On 12/01/2019 09:28, Harry Bloomfield wrote:
John Rumm formulated the question :
IME many of the Vaillant boilers do support split temperature
operation, but it does depends on what controls you have them paired
with.

The 400 series Vaillant I did (probably previous model range, since
this was
= 12 years ago), actually had separate knobs on the front for CH and
DHW flow temperatures. Although that was retrofitted into system with
traditional controls that could not distinguish between the source of
the call for heat - hence the DHW control never came into play and it
ran like your system does.

The blurb on their web site:

https://www.vaillant.co.uk/for-insta...ler-26116.html


Seems to suggest its compatible with the VRC 700 weather compensating
controls, so that ought to allow split temperature as well.

I have studied it and not found any obvious way to split the
temperature. I even spoke to Vailant and they confirmed there was no way
it could be done.

I suspect they are talking nonsense or at crossed purposes. It may be
that it can't be done with the installation you have, however if you are
prepared to add controls then it looks straight forward.

If it (the compensator) is anything like mine (a VR470), then you can
set the temperature for two "uncontrolled"[1] zones, and DHW separately
in the programming. I also have a VR61 control module that lets you
integrate traditional 240V zone valves etc into the controls.

[1] They seem to call what most people would think of as a zone
controlled with valves and a thermostat, an "uncontrolled" zone. They
reserve the term controlled for ones with active blending valves for UFH
where the controls can directly set the UFH zone flow temperature
independently of the main boiler flow temp.

Yup, have a look at:

https://www.vaillant.co.uk/downloads...al-1000027.pdf

See the user manual section 5.2.1.2:

https://www.vaillant.co.uk/downloads...03-1000692.pdf

That definitely allows independent control of CH and DHW temperatures.

(the VR700 has way more toys that you will need - I just picked that one
because it was listed on the 400 series page. I expect the older VR470
would be fine as well)


--
Cheers,

John.

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