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RCD for outdoor public Car Park high mast lighting

Gyaneshwar Kumar

Hi all,

Hope you're doing well.

I'm working on a project where we're installing a number of high mast floodlights and lighting columns (6m high) in a big public car park. I'm trying to determine whether these lighting circuits require RCD protection.

BS 7671 isn't entirely clear on this. It states that lighting accessible to the public requires RCD protection, but it also specifically excludes street lighting, so I'm not sure which category this installation falls under. Also, technically  there's the need to balance the use of RCD against the risk of nuisance tripping.

Have you come across a similar situation before, or do you know how this is typically approached?

Thanks for you help.

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  • 0

    There is also this incident

    https://www.ioshmagazine.com/2026/06/30/leisure-operator-fined-after-footballer-dies-electric-shock?__cf_chl_f_tk=5euAeUHR7_Tg3n6wcP2w2U2U.OwYVY.hjmxbSZfTDCg-1783444929-1.0.1.1-XmorwJf5wxDXIBHWt8SsNcIpH_RTUaNj4PFACXfP3oU 

    Which was put down to poor maintenance and not resolving a known problem, but presumably if there had been an rcd in place, even if it was 500mA it would probably have tripped and prevented the incident.

    Is there some justification for finding the maximum resistance to earth for the lamp posts (presumably reasonably low, but not low enough to trip on overload) and having a protective device that trips before said lamp post reaches 50V? It wouldn't be tripping at 30mA but significantly improve safety for people touching the lamp post.

  • 0 in reply to Alan B
    Alan B said:
    Which was put down to poor maintenance and not resolving a known problem, but presumably if there had been an rcd in place, even if it was 500mA it would probably have tripped and prevented the incident.

    Another interesting one ... which begs the question quite where and what was the fault and where would the RCD have been placed? 714.411.3.4 only seems to ask for 30mA RCD protection for the lighting itself - rather than the steel column that's holding it up. So, especially where the supply is looped from one column to the next, you might well expect see RCDs in the base of each column ... so if the fault is upstream of that point the RCD may or may not be of much help. 500mA ones may or may not trip before the victim makes contact - all depends on how much of the c.p.c. is left or if there's some other path to earth (steel columns in the ground might seem like they'd be their own electrode, but the roots are commonly painted with bitumen paint to reduce corrosion and/or planted in plastic sleeves to limit damage to structures during future replacement, so nothing is reliably guaranteed) - in the case of direct contact or similar when practically all the fault current goes through the victim a 500mA device is perhaps unlikely to trip at all as body resistance alone (often circa 1kΩ) will often limit the residual current to below 250mA - maybe less when footwear, ground coverings, dirt or paint layers are taken into account.

       - Andy.

  • 0 in reply to AJJewsbury

    Didn't think about the base of the columns being protected. That makes things more challenging without a good path to earth.

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