Should the fence be earthed?

Question

I've been asked to design a car park lighting scheme but the site owner insists on mains luminaires attached to his perimeter fence which is powder coated steel similar to Jacksons Euroguard. My instincts tell me the fence should be earthed but I would be grateful for the views of forum members.

AJJewsbury · Accepted Answer

Colin Johnson said: My instincts tell me the fence should be earthed 
 I'd say no need to earth the fence - as it shouldn't be an exposed-conductive-part (if the fittings are class I they should be earthed themselves anyway (and if Class II it shouldn't matter). Hopefully your wiring system won't be liable to directly make the fence live if basic insulation failed (e.g. in conduit or sheathed/armoured cables). 
 The fence might want to be bonded though, as an extraneous-conductive-part. It's not clear cut though - bonding in general is no longer mandatory outdoors these days (411.3.1.2), and there has been a long standing regulation for outdoor lighting that "A metallic structure (such as a fence, grid, etc.), which is in the proximity of but is not part of the outdoor lighting installation need not be connected to the main earthing terminal" (714.411.3.1.2). We can debate whether attaching lights to a fence makes the fence part of the lighting installation, or is merely a support for it. Other design considerations might suggest that bonding might be a good idea though - e.g. to act as by-pass for relatively thin c.p.c.s if large currents might sometimes be expected (e.g. from diverted N currents). Or might be a bad idea (due to touchable potential differences - e.g. another fence within reach...). Often there's no one simple right answer, just a least worst. 
 - Andy.

GTB · Answer

Colin, 
 You dont mention what type/size/weight of luminaires to be placed on the fence, nor indeed height from the ground. 
 As mapj1 mentions consideration required with regards vandalism both to Luminaires but also how the cable is fixed etc to the fence. 
 My other thought is wind loading on the fence which will depend on fitting size and weight, so how many fittings etc, also has the efncing contractor been informed that luminaires have to be installed on the fence? They may have an opinion on that as well. 
 Cheers GTB

gkenyon · Answer

The fence is not part of the electrical installation. As Andy Jewsbury said, protective bonding of extraneous-conductive-parts now (and, for some very long time, back to 16th Edition) only applied to each building. 
 Whether you should use Class I or Class II luminaires is a good question. 
 You see, there are cases where you need to NOT connect fences to an LV electrical installation ... for example, if near or associated with an HV substation, or electric railway (in these specific cases, you can end up with HV on your LV system).

Chris Pearson · Answer

Euroguard seem to be fence panels, so how are they supported? 
 If the supports are steel planted into the ground, the situation may be different from say, concrete posts.

Should the fence be earthed?

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