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?

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).

Thanks in advance.
Stephen.

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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On Thu, 6 Aug 2009 10:19:40 +0100, "Roger Mills"
wrote:

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.

Very true! I shall have to calculate the percentage difference.

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)

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.

That's what I thought, which is why I was surprised that the outputs
differed. Perhaps some marketing departments "tweak" their figures
more than others?

I am currently looking at a Quinn Barlo 500x1400 double (2.3kW, 7900
BTU IIRC). Is Quinn barlo a good make? I think it's the least I can
do, since Barlo were kind enough to provide the calculator

I have looked at other makes 500mm high and double width to produce
the same output; one required 500x1600 but another managed with just
500x1300. I am surprised that 160mm in one outputs as much as 1300mm
in another; I would have thought a foot difference in length would
have made a big difference to output.

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

Yes, after all your previous help with factors, I checked, double
checked and checked again! Only Toolstation and 4bathrooms quote
dT=60, everyone else is using dT=50

Thanks again.
Stephen.

On 6 Aug, 11:35, Stephen wrote:
On Thu, 6 Aug 2009 10:19:40 +0100, "Roger Mills"

wrote:
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.

Very true! I shall have to calculate the percentage difference.

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)
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.

That's what I thought, which is why I was surprised that the outputs
differed. Perhaps some marketing departments "tweak" their figures
more than others?

I am currently looking at a Quinn Barlo 500x1400 double (2.3kW, 7900
BTU IIRC). Is Quinn barlo a good make? I think it's the least I can
do, since Barlo were kind enough to provide the calculator

Quinn Barlo are good, we have had one of their radiators for 6 years,
very well made and solid.


I have looked at other makes 500mm high and double width to produce
the same output; one required 500x1600 but another managed with just
500x1300. I am surprised that 160mm in one outputs as much as 1300mm
in another; I would have thought a foot difference in length would
have made a big difference to output.

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

Yes, after all your previous help with factors, I checked, double
checked and checked again! Only Toolstation and 4bathrooms quote
dT=60, everyone else is using dT=50

Thanks again.
Stephen.

In an earlier contribution to this discussion,
Stephen wrote:


I am currently looking at a Quinn Barlo 500x1400 double (2.3kW, 7900
BTU IIRC). Is Quinn barlo a good make? I think it's the least I can
do, since Barlo were kind enough to provide the calculator

I have looked at other makes 500mm high and double width to produce
the same output; one required 500x1600 but another managed with just
500x1300. I am surprised that 160mm in one outputs as much as 1300mm
in another; I would have thought a foot difference in length would
have made a big difference to output.


Would you care to define "double"? Some doubles have *two* sets of fins -
back to back on both panels - (K2 in Stelrad parlance) and some have just
one set (P+) - and it makes quite a difference to the output. Just looking
at a Stelrad data sheet, a 1200 x 450 K2 has a very similar output to a 1600
x 450 P+.

Are you sure that you're comparing apples with apples?
--
Cheers,
Roger
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In an earlier contribution to this discussion,
David wrote:


I am currently looking at a Quinn Barlo 500x1400 double (2.3kW, 7900
BTU IIRC). Is Quinn barlo a good make? I think it's the least I can
do, since Barlo were kind enough to provide the calculator

Quinn Barlo are good, we have had one of their radiators for 6 years,
very well made and solid.

I'm sure they're as good as anyone else's. I tend to regard radiators as a
'commodity' purchase - they're all much of a muchness - so unless you're
prepared to pay through the nose for a pretty looking 'designer' jobby, go
for the cheapest. Whatever you go for, there are some good on-line deals
which are a lot cheaper than anything you'll get at the sheds.
--
Cheers,
Roger
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On 6 Aug, 16:46, "Roger Mills" wrote:
In an earlier contribution to this discussion,

David *wrote:

I am currently looking at a Quinn Barlo 500x1400 double (2.3kW, 7900
BTU IIRC). Is Quinn barlo a good make? I think it's the least I can
do, since Barlo were kind enough to provide the calculator

Quinn Barlo are good, we have had one of their radiators for 6 years,
very well made and solid.

