Nest 3rd Gen Install

[DVK]

Hi guys. I have exactly the same programmer and boiler (though it is also a 1 year old Taylor Wimpey house)
After speaking to Nest, he game me the impression the Heat Link would physically replace the programmer, then I would just install the Nest Thermostat where the old Thermostat is?
Is this wrong, would the the Heat Link have to be installed closer to the boiler or tank?

Thanks

 

[dantanner]

Hi does anyone know if I can simply replace the old thermostat with NEST?

My boiler is a IDEAL HEAT LOGIC 15

Nest suggested that this is the case however IDEAL say it wont work with nest?

 

[muggles]

It will work, but you need to wire it into the wiring centre, not your boiler

 

[Steve Walker]

I have the same setup with a David Wilson home. I have replaced the old programmer with the heat link with the following(from searching on other people's setups) all n wires grouped and a single wire going to n. All the l wires groups and a single wire going to the l. A link wire from live to 2 and 5. Call for heat in 3 and call for water in 6. Heating works fine but hot water won't fire the boiler. I have tried to troubleshoot and put call for heating into the water one and it fires the boiler but water won't fire from either. Any idea why?

 

[stem]

That sounds right, a permanent live on 5 'Hot Water Common' and the 'Hot water Call for Heat' in 6. All I can suggest is:

1. Maybe the hot water cylinder is still hot so that the cylinder thermostat is not calling for heat. Try turning it up, or
2. The wires in the Heatlink are not connected properly. They can be a bit fiddly. Are the screws tightly on the conductors and not the insulation?

 

[Steve Walker]

I will try that. It's weird because the valve makes a noise when thermostat clicks but the boiler doesn't fire and if I move the valve manually the boiler still doesn't fire.

 

[stem]

By "valve" do you mean a two port (not a 3 port) motorised valve?

If so, it's easy to check that the valve is operating. when the Nest is switches the hot water on, after a few seconds can the operating lever be moved freely without any resistance? If so, the valve is opening and the Nest is doing its job, so the problem is elsewhere.

Inside the motorised valve is a small microswitch, when the valve opens, it operates the microswitch and the microswitch controls the boiler. These microswitches can fail, so the valve may be opening but not starting the boiler. It may have been like this for sometime and you haven't noticed before because the central heating will start the boiler and as the hot water valve is open the hot water cylinder will heat up.

 

[Steve Walker]

Yes 2 port valve. It's a good point as it's been cold so the heating has been on loads. It the only thing left because as you say the valve moves when I call it for hot water but no boiler firing. Thanks for your help.

 

[Steve Walker]

All sorted.after checking power to the cables and tracing it back I realised the live wires were setup wrong which is why only heat was working as it was making a circuit. I had my new kitchen installed and the builder had taken all the labels off the wires when he fitted the splashback! Thanks so much for your help.