I know the old problem of noisy CH systems has been drawn out time and
time agin on here but i have read most of the other threads and have
tried most of the solutions to no avail.
PROBLEM
I have a vented ch system which seems to get air in it every few weeks
thus its quiet noisy . I have flushed, cleaned and inhibited the system
twice now .I tried some of the helpfull tips like turning the pumps
down and ensuring the header ball cock wasn't stuck , checked for leaks
,etc etc.
I now seem to have introduced another problem or it may have always
been there, now i have turned down the pump speed my boiler seems to be
kettling pretty bad, if i turn the speed up the kettling stops but the
noise from the air ingress starts to occurr again.
Is my only solution to replace the boiler , i have tried turning the
boiler to its low (it only has LO, off, high) setting but the output
isn't sufficient for the cold snaps wew are having.

any advice.


please

On the flow side of the boiler the first T which is the vent pipe tends to be in a negative pressure zone (because the pump is drawing on that area) so air cannot escape up the open vent. The trick is to make this T out of one pipe size larger, the sudden expansion of the water at that point allows the air to release. If yours is a 22mm T get a 28mm T put in. Kettling is quite normal on cast iron boilers, even from new.

On Fri, 25 Feb 2005 13:22:23 -0800, pompeysprk wrote:

I know the old problem of noisy CH systems has been drawn out time and
time agin on here but i have read most of the other threads and have
tried most of the solutions to no avail.
PROBLEM
I have a vented ch system which seems to get air in it every few weeks
thus its quiet noisy . I have flushed, cleaned and inhibited the system
twice now .I tried some of the helpfull tips like turning the pumps
down and ensuring the header ball cock wasn't stuck , checked for leaks
,etc etc.
I now seem to have introduced another problem or it may have always
been there, now i have turned down the pump speed my boiler seems to be
kettling pretty bad, if i turn the speed up the kettling stops but the
noise from the air ingress starts to occurr again.
Is my only solution to replace the boiler , i have tried turning the
boiler to its low (it only has LO, off, high) setting but the output
isn't sufficient for the cold snaps wew are having.

any advice.


Please describe the exact arrangement of boiler, pump, vent and feed
pipework. It may be that you simply have a system that is
wrongly/marginally installed.

More or less the only good way for the pipes to be installed is.

The boiler flow pipe goes to vent pipe always upward and in 22mm.
The the flow is teed from the vent pipe and very near by has the feed pipe
from the header tank teed into it. Then comes the pump.

Such an arrangement has the system pressure under at least the same
positive pressure as it is when stopped. Barring a blockage between
the vent and feed pipe won't pump over.

Older system with cast iron boilers may have the feed and vent pipes
either side of the boiler and the pump pushing water into the boiler.
This can lead to a negative pressure in the highest radiators and the
induction of air into the circuit.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html