I'm sure they're as good as anyone else's. I tend to regard radiators as a
'commodity' purchase - they're all much of a muchness - so unless you're
prepared to pay through the nose for a pretty looking 'designer' jobby, go
for the cheapest. Whatever you go for, there are some good on-line deals
which are a lot cheaper than anything you'll get at the sheds.
--
Cheers,
Roger
______
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The Altech ones from Graham are poorly made.

On Thu, 6 Aug 2009 16:46:02 +0100, "Roger Mills"
wrote:

I tend to regard radiators as a
'commodity' purchase - they're all much of a muchness - so unless you're
prepared to pay through the nose for a pretty looking 'designer' jobby, go
for the cheapest.

Thanks. That's what I thought, as I said in an earlier post, the
standard panel; ones all look the same to me.

The ones I had looked at were all double radiators with double fins
and all 500mm high.

The web sites all list output in BTUs, I have divided by 3.413 to
calculate the Watts.

Kudox (at B&Q) 500m x 1400mm has a 7053 BTU (2.07kW) at dt=50
Quinn 500 x 1400 is 7941 BTU (2.33 kW)
Myson 500 x 1400 is 7094 BTU (2.08 kW)

I cannot understand why the Quinn is so much higher than the other
two.

The Biasi from 4 bathrooms is the only one rated at dT=60. At dT=60
the output is 8505, which by my calculations (divide by 1.27) equates
to 6697 BTU (1.96 kW), which seems a little lower than the others.
Why?

Whatever you go for, there are some good on-line deals
which are a lot cheaper than anything you'll get at the sheds.

Any offer/merchant you recommend in particular?

Thanks again.
Stephen.

Sorry, I should have added that the Barlo calculator says I need 2.2kW
or 7473 BTUs, so this is why I am anxious about the outputs of the
rads. The Kudox and Myson would be below this but the Quinn would be
ideal for my requirements. However, is the rating for the Quinn too
good to be true? I could buy a 1600mm rad just to be sure, but I would
like to keep the length and cost of the rad as small as possible!

Thanks.

In an earlier contribution to this discussion,
Stephen wrote:


The ones I had looked at were all double radiators with double fins
and all 500mm high.

The web sites all list output in BTUs, I have divided by 3.413 to
calculate the Watts.

Kudox (at B&Q) 500m x 1400mm has a 7053 BTU (2.07kW) at dt=50
Quinn 500 x 1400 is 7941 BTU (2.33 kW)
Myson 500 x 1400 is 7094 BTU (2.08 kW)

I cannot understand why the Quinn is so much higher than the other
two.


No, nor can I! Would you care to provide URLs for each of the 3 sites?



Whatever you go for, there are some good on-line deals
which are a lot cheaper than anything you'll get at the sheds.

Any offer/merchant you recommend in particular?

The last time I bought a radiator (about a year ago), I got it from
http://www.theheatingshop.co.uk/ They were very competitive at the time.
They took a few days to deliver 'cos they don't hold any stock, but use
local merchants. [I think it was delivered to me by the local branch of
PlumbCenter - but at a much lower price than if I had gone direct to them.]

I've also had a few from Screwfix - but they only do (or did) a limited
range of sizes. ISTR that they didn't do any that were more than 600mm tall,
and I wanted some at 700.
--
Cheers,
Roger
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On Thu, 06 Aug 2009 09:10:09 +0100, Stephen wrote:

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).

suggest you check the article on radiators in the wiki - it has a formula
for working out the output of any standard rad given its sizes and
configuration



--
John Stumbles -- http://yaph.co.uk

"I used to think correlation implied causation.
Then I took a statistics course and now I don't."
"Sounds as if the statistics course helped."
"Well, maybe."

On 6 Aug 2009 19:13:28 GMT, YAPH wrote:

suggest you check the article on radiators in the wiki - it has a formula
for working out the output of any standard rad given its sizes and
configuration

But that was my question. If all radiators that are the same height,
same width, and all double finned, why should one make have a higher
output. If they are all constructed the same and obey the same
formula, should all outputs be equal?

