Electrical Question

Fuse box

Hi my toaster tripped the main rcd in the fuse box but not the individual trip fuse for the plug sockets. The toaster is still working so is the plug socket. The individual fuse is a B32 on a wylex fuse box. Why did it not trip the individual fuse?

2 Answers

Best Answer

The B32 BSEN60898 MCB can only operate under short circuits (i.e. Live to earth faults) and overload type faults. Whereas the BSEN61008 RCD can operate on Neutral to earth or Live to earth faults. It is a lot more sensitive than a normal circuit breaker and is used to protect several circuits.

Its possible that the toaster caused the RCD to trip when the toast popped up as the power to the heating circuit inside the toater was shut off. Its a known issue for RCD's to operate if the Live and Neutral are not isolated simultaneously.

The toaster can be PAT tested and if the insulation resistance and earth leakage results are fine, then there is no need to replace it. If it fails the PAT test then it is advisable to buy a new one. A PAT test costs about £3

Answered 19th Nov 2012

Electrical Safety Services

Member since 17 Oct 2011

Hi, the reason the RCD tripped first is because it is much more sensitive than the cicuit breaker. Its job is to monitor the current that is being used between both the live and the neutral of the circuit and if there is an in-balance it will trip and cut the power off. The RCD will probably have been 30 milli-Amps, where as the circuit breaker will be around 30A, therefore, it's would take a fault of over 30 Amps for the breaker to trip but only an in-balance of 30 milli-Amps for the RCD to trip.

Your toaster must have created an earth fault some how, i would get a new one just to be on the safe side,

hope this helps.

Answered 19th Nov 2012

Efficient Electrical

Member since 1 Aug 2012

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