Hello again David,I understand the need for this expansion ability you mention. Yes, the pressure does go up when the system is working/hot. The pressures I have been mentioning have been when the system is working.
As far as this 6 by 8 inch pressure vessel is concerned I have nothing of this kind on the outside of the boiler, so I must assume that it is internal to the boiler unit.
Thanks, all the same. John.----- Original Message ----- From: "David WE Wood" <g3yxx@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: <access-uk@xxxxxxxxxxxxx> Sent: Wednesday, April 09, 2008 6:58 AMSubject: [access-uk] Re: For David Wood: was: combi-boilers. longish reply
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 expandas 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, andabout 8 inches long.Across its equator is a flexible membrane, and at the opposite end to itsBSP connection is a Schrader valve.When the system is cold, a pump is applied to the valve to establish the 1.5bar pressure.As the system expands, the membrane is displaced thus increasing the volumeof 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 thevolume 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 totallyin imperial units! Hth David -----Original Message-----From: access-uk@xxxxxxxxxxxxx [mailto:access-uk@xxxxxxxxxxxxx] On Behalf OfJohn 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 ofsuch a thing. Perhaps my type of combi-boiler does notemploy one. There is no mention of this in the manual I wasleft 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 20years, 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 iskept 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 onhere 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 (butwith 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 fourweeks. 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 butwanted to know what the norm for the frequency of pressuretop up of these systems is firstly from any other users. All contributions appreciated. John. ** To leave the list, click on the immediately-following link:- ** [mailto:access-uk-request@xxxxxxxxxxxxx?subject=unsubscribe] ** If this link doesn't work then send a message to: ** access-uk-request@xxxxxxxxxxxxx ** and in the Subject line type ** unsubscribe** For other list commands such as vacation mode, click onthe ** immediately-following link:- ** [mailto:access-uk-request@xxxxxxxxxxxxx?subject=faq] ** or send a message, to ** access-uk-request@xxxxxxxxxxxxx with the Subject:- faq No virus found in this incoming message. 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