On Thu, 6 Aug 2009 19:49:35 +0100, "Roger Mills"
wrote:

No, nor can I! Would you care to provide URLs for each of the 3 sites?

Here you go:

Kudox (at B&Q) 500m x 1400mm has a 7053 BTU (2.07kW) at dt=50

http://www.diy.com/diy/jsp/bq/nav.js...mm&x=2 8&y=14


Quinn 500 x 1400 is 7941 BTU (2.33 kW)

http://www.discountedheating.co.uk/s...m_High_K2.html


Myson 500 x 1400 is 7094 BTU (2.08 kW)

http://www.discountedheating.co.uk/s...mm_High.h tml

I cannot understand why the Quinn is so much higher than the other
two.

The Biasi from 4 bathrooms is the only one rated at dT=60. At dT=60
the output is 8505, which by my calculations (divide by 1.27) equates
to 6697 BTU (1.96 kW), which seems a little lower than the others.

http://www.4bathrooms.co.uk/store/pr...278&bestseller

Stephen wrote:
On 6 Aug 2009 19:13:28 GMT, YAPH wrote:

suggest you check the article on radiators in the wiki - it has a formula
for working out the output of any standard rad given its sizes and
configuration

But that was my question. If all radiators that are the same height,
same width, and all double finned, why should one make have a higher
output. If they are all constructed the same and obey the same
formula, should all outputs be equal?

The heat output of a radiator is also critically dependent on its
working temperature and the ambient temperature. So the same rad can
have many different outputs depending on how its measured.

If it was red hot, it would output a fair but more..

In an earlier contribution to this discussion,
The Natural Philosopher wrote:

Stephen wrote:
On 6 Aug 2009 19:13:28 GMT, YAPH wrote:

suggest you check the article on radiators in the wiki - it has a
formula for working out the output of any standard rad given its
sizes and configuration

But that was my question. If all radiators that are the same height,
same width, and all double finned, why should one make have a higher
output. If they are all constructed the same and obey the same
formula, should all outputs be equal?

The heat output of a radiator is also critically dependent on its
working temperature and the ambient temperature. So the same rad can
have many different outputs depending on how its measured.

If it was red hot, it would output a fair but more..

Yes, we *know* that - but manufactuers' published data should surely all be
based on measurements made under the *same* operating conditions - certainly
when they quote the same delta-T.
--
Cheers,
Roger
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monitored.. Messages sent to it may not be read for several weeks.
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In an earlier contribution to this discussion,
Stephen wrote:

On Thu, 6 Aug 2009 19:49:35 +0100, "Roger Mills"
wrote:

No, nor can I! Would you care to provide URLs for each of the 3
sites?

Here you go:

Kudox (at B&Q) 500m x 1400mm has a 7053 BTU (2.07kW) at dt=50

http://www.diy.com/diy/jsp/bq/nav.js...mm&x=2 8&y=14


Quinn 500 x 1400 is 7941 BTU (2.33 kW)

http://www.discountedheating.co.uk/s...m_High_K2.html


Myson 500 x 1400 is 7094 BTU (2.08 kW)

http://www.discountedheating.co.uk/s...mm_High.h tml

I cannot understand why the Quinn is so much higher than the other
two.


Thanks for the URL's. I'm afraid they don't reveal any obvious reasons for
the differences.

My own rules of thumb would give a figure of 2000 watts at dT=50 (or 2500
watts at dT=60) for that size of radiator - which stacks up quite well with
2 of the 3 offerings. My immediate thoughts were that the Quinn/Barlo one
may have been measured at 60 even though they claimed 50 - but that would
take it to 2500 instead of 2350. I suppose they *could* have measured it at
55 - that would be closer, but still not quite right.

In any event, I would be inclined to suspect the Quinn figures. Unless
they've found a clever way of defeating the laws of physics, their design is
unlikely to be 15% better than everyone else's.
--
Cheers,
Roger
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On Fri, 7 Aug 2009 11:26:14 +0100, "Roger Mills"
wrote:

I would be inclined to suspect the Quinn figures. Unless
they've found a clever way of defeating the laws of physics, their design is
unlikely to be 15% better than everyone else's.

