In an earlier contribution to this discussion,
Brianb wrote:

I've just read
the thread on Thermal Store vs. Heat Store, but can't say that I fully
understand how each works. How do these differ from a Pressurised
Unvented
HW cylinder such as these

http://www.discountedheating.co.uk/s...Cylinders.html

AIUI, a thermal store and heat bank are very similar, but they differ from
an unvented cylinder.

The all provide mains pressure hot water, but they do it in different ways.
In an unvented cylinder, *all* the hot water in it is at mains pressure -
thus requiring no cold header tank. There are a lot of safety issues with
this arrangement, and these tanks can only legally be installed by people
with the right qualifications.

In a thermal store/heat bank, the hot water is at only just above atmosheric
pressure (just like a conventional cylinder) but there is a large heat
exchanger *inside* through which mains- pressure cold water passes on its
way to the hot taps - getting heated as it passes through.

This type of installation is legally D-I-Y-able.

The store may possibily have yet another internal heat exchanger for heating
the the central heating water - enabling the boiler to operate more
efficiently than with a conventional system, since it can run continuously
on full power until the store is hot, and then switch off.

See the FAQ at http://www.diyfaq.org.uk/plumbing/pl...1.html#thermal
for more information.
--
Cheers,
Set Square
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