Hello, I'm new to the site so please be kind. Currently the set up in my flat is as follows. Consumer unit with 40amp mcb connected to 6mm cable to a cooker socket. A 2.5mm cable is fitted directly into the cooker socket and goes to an electric oven rated at 2.4kw max. Is this acceptable? Advice would be greatly appreciated.
The idea of a protective device (M.C.B or fuse) is to protect the cable. So the cable must be higher rated than the protective device so that in the event of a fault it can safely carry the current until the protective device operates.
As you have a 40A mcb protecting a 6mm cable that is acceptable but should a fault occur in the oven then the lowest rated thing will fail first, which in your case is the 2.5mm cable, so the answer to your question is, no not only is it not acceptable, it is dangerous.
People will often say "You must be wrong because it works" Yes it does work, but its when it goes wrong that the error will be seen, by which time it is all too often too late.
Fit a FCU (fused connection unit) at the cooker is the easy way if cooker less than 3 kW, if over 3 kW then change the MCB. The latter best done by an electrician as there may be live parts exposed when you go into a consumer unit.
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