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Brian Sharrock wrote:
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Now, if the exchanger is in the top part of the cylinder, the mains
pressure cold water comes into the bottom of the heat exchanger, which
is halfway up the tank, and will meet tank water temp of somewhere
between 10 and 65C, lets say maybe 35-40C. What this means is at end of
useful hot output, the water below the heat exchnager will be about the
same temp as it was before HW was drawn off, namely a gradient from 10C
to 40C.

Dubious conslusion: the HPE accepts fluid from the very top of the
cylinder -
it's physical location is irrelevant. For practical purposes it's
apposite
to install it onto the cylinder removed from the penetrations -hence
'mine'
is mounted about 'half-way-up' ... but it's fed off apertures at the top
and
bottom. Your other surmises are premised on a dodgy conclusion.

Only trouble is, I think we're talking about 2 different things there.
I was specifically talking about the other type of system, where the
water runs through a heat exchanger located inside the tank. Things
will be a bit different with your external exchanger setup.


OK! From your usage of the phrase "the heat exchanger, which is halfway up
the tank"
as opposed to 'immersed heating coil', I inferred you were referring to an
external plate heat exchanger. BTW; your observations was one ot the reasons
why I 'rejected' that design in my 'procurement' policy.

I'm not sure if I've explained it too good!

Me too; I hope I've explained it as well.

Well, at least the fluid vs water terms help.


OK ! I personally found the hot water here- cold water there- _very_
confusing, particularly trying to determine where the water in the boiler
versus the water in the bath were ... so I instructed myself to cite one as
a fluid ( system, heat transfer, ...water) and the other as water (potable,
warm or cold). With these differentiated the penny dropped .... and I
purchased a vented, heatbank which operates the CH and DHW .... and clears
the loft of a cold water storage tank.

--

BRian


NT