Does thin copper pipework prevent radiators from achieving their rated BTU output?

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Hi – there are actually four questions I’m hoping you can help with – shown at the end of the post.

In my living room even with the radiator on full blast pretty much all the time (and scorching to the touch), the room is never what you’d call cosy. It has one radiator at the door (600mm x 1400mm rated at 8500 BTU). But a plumber once told me that the thin (1cm diameter) copper pipework connecting the radiator would probably mean that the radiator may not even produce the full rated output(?).

The online calculators recommended between 11000 and 17000 BTU. Most were around the 13000 mark. So I realise that even with the perfect pipework, I will still need to significantly increase the BTU output in the room to make it habitable over the winter!

The living room is part of a traditional Glasgow tenement flat. The room is on the second floor south/southwest facing and more exposed to the elements than most. It has 13 square metres of plastic-framed double glazing (fitted 15yrs ago), two outside walls and a heated room above and below it. It’s not unduly droughty, but obviously it breathes more than a newer property would. The dimensions are roughly 4m wide by 6m long with 3.7m ceiling.

I want to replace the radiator with the highest output radiator possible. I’d prefer not to extend beyond 1400mm width, but could easily increase height from 600mm to 700mm if that would make a worthwhile difference.

The highest output I could find in these sizes was the Ultraheat Ultimate High Output High BTU range – their 600mm x 1400mm Type 22 DF Double (double panel, double convector) is rated at 11200 BTU, with the 700mm x 1400mm model rated at 12587 BTU (see https://www.ultraheatradiators.com/...heat Radiators Ultimate High Output High BTUs)

I could also rip up floors and add a second radiator to one other wall. However, I’d prefer not to as my sofa backs onto that wall and I’d end up with a new radiator sitting just a couple of inches away from the back of my sofa (there’s nowhere else I could put the sofa). Plus within reason I’m trying to fix the problem with the minimum mess/disruption)

My questions are:

1) Do you know of a brand/range of radiators that gives a higher BTU output than the Ultraheat Ultimate High Output BTU range shown in the link above?

2) Roughly how big a reduction in BTU output does 1cm diameter copper piping cause? Is it likely to be a big reduction or fairly minimal?

3) Is there any advantage to biting the bullet and extending to a wider radiator so that even if the radiator doesn’t achieve its rated output due to the 1cm diameter copper piping, the reduced output is still (hopefully) at least 11000 BTU? (eg. the Ultraheat 700mm x 1800mm is rated at 16184 BTU)

4) Would having a second radiator sitting within a few inches of the back of a sofa be a waste of time – or would this actually be a better way to provide the extra output needed than increasing the current radiator beyond 1400mm width?

Thanks in advance for your help!
 
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My cousins radiators are 8 mm microbore .He got his changed to 15mm and he also changed some of his radiators from single to doubles. And now his house is boiling. But make sure if changing radiators that your boiler can handle the upgraded btu rating. or your house won't achieve the heat you want and your ch will work overtime . Im looking to do this to hopefully before winter . Replace my microbore with 15 mm and some rads
 
if the radiator is getting hot, and it's still not hot enough in the room, that would suggest you need a bigger radiator
8mm microbore is what you seem to have, and it should be capable of heating a bigger rad, however it will take longer to heat up as there's more water in it.
an additinal rad would help heat your room up, especially if it's a big space, however to do this you would need to run the pipework from it back to the main manifold which is most likely in the middle of the house, (only 1 rad can run off one microbore supply) you could pipe this one in 15mm
i've worked in many tenements in Glasgow and the rooms with huge high ceilings with little insulation are murder to heat up, i think you might be better off with 2 rads in that room,

also, ive never heard of microbore causing a reduced output in radiators, they just take longer to heat up
 
I would be very dubious about the claimed outputs of Ultraheat Radiators. 8000 BTU for a 600 x 1000 Type 22, compared to to 6067 BTU for a same size Stelrad Elite is too good to be true. The fact that they do not publish technical details does not help.
 
