A cooker switch complying with BS 3676 or a cooker control unit complying with BS 4177 (a cooker switch incorporating a socket-outlet) is usually installed where a cooking appliance is to be connected other than by means of a plug and socket-outlet.
For reasons explained at the end of this article, it is usually better to provide a cooker switch rather than a cooker control unit.
A cooker switch or cooker control unit may serve the following functions, where applicable, in respect of a cooking appliance:
- A means of isolation (Section 461 and Regulation Groups 476-02 and 537-03), to facilitate, for example, electrical repair of the appliance without having to isolate at the consumer unit
- A means of switching off for mechanical maintenance (Section 462 and Regulation Group 537-03), to avoid the risk of burns, such as from a heating ring, or mechanical injury, such as from an oven fan, as a result of a switch on the appliance being accidentally turned on during cleaning or mechanical repair of the appliance
- A means of interrupting the supply on load. Such a means is required by Regulation 476-03-04 for every fixed or stationary appliance that may give rise to a hazard in normal use. Alternatively, a suitable means incorporated in the appliance may be used to fulfil this function.
At a nominal voltage of 230 V, a current rating of 30 or 32A is generally suitable for the cooker switch/control unit (and the associated dedicated final circuit) supplying most household cookers, which consist typically of four heating rings, a grill and an oven. However, a higher current rating may be necessary where supplying a cooker having additional cooking facilities and/or a large capacity oven.
An assessment of the likely maximum demand of a household cooker can be made by taking the first 10 A of the rated current plus 30 % of the remainder of the rated current plus 5 A for the socket-outlet of a cooker control unit, if one is fitted.
A cooker switch/control unit may be used to control two or more cooking appliances in the same room (such as an oven/grill and a separate hob unit), as permitted by Regulation 476-03-04, provided it has sufficient current rating.
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