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Exporting PME to Socket in high street.

M.L.R

Hi All

First time question,

On doing a EICR on a feeder pillar, in a shopping pedestrian high street. Which controls decorative floor recessed lighting and also Ceeform Socket in manholes in the floor. They access sockets by lifting the lid and then plugging into them. They are market traders that use the outlets and plug in various items small and large Class 1, one of the largest items I have seen plugged in is a Stainless steel Fish counter on wheels, Bake potato ovens on steel benches ect. 

The earthing arragement is TNC-s. The panel was contructed by a well know high street furniture panel maker. Wiring may have been done by others. This is a unkown.

All lighting are on MCBs

All sockets on RCBOs 

So I have failed/or going to fail the installation due to exporting the PME to the socket outlets and for others reasons.The reason for this was,upon reading the (Guide-to-highway-electrical-street-furniture section 6). As section 6.5 mention being supplied from a TT system. Also in section 6.11.2. On completion of the construction phase of an installation a full electrical inspection and test must be carried out to confirm that the installation complies with BS 7671 in its entirety but especially to Part 7, Section 708 – Electrical installations in caravan/ camping parks and similar locations as applicable.(aiming this should be TT)

Just for clarifiction, am I missing something.As I could not see the manufacture doing this! If they did do it or I'm missing something. 

If this is true and should have been TT, then raising another issue if changed there could be  2 earth arrangments within arms reach within the High street.Thats for another day.

Look foward to your Input.

Cheers

Mark

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  • 0

    Tricky. It sounds like what gets plugged in aren't exactly caravans - so aren't necessarily legally banned from using PME Earths like real caravans (and boats) are by the ESQCR. These sockets sound more like "Highway power supplies" - so more likely fall under 714 - which doesn't have any blanket PME prohibition (at least in BS 7671 itself). I'm not familiar with the guidance you mention unfortunately.

    As you say, constructing a TT system in a busy high street isn't simple of itself - not only the issue of other items within reach (lighting columns, street signs etc) being on PME, but positioning the TT electrode so it's sufficiently distant from any metalwork in the ground connected to PME (e.g. including the sheath/armour of buried cables and bonded metallic gas/water pipes) not to be influenced by any rise in potential on the PME system could well be "challenging".

    I suspect the risks are typically lower than for a (worst case) caravan too - less bare soil and bare feet - shoes and tarmac can be reasonable insulators for example.

       - Andy.

  • 0 in reply to AJJewsbury

    It is a publication from The IET, chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/electrical.theiet.org/.../guide-to-highway-electrical-street-furniture.pdf  Cheers for the reply

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