BTU of radiators

Just been comparing the specs of Screwfix/Wickes rads and surprised that the BTUs vary so much for similar sized rads.
Eg:
Wickes single convector, 620 x 1200mm, 3840 BTU Screwfix single convector, 600 x 1200mm, 5838 BTU
Wickes double convector, 620 x 1200mm, 7325 BTU Screwfix double convector, 600 x 1200mm, 10980 BTU
Prices are similar and outputs all measured at DeltaT50.
I'd have thought products at this end of the market would be pretty similar in design/manufacture, so why the big difference in output? Or is 30% not a big difference?
TIA,
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 16 Feb 2004 02:12:52 -0800, snipped-for-privacy@yahoo.com (mike) wrote:

Comparing Screwfix catalogue 73 to 72 (the latter matches the website) suggests their radiators have all systematically leapt in output terms by 50%, yet look identical and are otherwise described no differently. Someone has screwed up, I would say.
--
I believe in free will - my religion says I have no choice.

Mail john rather than nospam...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John Laird wrote:

When I ordered a 600x800 double rad from Screwfix, I used Catalogue 72 and saw that it was a high rating (approx 2kW I think). Compared to the ones at B&Q (3 cheaper with output specs written on the packaging) Screwfix's were a much higher output so went with them.
After ordering I looked at Screwfix's website and noticed that on there the specs were much lower (1.8kW I think), even lower than the one at B&Q. When the radiator was delivered, there was no mention of the specs on it - just the size. I assumed it must have been a printing error in catalogue 72 but in the package was a new 73 catalogue with the same ratings printed in it. So which do we believe - the catalogue or the website? I've had 2 editions of the catalogue now with the same ratings in them without correction. Judging by the specs for other similar sized radiators (of same construction) it appears that Screwfix's website is more believeable than their catalogue.
David
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 16 Feb 2004 10:58:25 -0000, "David Hearn"

The ratings in my copies of catalogue 72 and 73 are definitely not the same. Curious. There are no obvious printing revision numbers anywhere.
--
To Be and Not To Be - Zen Shakespeare.

Mail john rather than nospam...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

I've just thrown away (still in the bin!) a catalogue which says "Vol 72B" on the front. Can't remember whether there was a 72A!
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Set Square wrote:

From what I've seen, the B edition always seems to be the one which "Recommend a friend" on the front and the form to fill in before handing to someone else.
Not sure if they're a corrected edition, or just a different front cover.
David
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for all the replies.
As far as I know the Wickes rads do have fins (the last one I fitted certaily did) and the quoted figures are measured under the same conditions.
I've just checked Screwfix's website and the figures there are very similar to the Wickes figures so, as has been suggested, it seems the catalogue figures are mis-prints.
How do the fins increase the heat output so much? Is it a case of the extra mass of metal conducting more heat from the water and/or the fins setting up convection currents?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I wouldn't buy anything from a supplier that only quotes the figures in BTUs because it leads to mixing of units when calculating what is needed in the rest of the system in terms of capacities, sizes etc. You also end up with funny conversion factors which can lead to arithmetic errors. It is far easier to work entirely in SI units such as metres, grams, watts and degrees C.
Also I would trust the figures given in the data sheets of a branded manufacturer such as Myson, Barlo or Stelrad because it is there main business and they are producing specific data sheets. The implication of errors for them is far more than for a short lifetime catalogue issued by Screwfix or Wickes who could just as easily switch vendors tomorrow afternoon.
If you look at the data sheet of a (for example) Myson radiator you will see that there are versions with and without fins - in fact single and double panel with 0, 1 or 2 sets for a given area. There are big output differences.
These come partly because the surface area is increased and partly because of the encouragement of convection currents.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John Laird wrote:

Or has rated them at 70C water them instead of 60 say?
Or into a room at 5C instead of 20C?
s
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'm getting very confused by all this!
I have a 72B and a 73 catalogue. Both of these and the website ALL quote the single panel 600 x 1200 rad as 3778 BTU.
Where did to OP get the figure of 5838 from?
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

My 73 catalogue says 5838. My 72 catalogue agrees with yours. So now we have reports of both editions containing lower and higher figures ;-)
I'd believe the lower figures every time. Even if the rads were newly sourced, a 50% increase would require some considerably advanced technology. Apart from mirror-imaging the photos, they look identical.
--
I'm an analog man in a digital world.

Mail john rather than nospam...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

From catalogues 73 and 73B, which have identical figures. I've just emailed Screwfix and asked them to confirm that the website figures are the correct ones.....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 16 Feb 2004 02:12:52 -0800, snipped-for-privacy@yahoo.com (mike) wrote:

They're obviously not the same, are you sure you're comparing like for like. Are they both of the K type, i.e. with or without fins. Check the specs again. ..
SJW A.C.S. Ltd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

Are you sure that you're comparing apples with apples? If the Wickes radiators don't have fins on the back whereas the Screwfix ones do, that will make a hell of a difference to the output.
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
E-mailed Screwfix who confirmed the website figures are correct and the catalogue figures wrong.
Replied within 30 minutes too....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.