Q & A of the Day - Can I spur off cooker circuit in 2.5mm cable to power hob/extractor?

Question: I've been asked to connect a new oven to an existing 6mm supply on a 32A MCB, protected by an RCD at the consumer unit (CU). The existing 6mm supply is terminated in a switched fused spur (to power the oven) in a dual metal back box. Another switched fused spur is installed in the adjacent gang (connected via 2.5mm cable to the 6mm supply) to power the hob ignition. The current arrangement is not accessible as it is behind the cupboard next to the oven, although the back is removable.

First question - Can you advise whether it is acceptable to take a spur off the cooker circuit in 2.5mm cables to power the hob/extractor?

Second question - I'd like to extend the 6mm cable into the cupboard to install a double-pole isolating switch for the oven connection. Is it acceptable to extend the 6mm cable via a terminal block in the existing back box and take the 2.5mm fused spur feed from this also?

I have discussed putting an isolator above the worktop, but the customer wants to avoid this because of the walls being solid and tiled.

Answer:

To the first question - As over-current protection will not be achieved by the assumed compliance with Regulation 435.1, you would have to ensure that overcurrent protection for the 2.5mm cables has been achieved by the application of 433.3.1 (ii) and 434.5.2.

To the second question - The 6mm cables can be joined within the back box, which must remain accessible for inspection. As for the jointing of the 2.5mm cable, see answer 1 above.

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