On 12/01/2019 11:39, Harry Bloomfield wrote:
dennis@home brought next idea :
IIRC one of the add on controllers allows for different temps when
running HW and heating but I don't recall which.

It would have to be something which interacted directly with the boiler
and Vailant said there was nothing able to do that, when I spoke to
them. The boiler has the built in interfaces for the fancier control
systems, I understand, but little detail to be found about these extra
systems.

One of the problems I found with the Vaillant documentation, was that
there is lots of low level detail stuff, but not so much "big picture"
stuff to tell you what components you need to achieve which jobs.
(perhaps that is what they train their registered installers with!)

In the end it was just a case of reading through all the detail stuff
until you can mentally put together what bits are going to do what you need.

But basically you need a weather compensator, and probably an interface
box to let it communicate with traditional valves etc.

In my case I went for a VR470 and a VR61 (there is also another aux mini
controller / stat to monitor the upstairs temp - but you can do without
that).

You use the VR470 as the interface to configure and control everything
else. It acts as the central point for the timer / stat / weather
compensator, and then a load of other facilities if you want them[1].
The interface box converts the demands of the controller delivered over
eBus, to relays etc that can switch 240V to move 2/3 port valves.


[1] From the handy "cylinder boost", and "holiday mode", to the more
esoteric UFH screed drying programs, DHW anti legionella cycle,
ctrolling aux pumps like secondary circulation pumps or solar collection
pumps etc.






--
Cheers,

John.

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