As part of some renovations I've just moved a rad. in the living room, some of the 3/4" pipe work for the old rad lead off in the direction of nowhere in particular on taking up a few more floor boards I found it was looping the flow and return, effectively shorting the feed to the rads at about the furthest point in the house from the boiler. Having removed the loop all the rads are suddenly much hotter.
I guess at some time in the past the heating circuit was changed from a loop pipe with convection feed to the rads to a contemporary flow and return system and whoever did it forgot about the loop . . . any other thoughts?