Air in CH System

[sknight]

I am having a problem with my Boiler. Potterton Kinfisher2. Gravity fed system with 1 pump on return pipework next to boiler.
The system is making lots of noise as if there is air in the system. The system has been drained down and cleaned with X200. Inhibitor has been added.
When the boiler come on in the morning there seems to be a gugling and whooshing noise as if there is massive movement of air in the pipwork. (this only lasts for about 3-4 secs) The system then starts to warm up and there are lost of what I can only describe as tiny bubbles streaming past the Rad valve every minute or so.
One the heating is nearing temp the boiler starts to make banging noises as if the air is going into the boiler and causing hot spots.

If I stop and start the pump when hot I hear no major gurgling noises, If I increase the pump speed I sometimes can get more bubble noises from the system.

All the Rads are getting hot and circulation seems good to be very quick.

When draining and refilling the system I have ensured that I did it by the book!

I can bleed a little more air out of the system every couple of days, but this does not seem to be enough for the noises being produced.
There are no air bleed valves on the system only the overflow back to the header tank.
The system is only 10 years old and the CH water when drained was very clean.
Can not find any leaks on the system.

Any Ideas?

 

[kevplumb]

did you bleed the pump

 

[sknight]

Yep,
Middle screw removed and bled, didn't get any air out

 

[kevplumb]

have you got a valve in the airing cupboard (3 port) usually there is a vent on the pipework
did you remember to lock it on man while refilling

 

[sknight]

no 3 way valve. The system is gravity fed HW and Pumped CH.
No air bleed.
The only place for air to be released is the rad bleed valve and the overflow to the header tank.
Air should eventually get to this point as the sir should rise, but the is does not seem to be happening

Thanks

 

[kevplumb]

sorry just read your first post again (where you stated gravity )
only other thing that springs to mind is blockage in the vent

 

[sknight]

checked this by blowing down it.
The overflow it T'd iff the head tank feed.
when I blow down the overflow the head tank bubbles, thus there can not be a blockage in the expasnsion overflow.

At some stage I think I will check the system using a glass full of water over the overflow to see if any water gets sucked out of the glass. read this up on the fernox site to check for system leaks.

This is foxing me and keeping me awake!!!!

 

[kevplumb]

ditto and i dont sleep well anyway(ask oilman )

 

[sknight]

Just bled all rads and pump. Opened all lock shield valves and filled header tank a bit more to give some more pressure on the system.
The glass test did nothing.
Off to bed and hopfully will not wake me up in the morning!!