Expansion vessel in sealed system
 

Can anyone tell me, broadly speaking, what the symptoms of duff one of
these would be? I'm referring to large metal tank, which presumably
has a diaphragm in it, which supposed to be pressurised with air.

By "duff", I mean if the diaphragm is leaking, such that the unit had
no air in it. Other than air in the system, what would be the effect
of having no expansion room. Leaking joints and valves?

Can anyone tell me, broadly speaking, what the symptoms of duff one of
these would be?

When the system heats up, the water expands. The expansion tank should
accommodate this expansion, keeping the pressure rise down below
approximately 0.5 bar.

If the expansion tank is totally blown, there is nowhere for the water to
go. The pressure would rise rapidly, almost certainly operating the pressure
relief valve (normaly at 3 bar or thereabouts). Lots of water would leave
via the outlet.

When the system cools down, there would no longer be enough water to fill
the system and the pressure would drop to zero + the head from the pressure
gauge to the water level. This would require you to refill at the filling
loop.

Sometimes, a system will have 2 expansion vessels. This is often the case
with a large system, when the vessel internal to the boiler is insufficient
to keep the pressure rise below 0.5 bar, so the designer has specified an
additional vessel. In this case, the pressure rise upon heating may be
excessive, but not enough to flow the pressure relief valve, as the working
vessel works overtime.

Christian.

On Mon, 13 Sep 2004 10:00:42 +0000, John Carlyle-Clarke wrote:

Can anyone tell me, broadly speaking, what the symptoms of duff one of
these would be? I'm referring to large metal tank, which presumably
has a diaphragm in it, which supposed to be pressurised with air.

By "duff", I mean if the diaphragm is leaking, such that the unit had
no air in it. Other than air in the system, what would be the effect
of having no expansion room. Leaking joints and valves?

See below.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

"Ed Sirett" wrote in
n.co.uk:

http://www.makewrite.demon.co.uk/SealedCH.html

Great resource! Thanks!

"John Carlyle-Clarke" wrote in message
. 1.69...
"Ed Sirett" wrote in
n.co.uk:

http://www.makewrite.demon.co.uk/SealedCH.html

Great resource! Thanks!

On the first section I saw an error. It says:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

Disappointed, I never went any further after that.

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.

Christian.

"IMM" wrote in message
...

"John Carlyle-Clarke" wrote in message
. 1.69...
"Ed Sirett" wrote in
n.co.uk:

http://www.makewrite.demon.co.uk/SealedCH.html

Great resource! Thanks!

On the first section I saw an error. It says:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

Disappointed, I never went any further after that.





The faq is great. Using it I upgraded to a sealed system with additional
help from the group.

Also different manufacturers of expansion vessels give different locations
for the vessel.

Also, while Googleing I came across Schnellkupplungen for a
Membrandruckausdehnungsgefäß and what is involved is an item that enables
the expansion vessel to be isolated for servicing without draining the whole
system. Some contain a locking cap that is sealed in a similar manner to
electricity and gas meters.

It seems that these conform to regulations in some parts of Europe, don't
know about the UK.

It allows the vessel to be isolated from the system, water drained from
vessel thus allowing the air pressure to be tested.

No doubt this thread will get the xenophobes going again.



Francis

"FrancisJK" wrote in message
...

"IMM" wrote in message
...

"John Carlyle-Clarke" wrote in message
. 1.69...
"Ed Sirett" wrote in
n.co.uk:

http://www.makewrite.demon.co.uk/SealedCH.html

Great resource! Thanks!

On the first section I saw an error. It says:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

Disappointed, I never went any further after that.





The faq is great. Using it I upgraded to a sealed system with additional
help from the group.

Also different manufacturers of expansion vessels give different locations
for the vessel.

Also, while Googleing I came across Schnellkupplungen for a
Membrandruckausdehnungsgefäß and what is involved is an item that enables
the expansion vessel to be isolated for servicing without draining the
whole
system. Some contain a locking cap that is sealed in a similar manner to
electricity and gas meters.

It seems that these conform to regulations in some parts of Europe, don't
know about the UK.

It allows the vessel to be isolated from the system, water drained from
vessel thus allowing the air pressure to be tested.

