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Discuss TBSE on a very long radiator in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

I have a 225cm wide, 45cm high radiator on a standard vented, 8mm microbore two-pipe, fully pumped system.
I am getting rid of its old twin entry radiator valve to install a trv, so I need to decide where to position it and the lockshield.
Easiest option would be TBSE (top-bottom, same end) on the left side of the radiator, with a bleeding valve on the top right corner of the radiator.
However, intuitively, I imagine that with such a long radiator, even if the circuit is pumped, hot water could have a hard time getting from the left end to the right end of the radiator if both valves are on the left end.

Does this make sense, or TBSE will work nevertheless?



if you do it top in on one side and out bottom other side thats the best way,
or in one side bottom out other side bottom, but not as good,
hope that helps.


Agree with the dip tube idea. TBSE works well enough with radiators with large bore (1.5"+) waterways (such as the old British cast iron or European cast aluminium radiators), but they are usually taller than their width, which also helps.

I have experimented with TBSE on horizontal pressed steel radiators and found that, with a wide radiator, the last few inches only got reasonably warm instead of hot - and the radiator I tried it on was only around 150cm wide, so I do think you'd be pushing it without a dip tube.

If you give it a go without the dip tube, I'd love to know the result. It may be that your 225 wide radiator will be no worse than my 150 wide one. What sort of radiator is it, out of interest?
Thanks everyone for the very useful input.
I can confirm now that the previous setup with the twin entry had a very long inner dipping tube, which I extracted, along with the twin entry.

This seems too complicated, so I think I'll switch now, also taking your comments into account, to a TBOE, with an external pipe running below or behind the radiator (sorry, @Ric2013 !).
(I cannot do a BBOE because I haven't been able to undo the relevant nut on the radiator)
Would you think that could work?

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