I'd have thought that this was a little academic, unless the person is
incredibly stupid and sets thermostats to try to make the tank into a steam
engine. also does not say how far this 15mm runs for and what the cylinder
is supposed to be feeding either.

Yes I've not come across unvented certificates, only the people issuing
things tend to vent a lot...:-)

Brian

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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Roger Hayter" wrote in message
...
wrote:

On Friday, 13 April 2018 21:44:06 UTC+1, Jonno wrote: I want to
install
a direct un-vented hot water cylinder in a flat. The install
instructions call for 22mm diameter water supply line, the main riser
supply to the building is 22m and then reduces to 15mm before the stop
valve. Do i need to isolate the main riser into the building in order
to
replace the 15mm stop valve with 22mm or can I step up the pipe
diameter back to 22m after the 15mm stop valve without affecting the
performance of the cylinder.

15mm is likely to give unsatisfactory flow.

If the unvented cylinder is over 15 litres you must have an Unvented Hot
Water certificate to do this work.

Owain

I rather like the idea of an unvented certificate. Is that really it's
name?

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Roger Hayter