The system is equipped with an expansion tank and automatic make up.
I have never heard of a automatic make up but if it has expansion tank then it's a presurized system. The system when upto pressure should be disconnected from the main supply so that if the check valve decides not to work then the heating water wont get pushed back into the mains water line and contaminate the mains drinking water or if someone turns on the refil valve it wont keep filing up the system to what ever mains pressure you have and cause an explosion.
As an example you should have a isolation valve then a removable flexable hose then a check valve(Non return valve) so that when system is charged you can shut of the water supply and cap the valves after you remove the flexi.
But you can shut of the mains water with this type of system. Also most new boiler have a low limit stat so that when the temp drops below a certain tempreture the system will fire up and run no mater if the stat is turned off or not. This is so pipes dont freeze over winter.