From Quinn: "I can confirm that the output is correct this is due to
our design of the vertical water channels being at a market leading
pitch of 25mm combining our convection fin configuration gives us a
high performing radiator."

I may still go for the 1600mm, just to be sure.

One last question: I have been using the Barlo calculator to calculate
the radiators I need. I am unsure what to do about the hall. Aren't
hall, stairs, and landing all one thing? Heat from the radiator at the
foot of the stairs will rise. How do I go about entering ceiling
heights and wall lengths to get a suitably sized radiator (there is
no radiator on the landing). Thanks.

In an earlier contribution to this discussion,
Stephen wrote:

One last question: I have been using the Barlo calculator to calculate
the radiators I need. I am unsure what to do about the hall. Aren't
hall, stairs, and landing all one thing? Heat from the radiator at the
foot of the stairs will rise. How do I go about entering ceiling
heights and wall lengths to get a suitably sized radiator (there is
no radiator on the landing). Thanks.

You need to do it as several bits - just as you would an L-shaped room - and
add them together. So you'll have a downstairs bit, an upstairs bit and a
two-storey bit where the stairs are. Obviously where two bits meet in fresh
air, you need to create a 'wall' which has a U value of zero - but the
temperature will be the same on both 'sides', so it doesn't really matter.
--
Cheers,
Roger
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On Wed, 12 Aug 2009 12:49:54 +0100, "Roger Mills"
wrote:

You need to do it as several bits - just as you would an L-shaped room - and
add them together. So you'll have a downstairs bit, an upstairs bit and a
two-storey bit where the stairs are. Obviously where two bits meet in fresh
air, you need to create a 'wall' which has a U value of zero - but the
temperature will be the same on both 'sides', so it doesn't really matter.


That's what I thought but I wanted to double check: I am doing the
right thing by specifying the hall radiator to heat all of the hall,
stairs, and landing?

The stair section will be triangular because at the bottom of the
stairs the height is two storeys but at the top it is only one. What
is the best way around this? Use a measurement of half the base x the
height?

I had a look at the heatingshop url you gave but their web site is
confusing; it would be easier if you didn't have to add supplements
depending if you bought a single, double, or one and a half size
radiator.

BTW did you see the reply from Quinn; what did you think?

Thanks again.

In an earlier contribution to this discussion,
Stephen wrote:

On Wed, 12 Aug 2009 12:49:54 +0100, "Roger Mills"
wrote:

You need to do it as several bits - just as you would an L-shaped
room - and add them together. So you'll have a downstairs bit, an
upstairs bit and a two-storey bit where the stairs are. Obviously
where two bits meet in fresh air, you need to create a 'wall' which
has a U value of zero - but the temperature will be the same on both
'sides', so it doesn't really matter.


That's what I thought but I wanted to double check: I am doing the
right thing by specifying the hall radiator to heat all of the hall,
stairs, and landing?

Yes.

The stair section will be triangular because at the bottom of the
stairs the height is two storeys but at the top it is only one. What
is the best way around this? Use a measurement of half the base x the
height?

It's not an exact science - don't worry too much! Just imagine the
rectangular 2-storey space you would have if you removed the staircase, and
regard that as one 'room'. Then treat what's left of the ground floor hall
as another 'room' and what's left of the first floor landing as a third
room - and add all 3 heat losses together.

I had a look at the heatingshop url you gave but their web site is
confusing; it would be easier if you didn't have to add supplements
depending if you bought a single, double, or one and a half size
radiator.

I don't remember anything like that when I bought from them - but mine was
only a single-panel finned rad. Can you give an example of what you mean by
pointing to a particular page on their site?

BTW did you see the reply from Quinn; what did you think?


It stretched my credulity a little!
--
Cheers,
Roger
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On Wed, 12 Aug 2009 22:28:57 +0100, "Roger Mills"
wrote:

I don't remember anything like that when I bought from them - but mine was
only a single-panel finned rad. Can you give an example of what you mean by
pointing to a particular page on their site?

