Rad piping

[TheOldFellow]

The official way of measuring the heat output of a rad is with piping: Top to Bottom same end (TBSE).

But is this the best way? I know that BBOE has a derating factor, so I assume that is not so good (although I can't see why, unless it's cold top corners).

I'm about to fit a new rad, it can be piped up any way really, as the pipework will be from behind the wall.

My inclination is TBOE, but I'd like to understand the physics. TBSE for a long rad seems like imbecility as the flow will be in one end.

R.

[RobertL]

TBOE (with flow to the top) does not rely on internal convenction - the water flows everywhere just by being pumped through it. The other methods do rely on internal convenction which means that the rad cannot all be at the flow temperature. TBOE means you can either run it hot all over for maximum output, or you can run it at lower power (lower flow rate) and minimise the return temperature for the given output (good for efficient use of condensiong boilers). Other methods give a return temperature that is higher (for the same flo temp and power otuput) so are less efficient with a combi.

Also with TBs you can convenientls have a drain plug at the bottom and a vent at the top in the 'unused' tappings - not possible with BB . Robert

[YAPH]

Bzzzzt - combi != condensing!

[Andrew Gabriel]

The only important thing is that the return must be from the bottom. When you have flow at the bottom too, you can easily feel that it rises straight to the top by convection in the first 1 or 2 channels, and most of the radiator then behaves as though flow was at the top.