Published:
14 April 2014
Category:
Q&A
Jon asks this question, which is about installing a new kitchen hob, its cable and the circuit protection. It has been answered by the NICEIC (Theme – Distribution Equipment including Cable Management):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: I’m replacing a kitchen hob. The original hob was a solid plate type, while the new one is an induction type and is fitted with a three-core 1.5mm PVC cable about 1meter long. The hob circuit is a 10mm twin & earth cable on 32A MCB. From the cooker outlet, a fused spur is connected that supplies the oven.
Is it OK to connect the cable on new hob to the cooker outlet?
I understand that the cable won’t become overloaded, but my concern is fault current. If I use the adiabatic equation to calculate the minimum circuit protective conductor (CPC), and it is under 1.5mm, can the 1.5mm cable be connected to the 32A cooker outlet and use MCB for short circuit protection only?
This is how I’m reading the regulations. Note that I can’t de-rate the 32 cooker outlet to a 20A version, as this could trip if the oven was also on.
Answer: You need to consider the following key regulations:
- 433.3.1 (ii), which permits overload protection to be omitted where the characteristics of the load are not likely to carry an overload current. However, protection against fault current must be provided as required by Section 434.
- 434.2.2 would permit fault protection by the 32A circuit breaker, provided that it satisfies the conditions in Regulation 434.5.2 (the adiabatic equation).
In summary, your proposed circuit arrangement would comply - subject to meeting the above conditions.
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