Abstract: An electrical control unit has specific application to central heating systems in which a plurality of electrical connections are to be made to the unit. The unit includes a backplate to which electrical connections may be made at a plurality of positions. A housing, containing control circuits and contacts for making connection between the circuit and the backplate connections, is removably attached to the backplate. Access to the electrical connections on the backplate for testing purposes may be achieved with the housing attached and electrically connected to the backplate, but a cover on the backplate may be positioned to prevent such access during normal operation of the unit. The unit also includes two control switches of which one is operable independently of the other or of which both are independently operable upon release of an interlock. The control circuits include a printed circuit board on which one side is printed.

Abstract: A cast metal heat exchanger (e.g. of iron or aluminum) for a hot water boiler having a plurality of flueways and waterways and which is rectangular in plan view down onto the flueways with the waterways extending parallel to the minor rectangular axis. A method of manufacturing a cast metal waterway section of cuboid volume less than 4500 mls for a heat exchanger (which comprises casting the metal into a mould with the waterway core vertically disposed. A heat exchanger comprising a plurality of such sections can be formed integrally by vertically casting such a plurality simultaneously in one mould.

Abstract: A control apparatus for a fanned, gaseous fuel-burning appliance, such as a water boiler for a domestic central heating system; the control apparatus includes electrical circuitry comprising first and second changeover switches each having a normally-closed pair of contacts and a third, normally-open contact, and a third switch; the switches are connected in a particular way to actuate gas valves and the fan of the appliance in a manner which provides improved safety features.