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I know this doesn't answer any of your questions, but I've heard that when rad manufacturers do their measurements they use TBSE (Top Bottom Same End) connections, i.e. both flow (at Top) and return (at Bottom) on the left or both on the right.
If you throw TBSE at a search engine and then spend some time I'm sure you'll find some details about how this gives greater output.
Cheers, Graham
 
I know this doesn't answer any of your questions, but I've heard that when rad manufacturers do their measurements they use TBSE (Top Bottom Same End) connections, i.e. both flow (at Top) and return (at Bottom) on the left or both on the right.
If you throw TBSE at a search engine and then spend some time I'm sure you'll find some details about how this gives greater output.
Cheers, Graham
That's correct, but the improvement is only 1-2%, not 33%!!
 
Wow thanks for all your replies and expertise!

G1zm0 – If I can get 15mm without having to do too much floor lifting then that’s a possibility. Nearly all the radiators are already doubles. I’m confident the boiler can cope with the extra BTU – it’s a Vokera Unica 36HE (Central Heating Output is 108,565 BTU) in a flat with five rooms plus a small hallway. This was far bigger than the Vokera Linea 24 it replaced and more than a normal flat of this size should need. I was actually forced to upgrade the boiler because the replacement combi-powered shower I had installed 3yrs ago point blank wouldn’t provide a decent temperature at anything other than a dribble of pressure. Pity – the old combi-powered shower worked just fine off the Vokera 24 Linea – that was one expensive shower let me tell you!

Gasmanstu72 – I’ve also been told that 10mm will only supply up to around 1.5kw of heat (around 5000 BTU). I don’t mind if the larger replacement radiator takes a while to heat up – as long as it gets there eventually, which I think you are saying it will! Agreed, though – perhaps best to have two radiators. Yeah – tenements are terrible to heat – my next house will be a newbuild with low ceilings and bog standard sizes for everything lol!

D_Hailsham – yes I did wonder as I know Stelrad is considered to be top notch. After your post, I did find some info online suggesting that BTU and kW ratings are calculated by the manufacturers using different Delta-T values. Those who show the older Delta-T60 regulation BTU and KW will show as inflated compared with those showing the newer Delta-T50 regulation. So for example, the site in the link below uses Delta-T50 and rates the Ultraheat 600mm x 1000mm at 6385 BTU (1.869KW). This is pretty close to the 6067 BTU for a same size Stelrad Elite(?). Although as an average homeowner, I have no clue what Deltas-T50 or T60 mean and would be unlikely to understand it even if someone tried to explain it! (http://www.leagrave.net/product/411/ultraheat_600hx1000l_double_radiator/)

Boringoldcodger – every increase helps so I will definitely ask my heating engineer/plumber to check this when he visits!

Again, thanks for sharing your thoughts and experience as I’m really keen to fix this once and fix it right – winter’s approaching and it’s already getting chilly at night..!
 
Boringoldcodger said "throw TBSE at a search engine".
Whoops, I've found out that throwing:
TBOE radiator connection
is a better idea. From that I got link:
https://books.google.co.uk/books?id...#v=onepage&q=tboe radiator connection&f=false
If (understandably) that link doesn't work, then the entry 3 or 4 pages into google which talks about Faber and Kell's... is the one.
That says that moving from BBOE (probably the usual UK connection) to TBSE can give an increase in the range of 19% (0.16 increase starting from 0.84) to 28% (0.22 increase starting from 0.78).
Cheers, Graham
 
TBSE Is top/bottom at same end, not very efficient way to heat a rad, sure it wasn't TBOE was the best way?
 
Another consideration is what temp is your central heating set at at the boiler?

Many rad outputs are quoted at 80*c flow so you need to run em hot to get the stated outputs,

Micro bore does have its limits, think from memory practically it's about 4kw.
 
That says that moving from BBOE (probably the usual UK connection) to TBSE can give an increase in the range of 19% (0.16 increase starting from 0.84) to 28% (0.22 increase starting from 0.78).
Stelrad's Stars Program says there is no difference betwenn TBSE and TBOE, while BBOE gives only a 2% reduction. I have never seen such large improvements suggested as you have quoted.
 

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