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Question about earthing at Main Board


TC101

Question

This is a question further to my other thread "Help to check quote".

The house I may be going to rewire is ex-council.

The main board is at the bottom of the stair in the hall.

It is a metal cabinet about 250mm wide x 600mm high and 150mm deep built into the wall with a metal door and contains the meter, the Cut out fuse, Neutral block and a metal consumer unit fixed to the inside of the cabinet.

There is no earth terminal.

As far as I can see (without stripping anything down) the mains comes in in conduit and earthing is achieved by the conduit being connected by to the metal cabinet by a lock nut and gland and the consumer unit screwed to the

metal cabinet.

I thought the best way to earth it was to use an earth clamp onto the conduit just below the gland and connect to an earth block inside the unit.

Would there be any problems with this?

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as said a pic would be could, where does the conduit lead to? I have seen installations using bits on conduit as a incoming earth but these were in flats, and it was a right lash up.

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The earthing arrangements for this would I presume to be the supply companies responsibility.

The cut out will have a method of earthing be it TNC-S or TNS.

You will need to find out what is what.

If there is no visible signs of earthing it will most likeley be a very old cut out in need of changing.

Like others have said a picture speaks a thousand words and better advise can be given if we know what we are looking at.

The type of box you describe sounds like the old wylex in built consumer units, and as a whole where used when all the wiring was conducted in conduit, the box being earthed and each conduit being earthed via the locknut to the box.

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Last time I something similar (by the sounds of it), I applied for a PME. If it's a really old cut-out they generally renew everything and provide a PME terminal.

The cut out on the supply to the house I worked on was OK, the electricity board (well a really p*ssed of contractor!), just added a PME to and made a TNC-S.

I wouldn't recommend using metal conduit as CPC...

Cheers

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Thanks for the comments. I only had a quick look because I was there to price for the rewire and I had limited Access to the main board. However - It is an ex council house in East Kilbride (outside Glasgow). It is a mid-terrace house and a big housing scheme- Council houses dont do TT installations. I assume the supply is just a loop from the house next door Run in conduit in what looks like 10mm VIR cable. It must be standard in that type of house.

I cannot imagine that the Electricity Board have replaced any of the supplies in the street. However I will make the client aware that there maybe a question mark about the earthing before I start the work. I will get a photo of the main board on Saturday when I go over. The funny thing is that the cut on the live and the neutral block look quite new. Maybe I saw it wrong because it is difficult see properly with dismantling a bit and as I was just looking to estimate I was not going to that. I will come back on this. Terry !!

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Thanks for the comments. I only had a quick look because I was there to price for the rewire and I had limited Access to the main board. However - It is an ex council house in East Kilbride (outside Glasgow). It is a mid-terrace house and a big housing scheme- Council houses dont do TT installations. I assume the supply is just a loop from the house next door Run in conduit in what looks like 10mm VIR cable. It must be standard in that type of house.

I cannot imagine that the Electricity Board have replaced any of the supplies in the street. However I will make the client aware that there maybe a question mark about the earthing before I start the work. I will get a photo of the main board on Saturday when I go over. The funny thing is that the cut on the live and the neutral block look quite new. Maybe I saw it wrong because it is difficult see properly with dismantling a bit and as I was just looking to estimate I was not going to that. I will come back on this. Terry !!

Some things you have mentioned here now become a little clearer.

It is common to find "LOOP" that is in one property and out to the next, normally back to back, it was a way of saving cable.:P

A result of this is that the main earth entered the principle building and was carried to the end of loop via earth cable, sheath, or indeed conduit.

Some times the stranded un sheathed earth bond was sent directly through the wall without a care in the world for later use.

I have seen these cables cut out effectively leaving next door without any earthing arrangements.

A little tip from me to anyone doing any kind of electrical work

TEST FOR AN EFFECTIVE MEANS OF EARTHING

It saves all the hassle later.

I always perform this test whenever I do any quote or estimate, it is amazing how many properties where I have had to get an emergency team in to supply an earth.

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Thanks for the comments. I only had a quick look because I was there to price for the rewire and I had limited Access to the main board. However - It is an ex council house in East Kilbride (outside Glasgow). It is a mid-terrace house and a big housing scheme- Council houses dont do TT installations. I assume the supply is just a loop from the house next door Run in conduit in what looks like 10mm VIR cable. It must be standard in that type of house.

I cannot imagine that the Electricity Board have replaced any of the supplies in the street. However I will make the client aware that there maybe a question mark about the earthing before I start the work. I will get a photo of the main board on Saturday when I go over. The funny thing is that the cut on the live and the neutral block look quite new. Maybe I saw it wrong because it is difficult see properly with dismantling a bit and as I was just looking to estimate I was not going to that. I will come back on this. Terry !!

Thanks Terry.

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I would of thought that sounds like it needs a nice new earth rod inserted and made into a TT earth arrangment... by the sounds of it.:|

Clamp onto conduit dont sound good!!!:(

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Hmm a picture would be helpful.

But I think Id go with specs sounds like TT.

Give dno a call they (if you are lucky) will tell you what the supply earthing arrangement is.

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