On 11 Feb, 20:18, "
wrote:
On Feb 10, 10:43*pm, "Roger Mills" wrote:





In an earlier contribution to this discussion,

wrote:
hi there
I have a pressure prob with a sealed gfch system.

The pressure shoots up and down - according to the FAQ, this prob
means that the expansion chamber has failed, but when I check the
chamber, there is no water coming out of the valve - only air. Air
pressure is approx 10/11 PSI. I keep topping up water, but there is no
apparent leak...

Any ideas?

Under what conditions did you measure the air pressure? It needs to be done
when the water system is *not* pressurised.

The water is almost certainly being lost through the pressure relief valve,
which opens at 3bar. You need to find where this discharges to the outside
world, and hang a container under the pipe to see how much water you
collect.

As others have said, the problem is probably just that there's insufficient
charge pressure (air) in the expansion vessel. This needs to be pumped up to
about 10 PSI (0.7 bar) when there's no pressure in the water system, and
then you need to use the filling loop to pressurise the water system to
about 1 bar (cold).
--
Cheers,
Roger
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Ok thanks for all that.

From what I can tell having a closer look, the auto air vent is
unwell. The little red knob was tight, when I loosen it, it started
leakin.... in the absence of anything obvious wrong with the expansion
vessel, I will take a gander at that first. Even when sealed tight,
could this be the cause of the problm?- Hide quoted text -

- Show quoted text -

No
If it has a red cap on the auto air vent its probable that it also has
a fibre washer. the idea with those was to let the air out until the
float inside shut the outlet then close the cap. Subsequent
accumulation of air would allow the fibre to dry out and air to escape
then if water followed the fibre would expand and shut the escape to
liquid. The fact that water was behind the cap does not suggest a
system problem.
There were even some auto air outlets that only used fibre washers and
no float valve.
Your problem is either as others have said with your expansion vessel
precharge or as I said the connection to the expansion vessel is
blocked.