DIY Doctor

Fuse Box wiring

Postby fordangliagnome » Sat Dec 31, 2011 2:31 pm

I have an old style rewirable MEM cream metal fuse box in my house.

The wiring in the house is all twin cable black/red with earth in between and I suspect that the house was rewired during the 1980s

On the fuse box there are TWO 30a fuses marked for sockets, but I notice that if I pull ONE of the two fuses out the sockets circuit is still live. Looking past the fuse there are two twin and earth wires feeding from each fuse.

My query: is this normal wiring practice or has one of the two pairs of twin & earth been wrongly connected for the past 30 years? eg should there be a separate ring main from each of the two fuses ?

I am about to get a quote for changing the fuse box for a more up to date and safer one, what should I be asking for?

Any advice appreciated to stop me from being ripped off.
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Simply Build It

Postby BLAKEY1963 » Sat Dec 31, 2011 10:23 pm

When the fuse board is changed your part p registered electrician should issue you with
an electrical installation certificate , which would descibe the condition of your existing
wiring . This would answer your question regarding the ring mains.
You could ask him for a price for the work and whats included before he starts.
A FEW prices from registered electricians are normaly the thing before engageing anybody
to start work
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Postby ericmark » Mon Jan 02, 2012 1:50 am

It does sound if wired wrong. However since your going to get it sorted does it really matter?
However my father's house has been added to and added to over the years. Originally it had 5 sockets on the ring. When I came to sort out the electrics after the electrician had run off without finishing I found I had to disconnect a number of sockets where overload over many years had degraded the insulation.

With a board change what you want is a trouble free transition. So you need an electrical condition report to identify problems before the work starts. Once all circuits are on RCD any problems will be highlighted.

It is easy to make mistakes and I have seen where radials have been joined by some one who has not realised they were radials and thought they were correcting an error. Also where people thought radials were rings and have not realised it was all wired in 4mm not 2.5mm.

To remove every single socket and inspect the cables is very time consuming, the normal is to remove a number and if no faults are found assume nothing wrong with rest, and only continue removing sockets when faults are found. The problem is removing sockets can produce faults so not always good to remove all sockets which also can mean plaster cracks around them as they are removed.

So one tends to single out those which look as though they may be faulty in some way.

My daughters house seems very odd to me. And my son thinks the same. We have guessed at some time in the past when the garage was made into a room that the consumer unit has been moved. However we can't find where it was or where cables have been joined. Everything tests OK but we are not happy.

But one is not inclined to knock a hole in a wall to see if there are wires behind it unless there is a problem.

So any help you can give the electrician will in turn help him decide what extent to go in testing and inspection. A floor plan showing all sockets is often helpful. I have DVD's with pictures taken in my dad's house and daughters house under the floor boards labelled as to where taken. Normally where board was removed to do something or where ceiling has been re-done. All helps next time to remove the right bit of carpet or floor board.
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