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26-05-2020, 09:02 PM
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Re: Question For Judd

Judd
things have change a lot since I was an apprentice electrician, (1960/5) never took up the trade in the end because i couldn't stand the cold in winter outside
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26-05-2020, 09:27 PM
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Re: Question For Judd

Had a look, the spur is on a dedicated 16 amp MCB, the big issue was the fitting of a 1KW electric heater, that will be used infrequently, you answered the question in consumption as 3kw on this 16 amp spur, I am sure the remaining 2kw will be well within tolerance for computer, TV etc etc. As far as the earth loss is concerned, @ 20 metres, there is a rod set to earth by the Garage Door, maybe to service some antiquated and decommissioned unit on the garage wall, I could strap and additional earth connection here.

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26-05-2020, 09:42 PM
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Re: Question For Judd

Does your incoming service cable include an earth? Most now do but in the old days you had to make do with a spike (earth-rod). Don't use that old rod as an earth. If your service cable includes an earth, the difference in earth values between the supply earth and the old rod could cause problems with parallel earth paths under fault conditions. Best not to use that rod at all if you have a service cable earth, if you have, just disconnect any earth-wires going to it and run some insulation tape round any exposed part of the rod. Make Sure of your earthing arrangements before you do this. If your supply is what they call a PME, there will be a label on the incoming fuse telling you.

Is that old Wylex fuse-board in the photo still in use?
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26-05-2020, 09:57 PM
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Re: Question For Judd

No, that unit was cropped a long while ago, when the electrician fitted the new consumer unit, I made available access to the houses cabling and extended the spike that provided the original earth connection, if I remember right I asked the geezer if another earth could be employed and he said that the earth for the consumer unit could only come from one source, and what I provided was sufficient, that is why, remotely, I would not introduce another earth point without asking.
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26-05-2020, 10:06 PM
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Re: Question For Judd

I sort of understand now what the geezer was saying, if there is more than one earth source, there could be a conflict in the event of a short circuit.
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26-05-2020, 10:13 PM
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Re: Question For Judd

Originally Posted by spitfire ->
I sort of understand now what the geezer was saying, if there is more than one earth source, there could be a conflict in the event of a short circuit.
That's it. Fault current should only travel to one earth source so the maximum amount can flow and trip the MCB in the required time. If a fault current went to another earth source, it would be shared between the two earths and thus extend or negate the trip time.

You could if you wanted, run a 10 mm earth-wire from the spike back to the incoming supply earth so that it is earthed TO the consumer unit earth and not be used as an earth path. This is the same as earthing water and gas-pipes to the main earth and not be using those pipes as an earth.
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27-05-2020, 07:13 AM
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Re: Question For Judd

Its coming back to me now Judd, when I extended the front of the house, there was a spike, which was wrapped and cemented in with the footings. When the new Consumer unit was fitted, I was told a better earth was required so, not wanting to cause upheaval inside the house, I put a strap on the water supply pipe, and ran the earth cable through conduit under the block paviors, around the outside of the house I left the installation open so the electrician could satisfy himself that it had been done in accordance with regulation, and saved me a few quid in labour, same went for giving him access to the cables, the ceiling was completely open, and the cables ran up the wall from below where the central heating boiler is now, he just unshipped them from the old unit, rerouted them through the open ceiling, and down the wall to the present unit. The supply tails were extended to reach the new position of the unit, and run upwards to each side of the unit.







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27-05-2020, 01:12 PM
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Re: Question For Judd

Did you find out what type of incoming supply you have?
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27-05-2020, 02:30 PM
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Re: Question For Judd

The house was built in 64, and the fact that there was a spike with a rigid ish exposed wire going to if I remember right to somewhere by the isolation fuse (That has the seal on it) would suggest there is no onboard earth in the supply.
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27-05-2020, 02:37 PM
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Re: Question For Judd



Haven't looked closely at that, apart from taking meter readings since the Consumer Unit was fitted, the earth pointing bottom right is strapped to the Gas Meter just out of shot, so, there are two earths.
 
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