In an earlier contribution to this discussion,
Stephen wrote:

Hello,

I was asking about radiators on the "CH pipe size" thread but the
discussion has moved on to radiator sizes rather than pipe sizes, so I
thought a new thread would be useful.

I just wanted to ask two last questions:

Is 300W a noticeable difference in heat output: I have found two
radiators for sale and their outputs differ by 300W, would I notice
the difference?

It depends on what percentage change this represents! You'd be more likely
to notice the difference between 300 and 600 than between 2300 and 2600.

Is there a big difference between makes on panel radiator regarding
their outputs? Sorry to switch units but I was looking for a rad about
7000BTU and I see some makes I can use a 500x1300, others require
500x1400 and others 500x1600. Different makes of 500x1400 have
different outputs (hence question one above).


To at least a first order of approximation, all radiators of a given size
and construction should give the same output under the same (Delta-T)
operating conditions. The output depends on:
* surface area of the panels and fins
* emmissivity of the surface finish
* mean surface temperature

None of those things are going vary all that much from make to make. There
may be slight variations depending on the spacing and depth of the fins -
which could have an effect on the amount of convected heat entering the
room.

There are rules of thumb for watts per square metre for each basic type -
single panel without fins, single panel with fins, double panel without
fins, double panel with single fins, double panel with double fins, etc.
Most manufacturers' published data fit in with the rules of thumb fairly
well - although some manufacturers do quote different outputs for different
shapes[1] even though the areas may be the same.

Are you sure that all the examples which you cite are specified at the same
dT?

[1] e.g. 2000 x 300 vs 1000 x 600
--
Cheers,
Roger
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