Chris is spot on with his description of a potable water expansion vessel. At max expansion, the balloon wont fill the vessel, but it will be close, although you generally oversize the expansion vessel (so you'll never get max expansion) to prevent the pressure from exceeding the safety valve setting on an unvented system - too much expansion volume is always a good thing.
As for patents - whats to stop someone fitting such a vessel 'to combat water hammer'? Seems to me OSO are just good at marketing (I am biased btw so take any anti-OSO comments with a pinch of salt )
When does a shock arrestor become an accumulator? 0.5Litre like on a thermal store? 12 Litre like on a 150 Litre unvented cylinder? 100 Litre on the incoming mains?
CCM
As for patents - whats to stop someone fitting such a vessel 'to combat water hammer'? Seems to me OSO are just good at marketing (I am biased btw so take any anti-OSO comments with a pinch of salt )
When does a shock arrestor become an accumulator? 0.5Litre like on a thermal store? 12 Litre like on a 150 Litre unvented cylinder? 100 Litre on the incoming mains?
CCM