"Ed Sirett" wrote in message
news
On Fri, 13 Aug 2004 13:05:40 +0100, Ian Calderbank wrote:
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,
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.....
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.
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), boiler capable of running either way, I have no
strong preference, any pros/cons in each direction?
one interesting point between the two is the temp requirement for the
stored water. 60 degrees in unvented, 75 degrees in the heatbank. 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? But I do like the sound of not having all that pressure stuff
to worry about....
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....
Take a look at the sealed CH system FAQ. It may well be better to heat the
heat bank indirectly from a sealed system. The heat bank water itself
beeing a simple F+E header tank.
Pressurised thermal store/heat banks are available. These have the sealed
primary flow and return from the boiler directly connected to the cylinder.
They are basically grade 1 cylinders which are rated at 2.5 bar working
pressure and a test pressure 1 bar above that. When used as a thermal
store/heat bank connected to the boiler they operate at approx 1.5 bar
working pressure and a blow valve of 3 bar, so well within range. The makers
tend to stipulate that the thermal store/heat bank has its own blow off
valve as well as the boiler.
I would rather go with one of these than a thermal store/heat bank using a
an intermediate primary heating coil.