Hello again,

I got that slightly wrong. Some web sites have a separate page for
singles, doubles, and "one and a half"s but the heating shop just
lists them all together by size:

http://www.theheatingshop.co.uk/scpr...n%20Convectors

I was thinking of another web site, I can't remember which now, but it
too listed all rads by size, gave the price for the single and then
said "an extra £xx" for the P+, and extra £yy for the double, which
wasn't straightforward.

A local merchant is offering "ultraheat" radiators; has anyone heard
of them; are they any good?

Thanks again,
Stephen.

On Wed, 12 Aug 2009 22:28:57 +0100, "Roger Mills"
wrote:

BTW did you see the reply from Quinn; what did you think?

It stretched my credulity a little!

If I understood it correctly, they were saying that the "ribs" in the
radiator were closer together? If so would it give off more heat
either because of an increased surface area or because it holds more
water?

I have now been offered an ultraheat 500x1400 quoted at 7743 BTU at
dT=50, which also seems higher than the others, though not as high as
the Quinn.

So to be safe I will buy a 1600mm length in whatever make is cheapest!

I can't understand how these manufacturers get different results
because I thought they had to be tested in standard rooms?

In an earlier contribution to this discussion,
Stephen wrote:


If I understood it correctly, they were saying that the "ribs" in the
radiator were closer together? If so would it give off more heat
either because of an increased surface area or because it holds more
water?


If you increase the surface area, you will increase the heat output
(provided you pump more water through it to compensate) - which is why a rad
with fins has a higher output (by about 50%) than a rad without.

But fins is fins and I'd expect all rads of the same basic construction to
be much of a muchness. Fin spacing will have an effect - so my hunch is that
a spread of perhaps 5% would be reasonable but that 15% would be pushing it.

I could be wrong, of course!
--
Cheers,
Roger
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On Fri, 14 Aug 2009 11:12:21 +0100, "Roger Mills"
wrote:

But fins is fins and I'd expect all rads of the same basic construction to
be much of a muchness. Fin spacing will have an effect - so my hunch is that
a spread of perhaps 5% would be reasonable but that 15% would be pushing it.

Thanks for your patience in this thread. Sorry it has taken me so long
to choose a radiator! It's a good job it's not winter or we would have
frozen by now! I'm thinking of getting a Stelrad now because they are
450mm tall rather than 500mm and I think 500mm would be too close to
the curtain. What is the recommended space between curtain and
radiator?

Thanks again.

On Fri, 14 Aug 2009 19:35:08 +0100, Stephen wrote:

On Fri, 14 Aug 2009 11:12:21 +0100, "Roger Mills"
wrote:

But fins is fins and I'd expect all rads of the same basic construction to
be much of a muchness. Fin spacing will have an effect - so my hunch is that
a spread of perhaps 5% would be reasonable but that 15% would be pushing it.

Thanks for your patience in this thread. Sorry it has taken me so long
to choose a radiator! It's a good job it's not winter or we would have
frozen by now! I'm thinking of getting a Stelrad now because they are
450mm tall rather than 500mm and I think 500mm would be too close to
the curtain. What is the recommended space between curtain and
radiator?

Thanks again.

I hope a negative figure, as my curtains tuck down the back of the
radiator!
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

Stephen wrote:
On Fri, 14 Aug 2009 11:12:21 +0100, "Roger Mills"
wrote:

But fins is fins and I'd expect all rads of the same basic
construction to be much of a muchness. Fin spacing will have an
effect - so my hunch is that a spread of perhaps 5% would be
reasonable but that 15% would be pushing it.

Thanks for your patience in this thread. Sorry it has taken me so long
to choose a radiator! It's a good job it's not winter or we would have
frozen by now! I'm thinking of getting a Stelrad now because they are
450mm tall rather than 500mm and I think 500mm would be too close to
the curtain. What is the recommended space between curtain and
radiator?


Upstairs, we have sufficient clearance between the top of the rads and the
window cills for me to have installed veneered contiboard shelves to deflect
the heat into the rooms when the curtains are closed.

Downstairs we have one window where the only solution was to have a curtain
of sufficient length to tuck behind the rad.