"Ian Calderbank" ian_calderbank at dont-spam-me.hotmail.com wrote in
message ...
On Thu, 12 Aug 2004 12:56:18 +0100, "IMM" wrote:

Go for a heat bank. The local plumbers fit megaflows because they know
no
different. A heat bank requires an electrical connection so they shy
away.
A Megaflow requires you to service it each year to reinstate the air
pocket
(PITA). They require large 1" copper overflows too. If there is a burst
the
insurance will not pay up.

Get a heat bank with a solar coil already in the bottom, ready for
connection. Also have the CH fed from the heat bank too. Then solar
heated
water will supply the CH as well as DHW.
Most makers will supply a "integrated" (CH & DHW) heat bank.
http://www.heatweb.com
http://www.range-cylinders.co.uk (go thermal storage)
Contact the makers and they will identify a model for you. DPS make heat
banks that don't require an overflow.

If these plumbers say heat banks are no good they are not worth employing
as
they don't know their stuff. They are superior to unvented cylinders in
most
points, and especially when you are incorporating solar panels.

Scale? Fit a phosphor de-scaler, available from, B&Q and the lies for
around £45-50, on all the water except the kitchen drinking tap and
garden
hose. A heat bank can be DIY descaled by removing the plate heat
exchanger.
Make sure they incorporate full bore isolation valves either side of the
plate to remove the plate heat exchanger without a drain down and re-fill
which can be expensive as they require about 3 bottles of inhibitor.

well, I've spoken to Range and DPS,
interestingly I got opposing stories....

range talked about both but preferred to
recommend unvented cylinder
(tribune) as this can come with dual coils
as standard, saying service
requirement was simply a matter of a
pressure check with a car-tyre
pressure gauge, and a test of the relief
valve you can do yourself,

Still a service. If you did it yourself and there was a burst, would the
insurance company pay up? I doubt it,as they will find any excuse not to
pay.

vs flowmax with a 2nd coil would be
a special build and in their
opinion not as well suited to providing
the volumes needed for a large
house, more designed for new-build
smaller homes, and also not so good
for hard water area.....

Range are big and want to sell off the shelf stock. Their FloMax is geared
towards smaller homes.

An unvented cylinder will not use solar heated water for CH, it is only used
for DHW. Scale? "Always" fit a phosphor scale reducer in any hard water
area on any system.

DPS on the other hand straightaway
suggested their heatbank, and it
certainly seems to eliminate a lot
of the pressure/temperature relief
requirements of the unvented.

It eliminates all of it as it is at low pressure

With the heatbank, the option for
heating the store itself is direct
onto the CH circuit or indirect via
coil, the difference being whether
the CH system is sealed(=indirect)
or unsealed (=direct), at the
moment its unsealed (good old feed-expansion
tank in the loft which I want rid of but there
is room for one in the airing cupboard along
with a big cylinder),

Heat banks come mainly wit the F&E tank integrated with the cylinder.

boiler capable of running either
way, I have no strong preference,
any pros/cons in each direction?

With a direct heat bank keep it the open vented. the heat bank provides the
CH F&E tank.

one interesting point between
the two is the temp requirement for the
stored water. 60 degrees in unvented,
75 degrees in the heatbank.

The heat bank uses the hot water to instantly heat the incoming cold mains
water. the unvented cylinder is the water you use at the taps. the water in
a heat bank is primary water.

So I would guess that as a possible solar
input also has to heat-exchange
into the tank, the lower temp would
be easier to make use of that
energy?

Having a solar coil at the bottom of a heat bank will heat the water in the
cylinder. Fully in summer, not so much in winter. In winter it may only be
tow temp, but it is being used to preheat the cylinder, it all counts and it
is used for CH and DHW.

But I do like the sound of not having
all that pressure stuff to worry about....

If you have ever seen they aftermath of an exploded unvented cylinder you
would shy away. Total devastation.

neither had any suggestions about who
to use for system design/install
other than IOP listed (which I am
trying to stick with anyway). So I
guess I will just have to wave the names
under peoples noses and see
what reaction I get....

A heat bank can have all the controls, pumps etc all on the cyinder, DPS
would do this for you. All yu do is connect up the relevant wires and pipes.
The flow and return of the CH circuit is connected up to the CH tappings.
The DHW is a matter of cold in hot out pipes, and the boiler is a matter of
connecting up the boiler flow and return to the heat bank. Simple stuff, no
real design work for an dumb installer to do, and the experts who design the
heat bank do virtually all of it for you.

A heat bank eliminates inefficient boiler cycling, which an unvented
cylinder will not. Eventually I would replace that cast iron boiler.
Modern "heating" condensing boilers are far more efficient.

If you want to replace it now then consider a Powermax or Gledhill
Gulfstream 2000, which incorporate incondesning boilers. An all in one
solution. The 2000 is available from Travis Perkins plumbing dept.

http://www.powermax.co.uk
http://www.gledhill.net