air in how wter/heating system

[mondial]

I have a potterton boiler and a small tank in the loft, in addition to the hot water tank which is upstairs. When the boiler lights up (set on a timer) there is almost continous noise of air bubbling through the pies, for the first 30 minutes. I have bled all radiators but air is in the water system, not the rads. HELP!

 

[meldrew's_mate]

Check the header tank is re-filling on its ballcock, else give some more details and history. Has the pump been changed recently? Try turning the speed down, does this help? Does it pump on the flow or return?

Raises more questions than answers at this stage, doesn't it

 

[mmalone]

Check the header tank is re-filling on its ballcock, else give some more details and history. Has the pump been changed recently? Try turning the speed down, does this help? Does it pump on the flow or return?




Raises more questions than answers at this stage, doesn't it

system may also be corroded, if you need to keep bleeding rads its cause there no inhibiter in the system, wont cure the problem to add it but will help a lot and limit corrosion, had this problem in my last house, I flushed the system added sludge remover, drained 2 weeks later then added inhibitor and it deffo helped a lot !! make sure it aint pumping over also as advised above !

 

[Nige F]

Check the header tank is re-filling on its ballcock, else give some more details and history. Has the pump been changed recently? Try turning the speed down, does this help? Does it pump on the flow or return?

Raises more questions than answers at this stage, doesn't it

I DON`T BELIEVE it, m8

 

[mondial]

I'm sorry. I tried to be brief and failed to give all relevant information, so here goes.
I live in a two storey flat with a 16 year old central heating system. a potterton ideal neterheat, 8 radiators (four up and four down), a hot water tank in the airing cupboard with a grundfos pump, running at full speed. In the loft is a header(?) tank.
The ball valve appears to work perfectly with 4 inches of water in the tank. The 4 upstairs radiators heat up along with two of the downstairs ones. Two downstairs furthest from the boiler and pump do not work unless we close off two upstairs ones, when they heat up. There is no air in the radiators, just clean water.
The major problem is the noise of air in the pipes which is very loud and happens every time the system is turned on by the timer, twice a day. This noise is almost continuous for 30 minutes.
I have bled the pump with the big central screw. In the airing cupboard, between the hot water tank and the pump is a bleed screw, which lets out a little air when undone.
Any help would be appreciated.

 

[mondial]

Sorry, forgot to say that the advent of the noice coincides with the fitting of a new three way valve, about a year ago.