central heating not working after new radiators fitted

[pinkllama]

hi all,

i have just replaced 2 radiators with larger ones in my flat as it took hours to heat the flat up.

it's an open system, ie there is a header tank in the loft.

i refilled the system and bled all the radiators.

the problem now is that the boiler fires up for a few minutes and then switches off - not heating any of the radiators. i've put the thermostat on max. the header tank has water in it.

prior to fitting the new radiators, it worked fine.

i understand that the boiler is switching itself off as a safety measure as it is too hot.

i think that there could be an air lock in the boiler that is preventing it from working/ pumping the water around the radiators. when i turn the boiler on, it sounds 'hollow' as if there is no water in it.

its currently -5c outside and i desperately need some help!!

are there any other places, apart from the radiators that should be bled of air?

regarding bleeding the pump, i took the chrome nut off the front when the system had been refilled, but couldn't see how to bleed it. there is a large plastic turnable slit on the right hand side, is this where you bleed it?

one thing that could be a clue as to why it's not working is, when i refilled the system the header tank let loads of water in for a few seconds then it just trickled in for the next hour or so before all the radiators were full of water.


any advice?

thanks

 

[jackthom]

Is there a motorised valve in the system? This should be manually opened when refilling.

The large chrome screw on the front of the pump is the one for bleeding, when loosened there should be air or water dribbling out.

The slow filling is worrying. It's possible that sludge in the header tank has gone down into the system and partially blocked the cold feed inlet pipe.
Is there a compression fitting anywhere near the bottom of this pipe that can be opened to check the cold water flow into the system and perhaps flush it through if necessary?

 

[dextrous]

Turn it in, and while the pump is running, undo the screw to bleed it - check that the pump is turning. The other "turntable" thing is to adjust the speed.

 

[pinkllama]

Is there a motorised valve in the system? This should be manually opened when refilling.

The large chrome screw on the front of the pump is the one for bleeding, when loosened there should be air or water dribbling out.

The slow filling is worrying. It's possible that sludge in the header tank has gone down into the system and partially blocked the cold feed inlet pipe.
Is there a compression fitting anywhere near the bottom of this pipe that can be opened to check the cold water flow into the system and perhaps flush it through if necessary?

the motorized valve was closed. i've now opened it.

i can't see any compression fitting on the inlet pipe.

is it a good idea to bleed the 2 rads that aren't working, of some water. hoping that air will eventually come out?

 

[dextrous]

yes - bleed everything possible.

Also, what make/model or boiler have you got, since these sometimes need priming too!

 

[pinkllama]

yes - bleed everything possible.

Also, what make/model or boiler have you got, since these sometimes need priming too!

it's a baxi WM282 RS