Discuss Expansion Vessel size ? in the Plumbing Jobs | The Job-board area at PlumbersForums.net
True that 10M of head produces 1 bar of pressure but that is static head and not influanced by heat. The pressure increase by 4.5% as the heated water expands from 1° to 100°. We normally use 4% in our calculations as the max heating temp of a boiler is aprox 80°. I worked out almost like for like as ShaunCorbs has. So I would be installing a 4ltr. It is only allows a 0.25ltr buffer but given the lower temp it should easily cope. Or a 4.5ltr if there is an unusually amount of head. Just make sure you fit a 3bar PRV aswell.Thankyou very much for all your answers. I agree that it's better to be slightly over the top , but totally over the top is unsightly & unnecessary.
As I understand it pressure grows by 1 bar in every 10M dropped so I can't see any problems there.
Many thanks again...
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