Install radiator pipes top/bottom or both at bottom?

[kevplumb]

never heard of flexible

not that you needed it when it was done

the tube went straight down the bottom header

 

[doitall]

Would that be inside a double panel or outside.

 

[kevplumb]

try cast and get offa your high horse smartass

 

[doitall]

 

[D_Hailsham]

Cheers geez.

Reading through that, I noticed a couple of things.
Apart from the odd 2%, the MWT for steamers would be 15 k lower than the 90-70 used here. At an average of 2% per K, that would lower the advertised output using the old standard by about 30%.
Makes calculating to the watt accurate (let alone btu) a bit of a joke.

The maths is a bit harder than 2% per K. Try this one:

Untitled

• D_Hailsham
• 12 May 2009
• 3

Its used to calculate the rad output factor table you find in manufacturers' literature.

t1 = flow temp
t2 = return temp
tr = room temp
ln is the natural logarithm (base e); Newton's law of cooling is responsible for that.
"n" is a coefficient which depends on the type and height of radiator and is about 1.3. Stelrad publish n-coefficients for their Elite range.

Don't ask me where the 49.33 comes from, I don't know. In any case, I have seen other figures used, e.g 49.83.

 

[bengasman]

Don't ask me where the 49.33 comes from, I don't know. In any case, I have seen other figures used, e.g 49.83.

It maybe a bit more accurate, but the heatloss calculation contains a total of up to 20% in allowances if I remember correctly, and my figure of 30% will not be far off.
Even if it is far less than I think, it is still 20 + 20, and never allowing for drafty doors and windows.
I think I will stick with my own less scientific system: quick look around, compare with another thousand rooms I have seen; K2 1400 x 600 will do nicely.

"By the way mr Punter, I tend to oversize the rads quite a bit so you could save a a score by using a smaller one, but it will take a lot longer to warm up nicely and if it is really cold, it might not be enough."

Have yet to find the first client who wants to save the 20 squid.

Radiator calculations are really a thing from the past.
Oversize them a fair bit, the room will heat up quicker, and the boiler will condense better. When it is warm enough, the electronics will turn the whole lot off so it actually works out cheaper to run.