Vaillant ecoTEC Plus, VR66/2, and Mixergy cylinder

[Notagain!]

Hi all,

A plumber has fitted (on his recommendation) the following set up:

Boiler: Vaillant ecoTEC Plus 2 620
Controls: Vaillant sensoCOMFORT VRC 720F (including weather compensation)
Wiring Centre: Vaillant VR66/2
Cylinder: Mixergy MX150 Indirect

All was in and well from a central heating perspective, but the plumber was not able to get the Mixergy call for heat to register a demand with the boiler. This should be configured with PDHW whenever a call is made from the Mixergy.

After many (so many…) hours on the phone to both Vaillant and Mixergy, we have the current suggestion from Mixergy on how to wire the cylinder using the cylinder stat terminal:

Mixergy indirect cable:

Black core to VR66 CYL number 2
Brown core to VR66 CYL number 1

Due to being volt free you shouldn’t need to connect the grey/earth connections, but I would recommend making the grey safe and linking the earth in with one of the other earth connections on the VR66 wiring centre just in case.

Hot water 2 port valve:

Earth cable to DHW ON Earth connection
Neutral cable to DHW ON Neutral connection
Brown cable to DHW ON Live connection

The Grey/white and orange cables left unconnected and made safe.


This was tried with the hot water schedule set to 24/7 (and boost as well), but has not worked. In addition, the boiler has now developed an F.105 error (gas valve alignment), for which we cannot find any info online or via the Vaillant service centre.

Does anyone have experience with this set up?

Thanks in advance,

Notagain!

 

[CBW]

Sounds like a wiring fault. @ScottishGasMan or @Sim777 might be your ones for this.

 

[Notagain!]

Thanks CBW!

As it is under 2 weeks old, I assume this will be a warranty call.

Do you have any idea on the wiring for PDHW and the Mixergy using the cylinder stat?

 

[CBW]

I assume this will be a warranty call.

Not sure, as it might be a non warranty call being a potential wiring fault

Do you have any idea on the wiring for PDHW and the Mixergy using the cylinder stat?

No, sorry, never done it, which is why I’ve linked the 2 others in.

 

[Notagain!]

Not sure, as it might be a non warranty call being a potential wiring fault

No, sorry, never done it, which is why I’ve linked the 2 others in.

Sorry if this is an obvious thing, but would you think this would be a wiring issue in the wiring centre, or in the boiler iteself?

Thank you for tagging the others, much appreciated!

 

[CBW]

Not entirely sure, as I’ve never wired them up, especially as pdhw

 

[Sim777]

No idea, I steer well clear of Mixergy as it is just an over complicated bit of kit for such a simple task as water heating.

vaillant wants to use its own temp probe which I don’t think you can do on mixergy - it’s all unnecessarily too complex with mixergy

 

[ScottishGasMan]

I'd not touch the Mixergy stuff myself either, Not sure how their system wires in.

Normal vaillant control set up would be very simple, there would be 1 sensor that slots into the cylinder pocket and wires back to the vaillant equipment and from their the vaillant control can see the exact temperature of the cylinder and work it from their. The complication comes from the mixergy.