Nest Thermostat 3rd gen

[Sat22]

Hi, I am installing a nest thermostat 3rd generation. It is a conventional boiler with only 2 pipes going down. Pic attached. It’s controlled by a programmer upstairs and a thermostat in the hall. I’ve taken the old programmer off. And I have these wires. Pic attached. I wired the heatlink, connected everything got the green light but heating wouldn’t come on. Any ideas? Is it because the old thermostat is still wired in?

 

[James]

Looking at it, I think you have the wiring wrong on the nest heat link.
The thermostat should be removed and safely terminated, often the original wires can be used to power the nest unit.

There will also be a wiring centre, often near the hot water tank, some changes might need to be made there.

 

[Sat22]

Looking at it, I think you have the wiring wrong on the nest heat link.
The thermostat should be removed and safely terminated, often the original wires can be used to power the nest unit.

There will also be a wiring centre, often near the hot water tank, some changes might need to be made there.

Thank you ??

 

[Rockingit]

The original thermostat needs taking out of the system - or - you preserve the wiring and use it to power the nest thermostat +12v and mount in it's place (all in the instruction book).

Generally speaking, the Nest Hub will just piggy-back off the existing 2ch wiring into the old time clock.

 

[Sat22]

The original thermostat needs taking out of the system - or - you preserve the wiring and use it to power the nest thermostat +12v and mount in it's place (all in the instruction book).

Generally speaking, the Nest Hub will just piggy-back off the existing 2ch wiring into the old time clock.

Thank you ??

 

[freddo]

I've no idea what wiring diagram you followed to get to that but it's a long way off! You appear to have a 'Y' plan heating system, there is a Y plan diagram provided in the Nest manual.

 

[Sat22]

I've no idea what wiring diagram you followed to get to that but it's a long way off! You appear to have a 'Y' plan heating system, there is a Y plan diagram provided in the Nest manual.

Thank you. All done. Great forum

 

[Rockingit]

Thank you. All done. Great forum

Glad we could help! And, enjoy your Nest (which I would have to say, being a Nest installer and personal user!)

 

[Fogbutt]

I have a nest 2 learning controller with nest link. I have been offerered a nest 3 learning controller thermostat without a heat link. Could I just add the nest 3 to the system and use the heat link that i have?