ABSTRACT
Fixed appliances of small ratings, by which we mean up to 3 kW, can be served through fused connection units from the ring mains serving the socket outlets in the same area as the fixed appliance. A 3 kW electric fire is one example of a fixed appliance which might be supplied in this way. If the socket outlets in the area are on radial rather than ring circuits then each fixed appliance must have a separate radial circuit of its own. It is often convenient to supply equipment such as motorized valves on hot water heating systems, roof mounted extractor fans in kitchens, tubular heaters in tank rooms and so on by a separate circuit for each item or group of items. There is nothing wrong technically with supplying them by a fused connection unit from an adjacent general purpose ring main provided the permanent load they put on the ring is taken into account in assessing the number of socket outlets that can be permitted, but these items have a different function from the general purpose socket outlets and it is logical to serve them separately. Separation by function can be an asset to maintenance; there should be no need to lay dead all the socket outlets in part of a building when work has to be done to a toilet extractor fan. On the other hand, a separate circuit to one small piece of equipment may seem an extravagance. No general rule can be made, and the designer must decide each application on its particular circumstances.
