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Quote: Originally posted by The 2 Tops on 05/3/2011

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Quote: Originally posted by saxo1 on 04/3/2011

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Call me picky if you like but a fuse will blow on overload if it is in the neutral,try it if you don't believe me,and a plug in tester wont detect a neutral earth swap because your RCD will trip first!

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Saxo1

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As earth and neutral are the same potential, I can see why a swap wouldn't be detected.  But, as the tester forms  a low current circuit and not a short circuit, I cannot see why the RCD should trip.

The other point, about a fuse blowing in the neutral side of the circuit is correct.  I can remember the old days of comsumer fuse boxes being fused on both live and neutral, and the fuse on the neutral side being the one to blow.

Bertie. 

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There is little doubt that a fuse on the neutral side will blow in a dead short scenario and yes a weaker fuse will blow first.

I recall something about fuses on the neutral side blowing before the live, in the past, as Bertie has pointed out, but believe this may be due to ‘tempering’ of the live fuse.  It is my contention that as the load is on the live feed and as energy is consumed and given off by the appliance that a fuse on the neutral wire is less likely to blow in an overload situation.

Irrespective of all this ‘tecnobabble’  a fuse blowing on the neutral side would leave an appliance live as in a reverse polarity scenario.

Regards all, Bob

The load is equal on both fuses, and either is capable of blowing; and yes, I agree that a weaker fuse will be the one to blow, whether it's on the live or the neutral side.

I once had a large old Edwardian house that had numerous D.P. fuse boxes.  Before I finally rewired the whole house, complete with new distribution booard, I increased the size of the neutral fuses to ensure any blown fuse occurred on the live side of a circuit.  Some of the original fuses resembled a stubby ceramic pepperpot; screw-on top cover with three vent holes, and the fuse immediately behind it.

I often did a few installations for other people (properly passed by the electicity board), and one of the most scary situations I came across was a request for an additional power point to put an electric fire in a bedroom.  When I looked in the meter cupboard, there was only a box for one circuit.  There were already power sockets downstairs, and one in a bedroom.  You could trace cable runs by warmth through the floorboards.  The D.P. fuses had been increased to around 45 amps  with what looked like strands from  7/.044" cable wire.  Needless to say, I advised the householder of a fire risk and quickly departed.

Bertie.