In an earlier contribution to this discussion,
phillipthorne wrote:

Hi,

I have an old central heating system which needs changes and
improvements and so I would be grateful for some expert advice please.
At present I have a Homeglow fire/back boiler combination system which
feeds an old rectangular indirect tank in the bathroom. There is only
one pump for the three radiators which it also feeds and the hot water
tank appears to heat from conduction only. With the combined header
tank in the bathroom, at two feet above the sink and bath taps, means
that ground floor user's gets priority for hot water.

My ideal is to eventually do away with the fire/back boiler
combination and to put a condensing boiler outside in the lean-to
section of the house. An on-demand system seems ideal but advice, or
pointers to information, on this would be appreciated. I'm not sure
of the benefits between different systems at present to make any kind
of informed judgement.

Right now I have to move the existing tank into the loft so that I can
update the bathroom and so I need to install something which will fit
in with my future plans of moving the heating source to the outside
location.

Ideally I'd like to do something at this point in time which didn't
involve having to have two water tanks in the loft as I've seen
heating cylinders which look to be completely self contained and
highly efficient.

By sighting a new hot water cylinder directly above where the present
one is then I can simply extend the existing piping up into the loft
and through adding pumps and valves I can make things much more
efficient and suitable for the house. Basically I need a two stage
plan that will allow me to expand and improve the existing system but
which will hopefully contribute components to an eventual ideal
system.

All comments and advice grateful received and thanks in advance
Kind regards and best wishes
Phillip

I'm not quite sure what your ultimate aim is - except for having a new
boiler in a different location. You mention an "on demand" system - which
suggests that you have a combi boiler in mind. If a combi would meet your
requirements, you wouldn't need any stored hot water - so any new tanks in
the attic would be wasted. Combis are ok for small houses with single
bathrooms, where you're more likely to shower than bath, and when you don't
mind the bath taking a long time to fill. But they are only viable if you
have a good mains water supply, capable of delivering at least 20 litres per
minute at the tap nearest to the stopcock. Under all other circumstances,
some means of storing hot water for instant use is higher preferable.

Do you really need to get rid of everything from the bathroom? If you could
accommodate a new, more efficient circular hot tank there, with a header
tank in the attic, you would greatly improve the hot flow in the bathroom.
You really need to pump the HW circuit too, rather than relying on gravity
(convection) to heat it. Do you have a separate small header tank for the
primary circuit? If not, you've probably got a primatic tank where a single
header does both jobs - which isn't particularly desirable and, among other
things, prevents the use of corrosion inhibitor. So you'll need two tanks in
the attic - a big one (50 gallons) as a header tank for the hot water
system, and a small one (5 gallons) as the fill and expansion tank for the
primary circuit. [When you replace the boiler, you'll almost certainly have
a pressurised/unvented primary circuit, and won't need a F&E tank - but your
existing boiler almost certainly wouldn't like that. If your current boiler
*is* ok with an unvented system, you could go to that striaght away and do
away with the need for a F&E tank.]

Before putting *any* water tanks in the attic, make sure that you can
support them adequately - water is heavy stuff! If your ceiling joists are
only designed to support the ceiling, they won't like being asked to support
several hundredweight of water - so you'll need to locate the tanks
somewhere where they're directly supported by a load-bearing wall.

If you have a good cold mains supply, but don't fancy a combi, you might
consider a heat bank. With that, you maintain a tank of hot water at a high
temperature, and use it to heat mains pressure cold water by passing it
through a heat exchanger on the way to the hot taps. You could potentially
put your heat bank in the attic provided it is supported properly. [It's
also possible to have mains pressure hot cylinders - but they need
specialist installation and maintenance, and should probably be avoided.]

These are a few ideas anyway - come back with your own thoughts/reactions.
--
Cheers,
Set Square
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