Bleeding!! central heating system

[syedraza]

I had to drain off the system today so that I could change a radiator valve (downstairs) as it was leaking. When I refilled the system up, the hot water is back on in the taps, and the radiators upstairs are hot, but none of the radiators downstairs are hot. the central heating system pump seems to be working as it is hot and i can feel and hear water passing through it. what could be wrong and what do i need to do to get them to work?

I have bled each of the radiators until all the hissing went away and water came out.

I have a Grundfos central heating pump. 15-50 if that means anything. I dont know much about pumps, but looking at it there is a screw infront of it, probably the size of a one penny piece. If i have bled all the radiators, can I belled this pump too? If so how? I have heard that you can give the pump a sharp knock to try and dislodge any thing, if this safe and if so how do i do this?

 

[ianniann]

Pumps can sometimes need bleeding and it sounds like this one has a bleed screw. Hopefully someone will confirm or you can track down a manual.

 

[Andygasman2010]

Sounds like an air lock, not necessarily in the pump. Turn off all the upstairs radiators for a while, that should shift it.

 

[syedraza]

Thanks for that.

I tried that already. I closed off all the upstairs radiators for about half an hour and only one of the downstairs ones came on. then after a while that wnet off too.

 

[Andygasman2010]

What boiler/system do you have? Where's the pump and components? Where's the cold-feed?

 

[syedraza]

Hi,

Right I have retried what you mention in the last message. I have closed off the upstairs radiators, and turned off the water too. one of the downstairs radiators seems to be getting warm. I will wiat for this to fully warm up and then turn that one off too. is this right? should the other two remaining ones turn on too after that?

As for your next question, I have a water tank for the central heating system, so I imagine this is whats called an open system. is it? the pump is in a little area upstairs next to the bathroom. it it is also the hot water cylinder. the cold feed is in the loft.

 

[Andygasman2010]

Sounds like it's just air locked. Persistance is the key!