On Tuesday, December 12, 2017 at 9:33:08 AM UTC, Roger Hayter wrote:
Brian Gaff wrote:

Surely with a longer pipe run more water in the system equals more expansion
and contraction, so the brain, though a little rusty might suggest raising
that pipe to accommodate the expansion?

Brian

Surely the tank accommodates the expansion, and the height of the
overflow just accommodates the pressure differential due to the pump?

--

Roger Hayter

Hmmmm,

Some interesting comments. SOME of the new rads are actually replacements (in new positions) for old rads which have been removed), but overall, yes, there is more water in the heating circuit, so perhaps that is the issue as Brian suggests.

How to solve it? I'm not yet sure. As I say, there are plenty of rads still left at the moment without TRVs, so I't's (sadly) not a question of simply fitting a bypass.