"Christian McArdle" wrote in message
. net...
3. Better heat stratification (runs cold suddenly instead of going
tepid for a while)

Not so. Heat banks can have the same stratification as an other
cylinder.

That isn't my experience. As expected, the flow through the heat exchanger
causes tepid water to enter the bottom at a rate greater than the energy
is
withdrawn.

I have a Gledhill which varies the pump speed to suit the hot water draw-off
temp of 55C. High flow when more taps are on and faster pump speed to
maintain the 55C. Not a problem. No blending valve or flow switch is
required.

This does lead to destratification as the same water cycles round
and a much slower rundown from high to low temperature. This can be
overcome
by slightly oversizing, which isn't much of an issue due to the fact that
the energy storage is higher to begin with due to high store temperature.
It
is also mitigated as a TMV is used on the output, so the output
temperature
is steady until the heat bank water drops quite a lot of temperature.

Have a flow switch on the pipe to the heavy hot water users (bath and
shower) when this switches in it brings in the boiler irrespective of what
the cylinder thermostats want. Use blending valve on the flow-/return and
only 75-80C water enters the cylinder, ensuring the hottest water at the
top.

5. Will provide hot water during power failure (won't reheat, though)

So will a heat bank. A simple immersion is al that is needed in the
cylinder.

Probably didn't explain properly. I meant during an electrical power
failure, not the failure of the boiler.

That is the same for just about everything in heating, unless you have an
electricless multi-point.

P.S. Some of your list assumes a direct type connection to the boiler,
rather than indirect coil. Some of the benefits are lost when an indirect
system is used.

Not to great extent, no. Using a quick recovery coil the length of the
stores cylinder will alleviate that.

However, the indirect system has substantial advantages,
such as being able to use most modern boilers, which frequently require a
sealed pressurised primary system, and being able to place the boiler
above
the level of the cylinder.

That is so. But some top of the range boilers can be open vented and
connected directly.

You can also keep the circulating water separate,
which enables one part of the system to be
drained down, with the other part
still in use, saving down time and the cost of replacing inhibitor
unnecessarily.

That is a very minor point and can be rectified by using simple isolation
valves.



---
--

Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.542 / Virus Database: 336 - Release Date: 18/11/2003