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Cable size

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uksparks

uksparks

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Hi,

I am going to be connecting an out door power supply, away from the building, its all metal casing.

The supply is 10mm, I am using a 3 core SWA for part of the run, the inside part was going to be in twin and earth, but then I was just thinking, going on table 54.8 section 544.1, am I looking into this too much or does it need to have a 10mm earth as its extraneous metal which is fixed into the ground?

In which case I was just thinking of running 3x 10mm inside the building so the earth is 10mm too to them comply with min size of bonding conductor.

I am right to make it 10mm throughout the entire run aren't i?
 
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uksparks said:
ah i see!
Click to expand...
ecb7171239ea7cb07bb84a69a4c6c3b2.jpg


im usually organized
 
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uksparks said:
I have got to dig a 2ft deep hole anyway for the mounting plate to be sat in, so can just dig across a little bit and see whats there, unlikely theres anything where this is going though.

What do you think? 2 rods maybe? Its next to a marina too, so the ground might be quite wet (if it leaks)
Click to expand...

Famous last words mate. Don't risk it. Especially if 2 rods are required. We install 1 rod at a time then test. No point going further than required.
 
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Just a thought if he does TT it, it is close to a metal clad building which is itself TNCS/PME and also likely to be bonded via the structural steelwork , your are not supposed to be able to touch two different earthing systems simultaneously, this can itself be a shock hazard due to the differences between true earth (TT) and the PME earth.

I don't know the reg number off the top of my head, and it may be a DNO rule, I would have to look it up to back this statement up.
 
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UKESRail said:
Yep. If you are planning to work for this customer again I would recommend installing to the 3rd. You don't want some idiot slagging you off in 7 months time saying "he gave you an out of date installation mate". Even though he would be wrong.
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He's got more worries than just that if he's installing less than 20mtrs of new SWA with a plastic joint box in the middle of it, not bonding a lump of metal that the charging point is fixed to and connecting it all to a PME supply.
 
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spark 68 said:
Just a thought if he does TT it, it is close to a metal clad building which is itself TNCS/PME and also likely to be bonded via the structural steelwork , your are not supposed to be able to touch two different earthing systems simultaneously, this can itself be a shock hazard due to the differences between true earth (TT) and the PME earth.

I don't know the reg number off the top of my head, and it may be a DNO rule, I would have to look it up to back this statement up.
Click to expand...

This was my other part of the jigsaw, its too close, and I know its bonded as have seen it all inside against the back of the skins.

Hmm its not very straight forward is it.

I say just connect to the PME system, its too close.
 
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spark 68 said:
Just a thought if he does TT it, it is close to a metal clad building which is itself TNCS/PME and also likely to be bonded via the structural steelwork , your are not supposed to be able to touch two different earthing systems simultaneously, this can itself be a shock hazard due to the differences between true earth (TT) and the PME earth.

I don't know the reg number off the top of my head, and it may be a DNO rule, I would have to look it up to back this statement up.
Click to expand...

it is a minefield eh?

It it is unusual for DNOs to provide earths to metal framed building is it not?

This is job may need a step back and reasses. Many heads are better than one.
 
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uksparks said:
Im going continuous now actually, you are not up to speed LOL.
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It's hard to keep up to be honest, in the last thread about this you had decided to use a three phase unit and now you're back to single phase again. Now you're wandering off into the realms of whether or not it can be connected to PME or not and if it needs earth rods or not.
I thought you would have had this installation designed by now.

Where are you thinking of connecting the earth rods and why? What value of Ra do you need to achieve?

I'd personally be looking to comply with the requirements of (ii) in the list of situations where PME can be used. I can see the sense in divorcing the PME connection and relying on earth rods for one charging point when 99.9% of the time the PME will be fine, and the other .1% of the time the earth rods connected to the MET could benefit the entire installation.
 
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spark 68 said:
Just a thought if he does TT it, it is close to a metal clad building which is itself TNCS/PME and also likely to be bonded via the structural steelwork , your are not supposed to be able to touch two different earthing systems simultaneously, this can itself be a shock hazard due to the differences between true earth (TT) and the PME earth.

I don't know the reg number off the top of my head, and it may be a DNO rule, I would have to look it up to back this statement up.
Click to expand...
Should a metal clad building be PME anyhow? I thought not.
 
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uksparks said:
This was my other part of the jigsaw, its too close, and I know its bonded as have seen it all inside against the back of the skins.

Hmm its not very straight forward is it.

I say just connect to the PME system, its too close.
Click to expand...

Absolutly do do not approach it like this mate. If the neutral breaks down on the DNO side and someone goes to use the VC point then their body may well be the return path back to earth.

All together we can get there I am sure.
 
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I really do appreciate Kate all your help and constructive feedback on this, it's an area that itself has had the regs fiddled with and also other issues like earth rods and distances to the building.

Ok so if we break it down into small chunks, let's hypothetically say we will go with the earth rod, it says connect it be k to the met. Do we have any information anywhere as to what reading is acceptable that we must achieve?
 
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uksparks said:
I really do appreciate Kate all your help and constructive feedback on this, it's an area that itself has had the regs fiddled with and also other issues like earth rods and distances to the building.

Ok so if we break it down into small chunks, let's hypothetically say we will go with the earth rod, it says connect it be k to the met. Do we have any information anywhere as to what reading is acceptable that we must achieve?
Click to expand...


Kate???
 
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