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?

wrote in message
...
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?

It will vary - describe the range of "shooting up and down"

On Feb 10, 2:01*pm, "John" wrote:
wrote in message

...

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?

It will vary - describe the range of "shooting up and down"


I fill the boiler to approx 1.25 bar. Once the heat comes on, the
pressure shoots up to 3 bar. Once the heat comes off it settles back.
While the boiler continues to operate, the pressure will drop slowly
to 0 and then I have to top-up again.

All very painful when i have to get up at 5am to top up...

thanks for your quick response

wrote in message
...
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?


Is is a combi boiler or do you have a separate DHW tank?

If the latter there could be a leak of primary water from the tank coil into
your hot water system.

On Feb 10, 2:32*pm, "Vortex4" wrote:
wrote in message

...

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?

Is is a combi boiler or do you have a separate DHW tank?

If the latter there could be a leak of primary water from the tank coil into
your hot water system.

Its a combi, Potterton Puma 80 boiler.

wrote in message
...
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...

It could be that there's not *enough* air in your expansion vessel. If it
has a diaphragm you won't see water coming out the air top up valve unless
the diaphragm has failed. If there is too little air then the expansion
vessel might not have enough capacity to absorb the water expansion in the
system.

Tim

Any ideas?

"Tim Downie" wrote in message
...

wrote in message
...
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...

It could be that there's not *enough* air in your expansion vessel. If it
has a diaphragm you won't see water coming out the air top up valve unless
the diaphragm has failed. If there is too little air then the expansion
vessel might not have enough capacity to absorb the water expansion in the
system.

Tim

Any ideas?


Good point.

Release the system pressure and check the "precharge" at the valve on the
pressure vessel.

IIRC this should measure at about 1-1.5 bar when there is no system
pressure. If it's too low pump it up with a foot pump.

On 10 Feb, 13:58, "
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?

Blocked connection pipe between the expansion vessel and the system.
Ideal Classic combis were a bugger for blocking where the connection
flex tees off the boiler internal pipes. Many others with small bore
connections blocked within the small bore section.
HTH

John

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
_______
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

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
_______
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

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?

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
_______
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

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.