I am needing to replace my old Glow worm 92/100b floor standing boiler with a wall mounted similar size boiler. how do i determine if it is a sealed or unsealed system

Mark Armstrong, January 2007

a unsealed system has a small f/e tank in loft. fed by a ball valve from the mains water. a sealed system has an exspansion vessel (like a red foot ball) instead of a tank and the system is filled by a filling loop of the mains water to a certain pressure. this system is under pressure. unsealed is gravity pressure

hi-spec plumbing, January 2007