On Wednesday, 28 October 2020 13:21:10 UTC, Dave Liquorice wrote:

Yeah, a lot depends on the history. Including has the system ever
been replaced in the past? Radiator sizing in the late 60's would
have been for flow/return temps of 75/65 C or there abouts, rather
than the 65/55 flow/return that a condensing boiler likes so it runs
in condensing mode.

and target temps were lower, eg 13C in bedrooms.

It's not impossible to just add another rad or upgrade the occasional one, but the condition of rads & pipes is at best unknown. It might be blocked beyond hope.


NT