19 Jun 2019
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United Kingdom
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?

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Depending on the radiator design you might be able to get an injector valve in but 2250 is a long lump to thread in...
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You say that, but BS EN442 requires rads to be tested using TBSE. It, allegedly, gives 2% more output compared to BBOE.
That's interesting.
However, I understand such standard was enforced only around 2013: is that correct?
My radiator probably predates that (by a lot?), hence I wouldn't risk with TBSE.

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