I know, I know but it still looks like latin to me :)

[Robert Tyrrell]

Right, I've got the hang of the DuoTech coupled to the NEST but, sadly, I have a problem with an EcoBlue 33 now.

I've wired it as in the diagram attached but I can't seem to get it to fire on the CH. Fine on the DHW. The NEST is working fine, as far as I can tell. It's got 12V from the T1 T2 terminals at both the NEST and the Heatlink, but I just cannot fathom this out.

I've had to use the existing wiring and that's why its got the 3 cable setup as in the diagram, 4 if you count the room stat cable.

So if any of you clever people (I was going to write 'Bright sparks' but I didn't like the pun) can help me out I'd be very grateful.


This was a Keston Celsius with an UVDHW cylinder and my customer wanted it replaced by a combi. Simple I thought
I really should stop counting chickens, it's just that I'm forever the optimist me

 

[Robert Tyrrell]

Any ideas guys and gals?
I'm thinking that I might have the cables to 2 & 3 on the Heatlink the wrong way around as the manual states that the 230 supply at connection 2 (Black wire at boiler) should go to the thermostat.
What I don't understand is how the boiler is feeding power back to the Heatlink, and where from?
I was of the understanding that the 230 went from the FS to the boiler as PL, and Heatlink. The Heatlink then sends 12V DC to the NEST and if it is calling for heat it completes the circuit sending 12V DC back to the Heatlink, which in turn then lets the boiler fire. Have I got this all wrong?

AHA

 

[ShaunCorbs]

what voltage you got at the boiler when the ch is calling ?

 

[Robert Tyrrell]

Thanks for the replay ShaunCorbs - now I know I'm not on my own here
I've got 230 at terminal 2 but on terminal 1 it's just continuity.
I can get the boiler firing for DHW and CH, but only via the chimney sweep settings so I'm thinking that it's something to do with the nest. It's very frustrating but I'll get to the bottom of it, eventually

 

[ShaunCorbs]

Thanks for the replay ShaunCorbs - now I know I'm not on my own here
I've got 230 at terminal 2 but on terminal 1 it's just continuity.
I can get the boiler firing for DHW and CH, but only via the chimney sweep settings so I'm thinking that it's something to do with the nest. It's very frustrating but I'll get to the bottom of it, eventually

No on the boiler white and back wire do you have any voltage ?

 

[Robert Tyrrell]

Could have Sworn that I posted a reply earlier.
Anyway - it turns out that it's. Faulty Heatlink
After. Protracted conversation with the NEST support, and talking to the guy at BAXI, I tried a substitution and it worked. The NEST support people were adamant that it couldn't be the nest but it was so its lucky I bought two ��