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Industrial Unit Earthing Arrangement - Lack of

Discuss Industrial Unit Earthing Arrangement - Lack of in the Commercial Electrical Advice area at ElectriciansForums.net

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sleepyfolk

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We’re in the process of replacing the 3 phase installation in our premises, the electrician that came said we should contact Western Power and request a PME, Western Power have said they can’t, we have also asked if they can supply a main earth terminal for us to connect to - they say they can’t.
Currently the only earthing arrangement we have is as follows:
Main bonding from cold water pipe goes to terminal in 3 phase isolator, 3 phase and single phase board has 10mm earth to isolator.
There is no earth from the isolator to anywhere, guess it just uses the SWA of the main incoming 3 phase cable that comes into the isolator.
Electrician says there should be a MET near our incoming supply with a 25mm earth cable from there to the isolator and I presume onwards to the new 3 phase board.
He did say something about using an earth rod if it was a house but thought it a bit impractical due to the size needed for our supply given we are on a concrete and tarmac industrial estate.
Can I have some advice please before I speak to him again.
 
sleepyfolk said:
We’re in the process of replacing the 3 phase installation in our premises, the electrician that came said we should contact Western Power and request a PME, Western Power have said they can’t, we have also asked if they can supply a main earth terminal for us to connect to - they say they can’t.
Currently the only earthing arrangement we have is as follows:
Main bonding from cold water pipe goes to terminal in 3 phase isolator, 3 phase and single phase board has 10mm earth to isolator.
There is no earth from the isolator to anywhere, guess it just uses the SWA of the main incoming 3 phase cable that comes into the isolator.
Electrician says there should be a MET near our incoming supply with a 25mm earth cable from there to the isolator and I presume onwards to the new 3 phase board.
He did say something about using an earth rod if it was a house but thought it a bit impractical due to the size needed for our supply given we are on a concrete and tarmac industrial estate.
Can I have some advice please before I speak to him again.
Click to expand...
Yes, get a different Electrician
 
Where's that 'main incoming cable' coming from?
Being swa….is it an authority cable or a sub main?
 
Pictures here hopefully, here’s the cut out and isolator in the distribution room which happens to be on the opposite side of the wall to our unit, and the internal view of our isolator switch in the unit.

[ElectriciansForums.net] Industrial Unit Earthing Arrangement - Lack of

[ElectriciansForums.net] Industrial Unit Earthing Arrangement - Lack of

[ElectriciansForums.net] Industrial Unit Earthing Arrangement - Lack of
 
The isolator switch that is open is in our unit, the 3P & N supply cable in the top is from the DNO isolator next door in the meter room, the grey bit on top of the switch is not trunking - it’s the cover for the rewireable fuses on the single phase board, the 3 phase board has been removed from our unit hence no cables on the outgoing RYB phases, the single phase tap off the yellow is to a single phase rewireable fuse consumer unit, the earth cable you can see in the bottom comes from said single phase consumer unit, which incidentally is where the main bond to the cold water pipe is, the hot water currently has none nor does the steel mezzanine floor.
Managed to get hold of our chap but he can’t get out until Monday so I’m interested in any advice before then, I know it’s difficult, here’s a shot of what’s in the unit - the 3 phase panel has now gone as it was snagging the stairs

[ElectriciansForums.net] Industrial Unit Earthing Arrangement - Lack of

[ElectriciansForums.net] Industrial Unit Earthing Arrangement - Lack of
 
Last edited:
Best advice is to get an EICR done.

Best get a different electrician as I am not confident the one you are talking to knows what he is on about.
 
It’s part granite and part breeze block, Western Power planning department said the network didn’t support it and it wasn’t their job to provide a MET, see what the man says on Monday I suppose and I’ll report back
 
Well took a little longer to get here but seems we’re running a 35mm earth cable through the wall and expanding an earth block that was hidden away in the distribution room, seems weird even back in the 80s that they just put a 6mm earth cable from the consumer unit to the isolator but guess it must have been ok back in the day!
 
Back in the 80's having an earth in any size was a bonus given what I see from time to time. Spin is right though in terms of Western Power, they will not generally add a PME to a steel from. Normally they advise a TT.
 
sleepyfolk said:
Well took a little longer to get here but seems we’re running a 35mm earth cable through the wall and expanding an earth block that was hidden away in the distribution room, seems weird even back in the 80s that they just put a 6mm earth cable from the consumer unit to the isolator but guess it must have been ok back in the day!
Click to expand...

Have you calculated the size of earth required?
 
I haven’t, the man in the know has, I thought he said 25mm before but he’s told me to get enough 35mm in to go through the wall into the meter cupboard where he’s connecting it in somewhere
 
sleepyfolk said:
I haven’t, the man in the know has, I thought he said 25mm before but he’s told me to get enough 35mm in to go through the wall into the meter cupboard where he’s connecting it in somewhere
Click to expand...

What size is the incoming supply? You’ve shown a 100A cutout, but based on that you wouldn’t need anything bigger than a 16mm earth and actual calculation would probably prove the 6mm to be ok.
 

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