Hello John:
Assuming that the system is sealed, which is quite likely
as you are
mentioning that you have a pressure gauge on the system,
when the system is
cold, the pressure will be less than when it is hot as
the
water will expand
as it heats to, say, 60C.
In order to keep the pressure at a constant level (you
mention a typical 1.5
bar) their needs to be scope for expansion to maintain
that pressure.
This is achieved with a pressure vessel which is made of
metal and typically
has a three quarter inch BSP female connector and is
fitted onto either the
flow or return of the system which has a T connector onto
which it fits.
In a typical 3 bedroom house, this would be about 6
inches
in diameter, and
about 8 inches long.
Across its equator is a flexible membrane, and at the
opposite end to its
BSP connection is a Schrader valve.
When the system is cold, a pump is applied to the valve
to
establish the 1.5
bar pressure.
As the system expands, the membrane is displaced thus
increasing the volume
of the system, hence maintaining the chosen pressure.
Boyle's law:
Pressure times volume equals constant.
The size of this vessel is determined in proportion to
the
total of the
volume of the system.
Sorry for the mix of quoted units, to make it more
correct, I should have
mentioned atmospheres in stead of bars, thus making the
description totally
in imperial units!
Hth
David
-----Original Message-----
From: access-uk@xxxxxxxxxxxxx
[mailto:access-uk@xxxxxxxxxxxxx] On Behalf Of
John Wilson
Sent: Wednesday, April 09, 2008 12:54 AM
To: access-uk@xxxxxxxxxxxxx
Subject: [access-uk] For David Wood: was: combi-boilers.
Hello David,
Thanks for the feedback.
However, what is this pressure vessel. I have never heard
of
such a thing. Perhaps my type of combi-boiler does not
employ one. There is no mention of this in the manual I
was
left and no one has mentioned such a thing to me.
John.
----- Original Message -----
From: "David W Wood" <g3yxx@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: <access-uk@xxxxxxxxxxxxx>
Sent: Tuesday, April 08, 2008 7:01 PM
Subject: [access-uk] Re: O/T but does anyone on the list
have an Ideal Isar combi-boiler?
Hi John:
I have had a sealed system in my work premises for some
20
years, purely for
16 radiators on the ground floor with a conventional
vented system with 10
radiators and hot cylinder on the first floor.
I have always had the same problem as you with the
sealed
system, and no
sign of leaks.
One important point is to make sure the pressure vessel
is
kept topped up -
this should be shown to you by the installers.
The reason for the boiler rattling will be because of
build-up of gases
which will accumulate in the high point or points of the
installation.
David
-----Original Message-----
From: access-uk@xxxxxxxxxxxxx
[mailto:access-uk@xxxxxxxxxxxxx] On Behalf Of
John Wilson
Sent: Tuesday, April 08, 2008 4:04 PM
To: Access UK
Subject: [access-uk] O/T but does anyone on the list
have
an Ideal Isar
combi-boiler?
Hello All,
Sorry for the O/T posting but I'm sure that some people
on
here will be able to compare notes and give valuable
feedback.
I have had an Ideal Isar combi-boiler now for a year and
am
of the opinion that the pipework may be leaking under
the
downstairs floor boards. Other people I have spoken to
(but
with different boilers) tell me that they rarely, if
ever,
have to top up the pressure in their central heating
system.
However, I find that I have to do this every three or
four
weeks. The pressure will have fallen from the
recommended
1.5 bars to only 0.5 bars or even lower, causing the
boiler
to become noisy with a vibrating effect.
Does anyone else find this to be the case with these
boilers
and systems? I am about to report it to the fitters but
wanted to know what the norm for the frequency of
pressure
top up of these systems is firstly from any other users.
All contributions appreciated.
John.
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