On 25/05/2022 09:17, RJH wrote:
> On 25 May 2022 at 09:08:10 BST, "RJH" <
patch...@gmx.com> wrote:
>
>> On 10 May 2022 at 20:19:31 BST, "Ben Blaukopf" <
b...@blaukopf.com> wrote:
>>
>>> Just for information, because
>>>
>>> a) It wasn't totally obvious that this would work
>>> b) The manual is extremely light on details
>>> c) There is no info I could find on the web about the V4043B wiring.
>>>
>>> Had an Ideal Logic System 24 Max boiler installed.
>>>
>>> I set it up as a PDHW system.
>>
>> I've the same boiler (well, Logic 24+) and thought about this, but figured it
>> might put undue stress on it as it didn't *appear* to be a design feature.
>>
>
> Oops, idiot that I am, that's a system boiler, mine's a combi. Of course it
> wouldn't work on mine. Probably ;-)
It is in theory possible to run a zoned DHW cylinder on a combi - and it
would make some sense in a place like mine where the boiler is at the
end of the house adjacent to the kitchen, and the bathrooms and cylinder
are in the middle of the house. You could have an unvented cylinder
near the bathrooms for high flow low lag delivery there, and the DHW
output from the boiler to the kitchen for lower flow but again low lag
and potable hot water.
The trick would be getting all the toys (i.e. controls) to play nice
together if you want split temperature operation on top of weather
compensation. I did toy with doing it on my setup, but could not quite
convince myself that the Vaillant controls would cope (they probably
could - but their system level documentation leaves a bit to be
desired!) So I went with a system boiler in the end.
>
>> Also, at least IMHE, be wary of the weather compensation. As winter tailed out
>> and it was still cool indoors, but 10C outside, the heating was very
>> ineffective, with the radiators at c.40C. It might be that my house is just
>> cold, or I bought a cheap (it was) and poorly designed unit. There's a picture
>> of the slopes amongst the pics here:
>>
>>
https://www.icloud.com/sharedalbum/#B0zJRveFpJIHZzz
>>
>> Still, I'd be interested to find out how you find it - may well revisit.
>> Washing up quantities of hot water are a pain as it is.
It sounds like you need to pick a steeper curve. On mine I think it came
preset to curve 1.2, which would give a flow temp of 41-42 ish for a 10
degree outside temp, and I found that was not quite enough. So I
switched it to 1.8 IIRC - and that gives a flow temp of about 46, which
is enough IME.
http://wiki.diyfaq.org.uk/index.php/File:VaillantVRC470HeatingCurve1.png