The location may differ but the airing cupboard is usually above the heat exchanger. When the communal block heating system is working the airing cupboard is excellent. For the summer, there is a small electric heater in the cupboard, with a switch at the back, to provide alternative warmth in the airing cupboard. The metal grill cover is there to stop it over-heating so please don’t remove this or smother the heater completely as this could cause a fire. The second switch, marked “heater”, controls the booster fan for the heat exchanger.