"Andy Hall" wrote in message
...

Provided that the cylinder is large enough,
which takes us back to the
point that it is only as good as the
energy stored plus the energy
that can be delivered into the heatbank
from the boiler while the
former is delivering energy to the
heat exchanger.

No. The system acts like a combi as a fall back.

Sure, but the performance level will have dropped off.

The point is you "never" run out of hot water.
Your hot water is 2 stage of high flow and
then low flow.

That's fine if you find that type of
performance acceptable.

Just about everyone with common sense would find it acceptable. You have
enough high flow water, then if you do run out of high flow your fallback to
a low flow. Never run out.

I would prefer to see the cylinder
adequately sized regardless of
whether it is used in a conventional
way or as a heatbank.

What makes you think it would not provide enough hot water?

No. With a beat bank the boilers output goes straight to the DHW draw
off.
This is not the case with a vented or unvented cylinder.

No it doesn't. With a vented or unvented cylinder, the boiler energy
is fed through a coil in the cylinder to heat the DHW in the cylinder.
A heatbank can be indirect or direct. In the indirect case, the
boiler heats a coil in the cylinder in the same way, but the water is
then pumped through a stainless steel heat exchanger to heat the DHW.
In the direct case the cylinder water passes through the boiler but
is still used via the stainless steel heat exchanger to heat the DHW.

failed!

The only real difference is that in the
heatbank case you have stored 25%
more energy in a given volume or a
small reduction in space.

You don't understand.

I understand perfectly, thanks.

You don't. failed!

Yes, and unvented cylinders do not have very large coils.

That depends on what you order and from whom.

Again.. unvented cylinders do not have very large coils.

Rubbish. If you order one with a substantial coil, you get one with a
substantial coil. That's exactly what I did. I had the
manufacturer install a pocket for a temperature probe and extra
fittings as well.

Coils in unvented cylinder are never as large as vented because if a large
boiler heated up the cylinder from cold it would create too much pressure in
the cylinder and the pressure relief controls would cut in. The Telford
Tornado is "trickle" charged.



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