I've recently had the central heating switched off due to a nail through a radiator pipe (long story for another day). But since bleeding the system and resetting the boiler I've had trouble getting any heat in the radiators. I think I've identified that what seems to be a pressure relief tap (thats t'd in after the pump and joins to the cold return from the radiators) that must've been left open by the plumber when he drained the system?
Am I right to think therefore the hot water from the boiler was taking the path of least resistence through this open tap and effectively being pumped straight back to the boiler? and as a result putting pressure on both ends of the radiator circuit hence no flow through them?
I've turned this tap off (and since opened it a little) and immediately the flow has returned to the radiators.
My concern now is that the radiators seem to be too hot (i've turned down the TRVs but recognise this isn't the answer) and I've turned down the boiler to the temperature it was previously at before the work was done.
Should this pressure relief tap be opened further and does that reduce the heat? Am I doing the right thing? Not being an expert I'm not sure if I've done the right thing by closing the tap up, and I'm not sure if my theory above is even correct, it just seems logical.
Any advice on how to reduce the radiator heat (given I've got TRVs) and to correctly set/balance this pressure relief tap (assuming thats what it is!).