Airlock in CH system, but all radiators are working?!

[lister01]

Hi there. Three weeks ago we had a new pump fitted in our (conventional) boiler. Now the central heating sounds like it's possessed. Whenever it comes on there's a period of about ten minutes where it sounds like the pipes are going to pull apart; clanking, clanging, whooshing, HUGE crashes and bumps from various places in the walls and ceiling...

It seems obvious there's air in the system, but all of the radiators are working - at least I think they are, they're hot all the way to the top which implies there's no air pocket in them.

I have an additional problem in that a few of the rads are so old no keys fit them and I can't even loosen the entire valve at the top because they don't seem to have one; just an indent and a tiny peg which doesn't fit any key.

How do I get this air out of the system? Any help greatly appreciated!

 

[footprints]

Call back the guy that fitted the pump it the first thought.
It might be set too high for the system and pulling in air on start up, but anyway he is the chap to call.

 

[MikeAustin]

Call back the guy that fitted the pump it the first thought.
It might be set too high for the system and pulling in air on start up, but anyway he is the chap to call.

Where would the pump pull air from - and where would the pump put it afterwards?

 

[denso13]

Where would the pump pull air from

The open vent?

and where would the pump put it afterwards?

No idea, does it matter?

 

[MikeAustin]

Where would the pump pull air from

The open vent?

and where would the pump put it afterwards?

No idea, does it matter?

You mean the vent on the pump, not the vent pipe? The reason I ask is because I have similar problems. Air is already in the system - I don't know how - and when the pump starts, this air is compressed and water from the F&E pipe is drawn in because it has somewhere to go. When the pump stops, it all rushes back again. All very noisey! My pump is brand new and self-venting, so I am baffled.

 

[denso13]

You mean the vent on the pump, not the vent pipe?

I do mean the vent pipe (open vent). On a sound system with no leaks it is the only place air could be drawn in.

 

[MikeAustin]

You mean the vent on the pump, not the vent pipe?

I do mean the vent pipe (open vent). On a sound system with no leaks it is the only place air could be drawn in.

So, the F&E pipe would have to be blocked (because this keeps the vent pipe level the same as the F&E tank level) or the F&E tank is empty? These are the places lister01 should be looking?

 

[denso13]

So, the F&E pipe would have to be blocked

Doesn't need to be blocked. It may be the system design but none of us has seen the OP's system.

As footprints said earlier it sounds although it is linked to the new pump installation and that is where I'd be looking first.

 

[MikeAustin]

So, the F&E pipe would have to be blocked

Doesn't need to be blocked. It may be the system design but none of us has seen the OP's system.

As footprints said earlier it sounds although it is linked to the new pump installation and that is where I'd be looking first.

If the system was working OK before, I would guess everything is where it should be. And if the pump is a straight swap (and it is not faulty), then the problem would be with refilling and bleeding the system. The answer to this problem would also be of use to me.

 

[denso13]

Or new pump set too high as mentioned previously.

 

[gigz]

Did the pump installer drain the system down ? Or just close the pump valves ?

 

[MikeAustin]

Did the pump installer drain the system down ? Or just close the pump valves ?

Good point. On my system, there is the F&E and vent on one side and a bleed vent the other side, so air pockets are unlikely to get very far. Apart from that, my pump has a 10 minute venting session after installation.