Nest not working to control the boiler

[easysteve]

Hi 

I've a Potterton Powermax boiler 155x and I've replaced the  PRP thermostat with  a Nest as per this blog http://needsmorepolish.blogspot.com/2018/03/fixing-heating-upgrading-to-nest.html

The Heatlink powers up, but does not seem to control the boiler. Also I notice that if the time on the boiler is set to off, then obviously the Heatlink will power down as there is now no power going o the Heatlink .  If i leave the boilers time on say 24hr, then the Heatlink will stay on .. but the boiler will continue to keep the water hot throughout the night- wasting gas... and the Nest still does not switch the boiler on /off. Any clues to what's wrong?

[Frustratedddd]

The first thing to check is the power into the Heat Link.

Far left should be a 24hr Neutral, then 24hr Live, this should be fed from a power source fused down. Not switched at all, just a live/neut supply. [This is NOT powered from your boiler circuit]

Then a looped wire from Terminal L to Terminal 2, this gives you a feed to the heating relay.

Do you have that?

[easysteve]

No, the live & neutral seem to be fed from the boiler to where the old thermostat was as the power goes of if I  switch the boiler's timer from 24hr to timed.

[easysteve]

... Once I sort out the wiring .. do I leave the boilers timer on 24hr.. or disconnect completely?

[Frustratedddd]

That is your first problem, you need a constant feed to the input terminals, L&N

You can do either, depends if you want to get rid of the timer or happy to just leave it there.

Remove timer and everything works from the Nest.

Keep the timer, you will need to change settings to 24hr - constant.

[CristianC]

Hi there,

It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.

[AlexD]

Hi @easysteve , sorry for the late reply. If you have a 3rd Generation Google Nest thermosat you can check out some wiring examples here: https://bit.ly/3nt2N4t . 

As Frustratedddd mentioned you will need constant power connected to the N/L terminals and you will usually have to set the timer on the boiler, or if you have a separate programer, to be constantly on. If possible it is best to have it removed. 

[AlexD]

Hi, I wanted to check in. Do you need any further assistance? If so, make sure to let me know.