A full bore valve before the pressure vessel does much the same thing. Turn
off and remove.

"Christian McArdle" wrote in message
. net...
"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.

I know few. if any, systems that do not require an auto air vent above the
boiler on the flow pipe. In days gone by when there was no system boilers
with integral pressure vessels and all components had to be external, an
auto air-vent on the flow over the boiler was mandatory by all
manufacturers. You didn't think, you just put one in.

I know few. if any, systems that do not require an auto air vent above the
boiler on the flow pipe. In days gone by when there was no system boilers
with integral pressure vessels and all components had to be external, an
auto air-vent on the flow over the boiler was mandatory by all
manufacturers. You didn't think, you just put one in.

I'm not saying they're not an excellent idea and extremely widely used, just
that not all systems have them.

Christian.

On Tue, 14 Sep 2004 12:07:37 +0100, "IMM" wrote:


"Christian McArdle" wrote in message
.net...
"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.

I know few. if any, systems that do not require an auto air vent above the
boiler on the flow pipe. In days gone by when there was no system boilers
with integral pressure vessels and all components had to be external, an
auto air-vent on the flow over the boiler was mandatory by all
manufacturers. You didn't think, you just put one in.


Where components are not present in the boiler, it is common to use a
sealed system kit, consisting of a manifold and the four items listed.
These don't have a vent.

For a vent to be useful near to a boiler implies that there is a
convenient place to install one and that the pipework reaches a high
point immediately above it.

If the pipework is at the bottom of the boiler, then it should have an
integral vent to be able to vent the heat exchanger.

Other than that, vents should obviously be at high points on the
system.



..andy

To email, substitute .nospam with .gl

On Tue, 14 Sep 2004 11:31:53 +0100, Christian McArdle wrote:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.


Although combis are invariably sealed systems and invariably contain an
automatic air vent I did not consider that they were an _essential_ part
of a sealed system.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

On Tue, 14 Sep 2004 19:40:14 +0100, Andy Hall wrote:

On Tue, 14 Sep 2004 12:07:37 +0100, "IMM" wrote:


"Christian McArdle" wrote in message
x.net...
"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.

I know few. if any, systems that do not require an auto air vent above the
boiler on the flow pipe. In days gone by when there was no system boilers
with integral pressure vessels and all components had to be external, an
auto air-vent on the flow over the boiler was mandatory by all
manufacturers. You didn't think, you just put one in.


Where components are not present in the boiler, it is common to use a
sealed system kit, consisting of a manifold and the four items listed.
These don't have a vent.

For a vent to be useful near to a boiler implies that there is a
convenient place to install one and that the pipework reaches a high
point immediately above it.

If the pipework is at the bottom of the boiler, then it should have an
integral vent to be able to vent the heat exchanger.

Other than that, vents should obviously be at high points on the
system.

Indeed so, and they do not need to be automatic.
In my own home the highest points are the 4 upstairs radiators, the top of
the indirect cylinder coil and the top of the boiler's heat exchanger.
Only the latter has an auto vent. The others are manual.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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

"Ed Sirett" wrote in message
n.co.uk...
On Tue, 14 Sep 2004 11:31:53 +0100, Christian McArdle wrote:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed
pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.


Although combis are invariably sealed systems and invariably contain an
automatic air vent I did not consider that they were an _essential_ part
of a sealed system.

I would.

On Thu, 16 Sep 2004 01:04:50 +0100, IMM wrote:


"Ed Sirett" wrote in message
n.co.uk...
On Tue, 14 Sep 2004 11:31:53 +0100, Christian McArdle wrote:

"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed
pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.


Although combis are invariably sealed systems and invariably contain an
automatic air vent I did not consider that they were an _essential_ part
of a sealed system.

I would.

There is nothing to stop you writing your own superior FAQ with Answers on
Sealed CH systems.

From my point of view a FAQ document is neither intended nor required to
give information on every aspect of the subject. Indeed there is no mention
in my FAQ on selecting the size of the vessel or precise adjustments for
very tall systems (e.g. 5 storey town house.).

The FAQ has already made a dent in the number of postings on the subject,
and freed up time effort for other more unusual questions to be discussed.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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