Nest Heat link to Alpha eco2

[Thue]

Hi everyone, I'm new to the forum but I've been reading it for quite a while and I thought I would register today as I was looking to get some help on a problem and I couldn't find the solution online.

I recently purchased a Nest thermostat (2nd gen), and I wanted to wire it up to the boiler myself. I have an Alpha eco2 boiler with a wireless thermostat at the moment, and I'm struggling to figure out which cables should I connect to the Nest Heat link. The thermostat connects to a Comfort receiver, which is cabled in with 4 cables labeled 1,2,3 and 4.

I've included below a picture from the boiler's manual showing the wiring diagram, at the moment the wireless receiver seems to be connected in place of the programmer clock from the diagram (top left); I'm also including the wiring diagram for the heat link.





Any help in figuring this out would be really appreciated, thanks!

 

[flameport]

Any existing clock/programmer/thermostat is removed.
Nest requires permanent power on L&N connected to the L&N terminals in the boiler, then 1&2 in the boiler connect to 2&3 in the Nest.

 

[Thue]

Hi Flameport, many thanks for your help.

Should I connect the wires that are on the top or on the bottom?

The L&N wires are connected to the mains on the bottom and to the boiler on the top, I assume I have to disconnect the top ones and have them go to the Nest? Same for 1&2?

I've attached a picture of the current wiring (with the receiver still connected) just in case too.



Thanks!

 

[Thue]

Just an update, I connected L and N on the heat link using the old wires coming off of the receiver, and then connected the remaining 2 red wires to the common and call to heat on the link.

The nest link switches on and connects to the nest thermostat wirelessely, but the led on it keeps blinking and the nest is not able to switch the heating on and off.

I'm guessing the red wires coming off of the receiver were not the right ones, but they should be the ones connected to 1 and 2 from the boiler? What am I doing wrong here?

 

[jackthom]

Are the red wires you connected to the Heatlink 'common' and 'call for heat' the ones marked 3 & 4 on the old comfort receiver?

First of all try (safely) connecting up those two reds directly together to check that the boiler then fires up.

If that works the Heatlink should be able to do the switching when those wires are connected to Heatlink 2 & 3.

 

[Thue]

Hi Jackthom, yes they are 3 and 4 on the old receiver, and I've connected them to Heatlink 2 and 3.

I assume they are interchangeable? I'll try connecting them together and see if the boiler starts that way, I'll keep you updated, thanks very much for your help in the meantime!

 

[jackthom]

If the boiler fired OK with a direct connection and the problem looks like it's with the Nest take a look at this..

https://nest.com/uk/support/article/What-does-the-light-on-Heat-Link-mean

 

[Thue]

I just checked the meaning of the blinking light and apparently the heat link couldn't connect to the wifi. After restarting it everything seems to be working now!

Many thanks for your help!