. But check it to be sure.

The cables that presently go to the programmer will need to stay as they will go to the Hive receiver which replaces it.

Sorry the reference to brown was a typo. I have corrected the drawing.

 

[darklegend11]

I got it!!!
Thankyou Stem.

Only problem now is I have to wait for when the Nest goes on sale again, it went down to £150 for Black Friday but I missed out on the opportunity.... hopefully come Xmas it will go for sale again??

Do you know anywhere I can get it cheap?

Thanks for your help once again.