I am aware that unvented mains pressure systems need to be installed by an approved plumber and need some form of pressure relief valves installed.
I assume ch boilers have a valve included on the heating side but another needs to be installed on the mains fed side.
But how many? When do they get tested? How are they tested? Do they get tested? Should they be renewed? When should they be renewed? Are they adjustable? Should they be adjustable?
Cheers.