[access-uk] Re: For David Wood: was: combi-boilers. longish reply
- From: "David W Wood" <g3yxx@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- To: <access-uk@xxxxxxxxxxxxx>
- Date: Wed, 9 Apr 2008 06:58:32 +0100
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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