Exported PME to steel floodlight columns, public tennis courts

AJJewsbury said:

Where the lighting columns are supplied from a conventional installation that might have loads of tens or hundreds of amps (after the single N-PE bond) - a 20Ω electrode or two are going to provide negligible safety benefit.

True, but if the hundreds of amps was actually in the form of lots of floodlights each with a 20 ohm electrode, or indeed a street of houses each with an earth bond to many metres of water pipe serving as a horizontal electrode, whether or not those then meshed together to form a neutral "conductor of opportunity", then it starts to look less shaky. That is the whole PME premise, and works quite well in built up areas - and during a fault  the surface step voltages are limited by paving, and electrodes do not generally come to the surface. It is less suited to wet mud, overhead singles and small transformers whose own earth electrodes may approach that 20 ohms - it is possible in the small substation case to have a fault from live to true terra firma earth that is lower resistance than the official neutral to terra-firma electrode(s), so the neutral 'centre' of the 3 phases gets pulled significantly off earth - also not ideal but safer at the point of fault - but at the price of being more dangerous somewhere else...

There is a tendency for some to pooh-pooh TT, rather like the old ring final, as being a bit last century, and that is not really correct either.

M.

True, but if the hundreds of amps was actually in the form of lots of floodlights each with a 20 ohm electrode,

Doesn't seem likely in the OP's case though - we're told it's a "local tennis club" - so I'm guessing there's a club house, changing rooms, showers, bar etc. and the floodlights have been tagged onto the main installation rather than receiving their own DNO supply. If that is thee case then while the floodlights might appear superficially to be similar to street lighting, in terms of sensible earthing precautions they're in a different ball park,

   -  Andy.

Different ball park?

The guy in the news report linked to above died in a ball park with lights on high columns.

Yes, in that instance lack of maintenance appears to have been an issue and in the pub garden substandard installation was an issue, but the Wiring Regulations have been revised since these incidents, partly due to what happened.

Do we have any idea what went wrong?

Might it have been a fault which was not cleared by ADS? A faulty RCD?

The Regulation 714.411.3.3 in the 18th Edition has been expanded and become 714.411.3.4 in the 18th Edition Amendment Two, broadening the requirement for 30 mA RCD protection to include gardens, spaces open to the public.

Yes, I would agree with you Sparkingchip. Strict reading of the regulation would require 30mA RCD protection for the tennis court lighting. After all they are in a space open to the public. Not sure if that was the intention but that’s neither here or there. 

30 mA RCD protection is an absolute requirement for lighting in a pub garden, there’s no way anyone could argue that it doesn’t come under indent (i) Gardens, spaces open to the public.

I am fairly confident that the requirement covers a tennis club and courts as well.

30 mA RCD protection is an absolute requirement for lighting in a pub garden, there’s no way anyone could argue that it doesn’t come under indent (i) Gardens, spaces open to the public.

I am fairly confident that the requirement covers a tennis club and courts as well.

But it's not an absolute requirement as stated - it's conditional on the lighting being accessible and not of the kind listed as excluded (which includes street lighting). It still seems to me that a light fitting on the top of a 5m or whatever pole isn't accessible to the public. The pole itself, even it metallic and bonded, isn't any more hazardous than any exposed- or extraneous-conductive-part and I don't see any additional protection being demanded for outside taps.

   - Andy.

Thank you everyone and this has been a really useful thread for me. As way of a post script I spoke to NIC tech today about this. 

Just to answer an earlier question, the light supply is not direct from a DNO and is distributed via the 3phase feed at the club house

Some debate about whether it was in the excluded from list of public lighting that needs the 30mA RCD but the only exclusion that came near was street lighting and traffic signage. Obviously not that, so was deemed to be spaces open to the public so required additional protection. I think we can agree on that?

Other debate as hilighted by Mr Jewsbury was would the light high on top of the column be accessible to the public, however we quickly agreed that the metal column had to be included as part of the light. 

What we couldn't decide was the EICR code. C3 improvement recommended because the installation met the regs at the time it was installed  (10 years ago) or a C2?

One none compliance that nearly passed me by and (had to read it twice) was 714.411.201the door in the street furniture used for access not to be used as barrier or enclosure. This installtion had an unenclosed din rail with MCBs screwed to a metal plate in the column, so C2 for that anyway.

This has been a learning journey , thank you and now we are going to become  floodlight specialists just to annoy David Stone

Cheers Pat

714.411.3.4 has made its way onto the NAPIT domestic installations EICR Schedule of Inspections, so I have already found myself questioning it’s scope.

engx.theiet.org/.../129635