Unvented Pressurised Hot Water System

[ETBT]

Could anyone tell me please if the storage tank in the above water system is filled to capacity or partially filled

[buildersmate]

They are most normally filled full with water. The pressure control method (to maintain a pressure in the system of around 1 bar) is typically via an expansion vessel with a bladder across the middle.

[ETBT]

Thank you

[taffdavies1]

Your question is about a pressurised water system.
O.K. i assume you know the difference between a pressurised system and a non pressurised system?
Easy peasy. A non pessurised system has an expansion tank in your loft which is capable of accepting 20% of the expanded water in your heating system when it reaches 100deg Celsius.
A pressrised system on the other hand expands that water either in a sphere close to your cylinder. or on the boiler itself as in a combi.
Inside the sphere is a neoprene bag, right across the middle. As water pressure is exerted one side, its counteracted by air pressure the other side. By elimination your friendly heating engineer can eliminate what problem your heating system has, and fix that problem accordingly. Simples.