On 26/03/2018 14:55, Harry Bloomfield wrote:
Harry Bloomfield was thinking very hard :
Split temp, yup see my other post. If Gremlin95 is about, he knows
more about the new range than I do.

Yes, that's it, 'split temperature' was the expression I was seeking.
Thanks !

Having enquired with both Worcester and Vaillant, neither offers a
regular / conventional boiler which includes an ability to set two
separate output temperatures for heating and hot water. A gap in the
market me thinks, for an enterprising boiler manufacturer.



The 400 used to... Looking at:

https://vaillantgroup.intellirespons...5%2 0-%202015)

You can see that one has the two temperature controls on the front.

However the current model has a radically different internal layout:

https://vaillantgroup.intellirespons... 0-%20Present)

But, a quick read of the manual still suggests that it supports separate
CH and DHW temperature controls:

https://www.vaillant.co.uk/downloads...1-1-931512.pdf

It also still has a connection for an external temperature sensor -
suggesting it ought to work with the weather compensating controls. If
that is true, then it must support split temp operation...

Yup:

https://www.vaillant.co.uk/for-insta...ats-22272.html

Says that it works on all current models.

A single boiler setting stat is fine, where a consumer is happy with a
lower temperature of boiler output for both heating and HW, but less
useful for someone like me who likes their HW hot - where there is a
possibility for some saving on keeping radiator temperatures lower, so
the boiler remains in the more efficient condensing temperature range.

I suppose I could do an add-on stat, mounted on the flow pipe to the
radiators, to shut the boiler down at say 60C leaving the boilers own
stat set to maximum ? Would that not wreck the boiler's efficiency?

My current scheme is to manually tweak the room stat, gradually raising
the room temperature to the desired temperature, over a couple of hours.
Otherwise the heating system over reacts if the stat is set to desired
in one single movement of the dial.

On mine (600 series system boiler) I let the weather compensator chose
the CH flow temp (at installation you can select a variety of response
curves that dictate how aggressively it ramps up the flow temperature in
response to the external temperature falling). That tends to mean for
the parts of the year where it not that cold out, it often runs flow
temperatures in the 40 to 50 degree range.

The DHW I have set to 60 (its set at the boiler - there is no
conventional cylinder stat - just a NTC thermister in a pocket that
connects to the wiring centre). The boiler tends to run flow
temperatures appropriate for that, usually doing the first bit of the
recharge at around 60 to eek out more efficency, then ramping up to 75
ish for the last bit. I also have it set to do an anti-legionella cycle
once per week - where it will heat the cylinder to 75 once. (its a hard
water area, so lower cylinder temps result is less scale deposition).


--
Cheers,

John.

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