Earth at distibution cable


Postby remelad » Tue Apr 29, 2008 10:35 pm

Hi All,
in an earlier post i asked about an earth that was shared with the neutral within the consumer unit. I have since discovered a wire about 1 inch that is soldered to the main intake cable,as this is not a long enough in length to do anything with i was going to use an earth clamp BS951 and clamp to the lead sheath of said mains.Have looked into this and found that this is not acceptable even though REC do this when they upgrade company service fuse. Is there an alternative clamp for this connection to be acceptable,if not would this idea be okay? Leave the earth clamp on then put a heavy duty crimp on the 1 inch wire,terminate this to the clamp, with a 10mm earth cable with a crimp on also terminate this to the clamp then run onto a MET.
I will do an external earth loop impedance test first to ensure this 1 inch wire is okay for use.
Any comments or suggestions very welcome
Remelad
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Postby ericmark » Wed Apr 30, 2008 12:18 am

The supply authority are responsible for informing you what earth system you should have. Ring them up and ask them. Either they will tell you straight away or send someone out. They don't have to provide an earth but all houses in same area must have same system and if you are to have TN-C-S or TN-S they will provide it for you and test it. And if you have a TT system then you have to use earth rod and RCD's but it is not up to you the supply authority must decide.
ericmark

Postby remelad » Wed Apr 30, 2008 7:56 am

Hi ericmark,
thanks for your quick reply, so are we saying even though its not the responsibility of the supply company to provide an earth, if it's TN-C-S or TN-S they will supply said earth.
I have rang EDF supply and have found them very hard work, i will ring them again
I see you sleep about as much as me looking at the time of your reply.
Many thanks Remelad
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Postby ericmark » Wed Apr 30, 2008 1:14 pm

Yes our supply authority also a pain. If you ask them for an earth they will just tell you they don't have to provide one. Which is true. But if you ask what type of earth you should have then they are duty bound to tell you as it is up to them to select earth type for the area. There are dangers if you have one type of earth and next door has a different type. Also you can ask them what is the earth loop impedance at the supply where a TN-C-S or TN-S supply is given. There are three types of supply to houses in the UK. TT is where there is not earth supplied from the supply authority and the house owner has to supply his own. Normally a overhead supply but sometimes where originally there was an overhead supply to some houses connected to that transformer and in order to keep all on the same system TT is still all that is provided. The owner needs to use earth rods, there are some other things that can be used but not the supply gas or water pipes. To ensure a fault will trip a MCB or blow fuse quite a good earth is required it could require earth mats and multi earth rods to draw enough current to trip a 100 amp incoming fuse so to ensure the supply is removed under fault conditions earth leakages trips (RCD) are used. These are selected according to how good the earth is but normally 100ma type is used. With the other two systems which as far as user is concerned are the same a RCD for fault protection is not required. Although for personal protection you may still require a number of 30ma or less RCD's
Most houses have a TN-C-S supply with an earth supplied by the supply authority this is also called PME another name for same thing.
ericmark

Postby remelad » Thu May 01, 2008 9:19 pm

Cheers for the help young man.Local supply company still playing up, they just pass you round and round.
Regards Remelad
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Postby ericmark » Fri May 02, 2008 4:37 pm

I know the feeling in the past customers have had change billing agent so it is same as supply authority to get things sorted.
ericmark

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