Shipping container PME

[ferg]

Upcoming job to install lighting and sockets in a shipping container.

Supply is PME to a metal clad steel framed building and the container is sited approximately 2m away from the building. Also a heat pump within touching distance of the container.

Container sitting directly on the ground.

My little brain is going round in circles and was hoping for some guidance from others with bigger brains than mine.

I had a copy of GN8 somewhere but it appears to have vanished, new copy now ordered.

From memory 2 earthing systems should be further than 2m apart and the container should not be connected to the PME earthing.

What is best practice in this situation?

Also if possible the reasonings behind it, I like to at least attempt to understand why I am doing something.

As always help and guidance much appreciated.

 

[buzzlightyear]

TT, did we not have nearly the same post the other day.

 

[ferg]

TT, did we not have nearly the same post the other day.

Probably Buzz but it didn't help my thought process any.

 

[buzzlightyear]

Probably Buzz but it didn't help my thought process any.

I know not all brains are alike, unless you are hooked up to a machine.

 

[buzzlightyear]

From memory 2 earthing systems should be further than 2m apart and the container should not be connected to the PME earthing.

That's correct this post that you have put here come out of it bottom page on this some body asking the question. Or simpler threads.

 

[suffolkspark]

I had a similar install a few years ago, A container housing a biomass boiler... I initially went with TT, but later returned to find they had bolted the biomass chimney to the metal cladding of the main building (which was about 2m away) Thus dropping my Zs at the db in the container to 0.4. So the chimney in real terms then became the earth path so I went back and swapped the Compression gland on my supply for an armoured gland. I left my stake in anyway. Which in the event of loss of PEN would still have a lower ra than a person. So I'd say if you've got any services running between the two that's something to think about.

 

[Pretty Mouth]

Cut and paste from engineering recommendation G12, it doesn't answer your question, but might help:

6.2.12
Metal clad buildings
Where metal clad buildings incorporate a steel frame, the steel frame will provide a good connection with the earth which will effectively limit the rise of earth potential.
A PME supply may be provided to a metalclad building provided that:
a) the metal cladding is bonded to the steel frame.
b) the supply is either:
three-phase with less than 40% unbalance, or single-phase, provided the frame to earth impedance is less than 20 ohms.

I suppose if the above isn't met, then TT for both buildings would be the obvious choice?

 

[timhoward]

Section 717 is worth a read