Converting central heating to sealed system

15 Dec 2009
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Whitby N Yorks
United Kingdom

Soon after I installed my new oil central heating system (open vented) using a Danesmoor 15/19 boiler I was advised I should have installed it as a sealed system.

I hope to get round to converting to a sealed system shortly but am hoping someone can give me some advice.

As far as I am aware it is a fairly simple job. In principle all I need to do is remove the header tank in the loft & replace it with an expansion vessel. At the same time I need to fit a pressure release valve.

I assume it is not important whereabouts in the system these new components are fitted?

I note Screwfix supply a range of expansion vessels 8 12 18 and 25 litre. How do I decide which size is most appropriate?

Thank you

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The main thing, and I haven't a clue about any oil boiler, is the the boiler has a built in overheat stat. Has your's got one?

This is a requirement for a sealed system.
If its working ok then don't bother converting it to sealed. If it ain't broke and all that.
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Everything is working fine and has done for the last 12 years. However I seem to remember that the water in the header tank in the loft gets hot when the central heating is switched on. Just seems a pity to waste heat in the loft.

Since I posted I have read other posts asking for the same advice and I have realised fitting a sealed system is not as straightforward as I first imagined. In particular I did not realise the sealed system was not left connected to the mains and would have to be checked periodically to see if it needs topping up. I thought it would be OK to leave it connected via a pressure reducing valve and non return valve so topping the system up would be automatic.


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