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In message , Set Square
) wrote:

Run it at the lowest speed which gives an adequate performance. With
a
conventional boiler, this would imply an 11 degC drop across all
radiators
when they are correctly balanced.

Maybe I'm being thick, but that looks to me as if it implies:

- in parallel rad systems, output per rad proportional to rad size,
when that's not necessarily whats wanted, its defniitely not in this
house at least.

- in older series plumbed rad setups, very little heat output from
rads on the end of the chain in small houses, or no heat at all in
large houses.

Maybe someone can explain?

NT

In an earlier contribution to this discussion,
N. Thornton wrote:

In message , Set Square
) wrote:

Run it at the lowest speed which gives an adequate performance. With
a conventional boiler, this would imply an 11 degC drop across all
radiators when they are correctly balanced.

Maybe I'm being thick, but that looks to me as if it implies:

- in parallel rad systems, output per rad proportional to rad size,
when that's not necessarily whats wanted, its defniitely not in this
house at least.

The philosophy of having a uniform drop does assume - maybe
optimistically(!) - that the system has been designed with the correct size
of radiator in each room to balance the heat losses of the room. If you have
any seriously over-sized radiators, you need to restrict the flow a bit more
so as to reduce the average temperature. [If you've got any seriously
under-sized rads, you're stuffed!]

- in older series plumbed rad setups, very little heat output from
rads on the end of the chain in small houses, or no heat at all in
large houses.

Maybe someone can explain?

Are you talking about single pipe systems - where the water flows through
all the radiators in series rather than parallel? If so, there are hopefully
not too many of these still around - and the normal balancing rules wouldn't
work.

Here, each radiator is receiving water which has already been through all
the upstream radiators, rather than direct from the boiler. The average
temperature of each radiator is thus lower than that of its predecessors -
so you need progressively larger radiators if you are to get any decent heat
out of them.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

The message
from (N. Thornton) contains these words:

Run it at the lowest speed which gives an adequate performance. With
a conventional boiler, this would imply an 11 degC drop across all
radiators when they are correctly balanced.

Maybe I'm being thick, but that looks to me as if it implies:

- in parallel rad systems, output per rad proportional to rad size,
when that's not necessarily whats wanted, its defniitely not in this
house at least.

The design output of radiators is quoted with that sort of temperature
drop. ISTM that with balanced rads you will get the same proportion of
the rated heat output from each rad even when circumstances mean that
you won't get the actual rated heat output. Should you have a badly
designed system (ie some radiators that don't match the heat demands of
the room) you need some other means of regulation as well such as TRVs.

- in older series plumbed rad setups, very little heat output from
rads on the end of the chain in small houses, or no heat at all in
large houses.

Single pipe systems are little better than ornament. When the heating is
needed the most the radiators at the end of the chain have the least
chance of any significant temperature drop.

--
Roger

On 26 Dec 2004 07:14:17 -0800, (N. Thornton) wrote:

In message , Set Square
) wrote:

Run it at the lowest speed which gives an adequate performance. With
a
conventional boiler, this would imply an 11 degC drop across all
radiators when they are correctly balanced.

Maybe I'm being thick, but that looks to me as if it implies:

- in parallel rad systems, output per rad proportional to rad size,
when that's not necessarily whats wanted, its defniitely not in this
house at least.

Yes. In practice it is very difficult to achieve perfect balance,
BUT, the alternative is one radiator gets very hot and loads are very
cold so even a rough balance is better. TRVs will do the final
balancing. A rough balance is still needed though since otherwise the
morning warm up will not be even.

--

Malcolm

Malcolm Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
, or ).
Design Service for Analogue/Digital H/W & S/W Railway Signalling and Power
electronics. More details plus freeware, Win95/98 DUN and Pspice tips, see:

http://www.fullcircuit.com or http://www.fullcircuit.co.uk

NEW - www.CharteredConsultant.co.uk - The Consultant A-List

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