Baniging with Hot Water (stops if C/H turned on) !!!!!!

[slackjawgaze]

I have a potterton profile 50 el wall mounted boiler.

Installed about 6 months ago.

3 bed semi - pump in room above boiler - 9 radiators in house - conventional boiler. Set to number 3 1/2(6 is max).

When the hot water comes on only (water timed/heating off) after about 5 -10 mins - extremely loud banging pipes !!!!!! sounds like the whole world is about to blowup.....

If i turn on the central heating this stops the explosions.

I have bled all radiators - no air escaping/all rads hot top and bottom.

ANY IDEAS - what is wrong ? i guess air in system somehow can anyone please help.....

PS How can i tell if my system is gravity fed?/sealed or open vented?

 

[B.O.B DOLE]

I have a potterton profile 50 el wall mounted boiler.

Installed about 6 months ago.

3 bed semi - pump in room above boiler - 9 radiators in house - conventional boiler. Set to number 3 1/2(6 is max).

When the hot water comes on only (water timed/heating off) after about 5 -10 mins - extremely loud banging pipes !!!!!! sounds like the whole world is about to blowup.....

If i turn on the central heating this stops the explosions.

I have bled all radiators - no air escaping/all rads hot top and bottom.

ANY IDEAS - what is wrong ? i guess air in system somehow can anyone please help.....

PS How can i tell if my system is gravity fed?/sealed or open vented?

where abouts is the banging
sounds as tho there is an air lock on the cylinder

 

[slackjawgaze]

the banging comes from the pipes above the boiler (in the room above) that go away to the imersion tank 2 rooms away on the top floor.