"DIYSOS" wrote in message
...
In a post a few days ago, off-topic I mentioned (in Jest!) using an old
23KW
gas multipoint water heater to heat a thermal store for a new CH system.
It
ended with me thinking I'd ditch the multipoint to make way for the
cylinder. Err, well... see below.
First, a question relating to thermal stores. To promote a cool return
temperature I'm contemplating that I may (or may not!) need to run my
1300mm/210L store at a lower temperature - say 70 degr rather than 80. To
compensate, I was going to get Newarkcyl to add one or two alternative
tappings a bit higher up the cyl for the space heating take-off. But I'm
working blind, I don't have the foggiest what the existing return
temperatures will be, or where to ask for the extra holes to be. Any
ideas?
And one other thing, what is the difference between a 'vented' CH boiler
and
a multipoint - both just heat water don't they (:-).
I just couln't let go of the idea of a free (installed) CH boiler. There
*will* be a thermal store - the only issue now is what & where the boiler
will be. If the council don't object on Part L (It's an existing boiler)
then I'll hook up the multipoint. I now plan to put the store on the
ground
floor, under the stairs in the middle of the house. The primary pipes will
run to the multipoint boiler along a path that will run close to the
(ground
floor) siting of any new Condenser boiler - if and when that happens. F&E
tanks in the loft. Pumps near to the store (maybe).
At the moment I'm now planning on doing it as Dr Evil suggested -
integrated
with common primary water to boiler, store and radiators. There might be
risk of the Fernoxified, sludgy brown water affecting the multipoit's
rubbery flow sensors? but I'll take a chance. And as the store is now
downstairs, in the event of a catastrophic leak upstairs at least the
cylinder contents wouldn't add to the flood.
One thing that occurred to me is that the water in the multipoint would
generally be hotter than if heating from the cold mains. And as the
pressure
via the F&E will be relatively low this might risk 'kettling"? For this
reason I'd like the return temperature to the boiler to be cool. On the
other hand, if fitting a condensing boiler (now or in future) then again
I'd
like the ruturn temperature to be cool to promote condensing. So, I've
gone
for a somewhat oversized 1300mm, 210L thermal store, Newarkcyl, to aid
'stratification'. Two stats as well - external as these give positioning
flexibility.
And if the above is completely mad let me know!.
Thanks DIYSOS.
If you want a lower store temperature go for a larger store, as you are
doing, but have a plate heat exchanger for DHW take off. These are so
efficient they can run with a thermal store at 60-65C.
You are wanting the store below the boiler position and below the highest CH
rad. This will mean two coils in the store. One for CH and one for the
boiler. Both boiler and CH circuits will need to be pressurised. A system
boiler comes complete with vessel. A separate vessel is needed for the CH
circuit. The store needs is own F&E tank. Look at:
http://www.rangecylinders.co.uk/prod..._combi/index.h
tml
They can install another coil for you. Have two stats on the cylinder to
prevent boiler cycling. Or get a cheaper quote for a defined spec.
To use the multi-point with the store, a temporary measure by you I believe.
You will need a temporary F&E tank for the boiler flow and return primaries.
Run the primaries in 28mm. Have the pump on the boiler return to apply
pressure to lift the diaphragm. Have a clamp on pipe stat on the boiler
flow set to 80C, this cuts off the pump when 80C is reached. This will
prevent boiler temperature overshoot. Have the cold feed from the F&E
between the pump and boiler and the open vent teed off the flow pipe.
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