DIY Doctor

upgrading central heating from open to closed pressurised

Postby builder brad » Thu Apr 03, 2008 9:34 am


I am looking at upgrading my central heating system from an open circuit with expansion tank to a closed, pressurised system. I am keen on the benefits of a closed system and aware of most of the potential problems.

I live in a single story building and am not worried about the potential to save space with the expansion vessel - and for this reason I am happy to site this in place of the current expansion tank which is some 8 metres away from the boiler - is this OK? most of the info I can find on this subject seems to recomend placing the vessel right next to the boiler.

My system uses oil and a Boulter Camrar Compact boiler, it has always knocked and banged and the radiators have only lasted 8 years, despite having inhibitor added.

builder brad
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Postby Gareth Thomas » Sat Apr 05, 2008 10:45 am

:D Change the oil boiler for a Condensing Combi, good makes are Trianco, Grant etc. These boilers have the expansion tank built in to them, hence no problem with where to put your expansion tank. Modern day regs dictate that it has to be a condensing boiler. Just go along to someone like Plumb Center, and let them know your requirements (How many rads, domestic water demand etc), and they'll tell you what sized boiler you require.
Have to admitt, I've never heard of a Boulter camray or whatever it was boiler??!!
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Postby Perry525 » Sat Apr 05, 2008 12:45 pm

You wrote that you are aware of the potential problems. However, let me run over some of the ones I feel are important.
The most important, is the possible effect on the resale of your house.
A lot of people having tried closed systems have identified that they are not for them!
You will have no emergency store of water!
When a main breaks, or someone diggs it up, you have no water.
You cannot, wash, shower, flush the loo, have a cup of tea, without driving to the nearest open supermarket and buying bottles of water.
If you have a baby or young children, having to find an open supermarket in the middle of the night can be a challenge. Using expensive water to flush the loo can be off putting?
If you live by yourself, or with one other person, and you know what they are doing at all times, perhaps OK.
If you have a family, and are taking a shower and someone turns on a tap and you loose your hot water, and you are left covered in soap and cold - not exactly a pleasure!
Even having to think!
Can I put on the washing machine, or dishwasher? Will it cause a problem over the next hour or so?
If someone wants to wash, shower run a bath - do you want these problems?
Is your mains pressure high enough to run the system?
Will it provide water to two taps?
Will it work at times of high demand?
Keeping in mind that closed systems use far more heat to heat your washing water, and therefore, waste more heat, do you want the additional expense?
With an open vent system, its fit and forget, for most of us.
Would it not be better to wait until your current system needs replacing? Before spending all that money?
You can invest in an ISA and get 6.5% on your money.
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Postby Skids » Sat Apr 05, 2008 7:47 pm

Hi builder brad,

You need to start with the fuel source? You state you have oil!

Have you got gas, can you get gas supplied to the house?

Are you intending changing the boiler? As you can get Condensing & Combi’s in oil and gas. Regs are pushing towards ‘Condensing boilers’ on new installations.

Yes you could install/run a UNVENTED system, however the cost of installing the system would/could outweigh the benefits.

You can NOT JUST change the F&E tank (expansion tank) for a expansion vessel and call it a pressurised system. Get some books from the library and do some more reading up. As the expansion vessel location/size is dictated by the system.

You say it’s a single story building, however do not say whether the current system is a conventional CWSC fed system or a mains fed thermal store type system. Therefore you will need to consider the water pressure, either at the mains or from the CWSC. And most importantly what pressure you want from the taps?

Don’t forget, although linked (as in heated by the boiler), the CH system is on a different circuit from the CH !!!

( Perry525, Not sure how we got from CH on to hot & cold water ? )


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Postby Skids » Mon Apr 07, 2008 9:42 pm

"Don’t forget, although linked (as in heated by the boiler), the CH system is on a different circuit from the [b]CH[/b] !!!"

what a muppet

second CH should be Hot Water


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