Nest 3rd Gen Wiring Help on New boiler

[havingalook]

Hi All,Would be great if i could get some help.

Had a new boiler installed worcester 34cdi however didnt have the nest to hand back for plumber to fit so attempted to have a go myself yesterday however it doesnt seem to be working correctly.

I have connected it in the following way (below), the heat link is connected and powered and clicks when i change the temperature however it doesnt actually turn the boiler on ?

connections are in the image and below.

(boiler) Lr - 3 (HL)
(boiler) Ns - N (HL)
(boiler) Ls - L (HL)
(HL) L - 2 (HL)

 

[stem]

Looks OK to me. You don't show the incoming 230V supply but I guess it's connected to N & L at the Heatlink and via the connecting wires also to Ns & Ls at the boiler. For a combi these would have to be present for the hot water to work.

So you need to find out if the Heatlink making terminal 3 (call for heat) live when it clicks on? Are you able to test this with a multimeter? If it is Live, the Heatlink is OK. Then the same test should be made at Lr (Live return) at the boiler.

Also, check that the connections at the Heatlink are secure and that the screws are firmly clamped on the conductor and not the insulation. The Heatlink can be a bit fiddly especially for those not used to making electrical connections in confined spaces.

I assume that the wiring is exactly as shown in your diagram, including the L to 2 link and that there isn't some wiring to an existing room thermostat connected in somewhere.

 

[havingalook]

Thanks for the confirmation, so i have checked all the wires and i think one may have been loose, the double wires into connection 2 on the heatlink.

So i just want the nest to control the radiators, therefore what setting am i supposed to turn the knob to on the boiler? it seems like when i leave it on the lowest setting(frost) the nest doesnt fire up the boiler when i turn the temp above the house temperature on the thermostat, however it does work when the boiler is set at numbe r1 for example?

 

[stem]

The two thermostats have completely different functions:

1. The boiler thermostat controls the temperature of the water. (ie how hot the radiators will be to the touch) The hotter the radiators, the quicker your property will heat up, but they will continue to give heat off this extra heat as they cool once the Nest has switched them off, so may overheat the rooms in milder weather. If it's set too low, it may not provide enough heat in cold weather.

Condensing boilers tend to be more efficient at lower temperatures, so set it as low as you can so that your house still gets warm enough. As estimate perhaps 2 to 3 in mild weather, and 4 to 5 in cold weather, but much will depend upon the size of your rooms, radiators and the level of insulation in your home.

On the frost setting, as the name suggests, it is there to stop the water in the boiler freezing, so it won't provide any heat at all until the temperature drops low enough to pose a risk of it doing so.

2. The Nest thermostat controls the room temperature.