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Topic Title: .Installation of electrical charging point on PME supply .
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Created On: 03 April 2017 04:56 PM
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 03 April 2017 04:56 PM
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AdamKuzack

Posts: 12
Joined: 07 March 2017

Facts
Supply is PME
Electrical charging point to be located outside in the porch. Car will also be charged on the porch / driveway.

Regulation Section 722 general rule is that for Electrical charging point which is to be located outside PME supply should not be exported and either a) separate earthing electrode installed or b)isolating transformer.

However section 722 does allow exceptions to this in a dwelling where it is not reasonably practical for electrode to be installed .

Customer does not want earth electrode and would cause major disruption as new porch and house .

Can I make this an exception and not install electrode and export PME. I have assessed the porch and only metallic parts that are liable to be simultaneously touched is the gas pipe which I intend to cover with insulation foam and to cable tie.

Need views and opinions on this
 03 April 2017 11:29 PM
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mapj1

Posts: 9362
Joined: 22 July 2004

what will customer be standing on when he or she touches the car. If the floor is cement you could embed a grid and bond that to the PME earth. May be more hassle than an electrode near porch, or at CU and full house TT.

Or you are looking at a 3 pole VOELCB - do they actually exist yet?

-------------------------
regards Mike
 04 April 2017 08:28 AM
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AdamKuzack

Posts: 12
Joined: 07 March 2017

Thanks Mike,

Specifically, I was looking for clarification on the exception within the regs with respect to a dwelling. It would be a cause of major disturbance to install an additional earthing electrode or a grid etc and I think the requirement is to get this to a touch voltage of 70, it may require multiple earthing electrodes to be installed . would it be advisable to export PME and to insulate any simultaneously accessible parts, or is the position that you would not touch this with a barge pole if the electrodes were not installed .
 04 April 2017 09:56 AM
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AJJewsbury

Posts: 15835
Joined: 13 August 2003

It's usually not too difficult to install an electrode, even if the exterior surfaces are hard surfaced, at worst it should be possible to drill a hole through the surface layers and then bang a rod in. I'm not convinced 'customer not wanting a rod' really equates to 'not reasonably practical'.

If you TT the charge point, the rod would only have to achieve a normal sort of resistance (ideally <200 Ohms) rather than the miniscule figures needed to limit PME to 70V on perhaps a 100A max demand installation.

insulate any simultaneously accessible parts

Consider Mike's point that outdoors, the surface of the ground can provide a potential (generally an earth potential), not just metallic parts.

gas pipe which I intend to cover with insulation foam and to cable tie.

Foamed plastic type pipe insulation isn't particularly long lasting outdoors given the rigours of weather, UV radiation and physical impact - I'd personally be looking at something a bit more robust - perhaps something like: http://www.meterboxesdirect.co...pipe-cover-63-mm.html
- Andy.
 04 April 2017 01:06 PM
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AdamKuzack

Posts: 12
Joined: 07 March 2017

Once again chaps, thank you for the advise and the insightful comments.
 04 April 2017 09:25 PM
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mapj1

Posts: 9362
Joined: 22 July 2004

What is the ground like, and where in the country are you - to trip a 30ma RCD - the TT island requirement, a single 4 foot rod is probably enough.
Note that it is possible to slant drill out through a wall, and put a rod in at 45 degrees or similar jaunty angles if need be to reach terra-firma proper from inside a building witha thick floor slab.
If you try this and seem to be drilling a damp course, always bad, then tar paint of the type sold as car underseal or flat roof repair, can be glooped in to line the hole to restore some integrity for the damaged section , and helps to prevent damp patches/ blown render etc. Its horrible stuff if it gets on your trousers though.

-------------------------
regards Mike
 05 April 2017 05:03 PM
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sparkingchip

Posts: 9953
Joined: 18 January 2003

"Customer does not want earth electrode", the customer will not be signing the certificate as the designer.

"Would cause major disruption as new porch and house", I can't imagine it would be too much work to make a tidy job.

Andy B
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