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Hello,

I have a plug in hybrid car and to triggle charge this at 10A, I would like to extend a simple UK 3 pin 13A outside socket from my kitchen ring main 32A TN-C-S supply as a 13A fused spur. The ring main is further protected by a 30mA RCD.

I'm a little confused by the change due to the 18th edition regulations. Should I provide a local earth spike with impedance below 200Ohm near the outside socket (20m away from the house) and if so should this now have a local RCD with earth solely from the local earth and be seperated from the earth to the supply from the house?

I just want to be sure I interprete this correct before asking an electrician to sign off on my handywork.

All comments welcome

Marc
 

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Strictly speaking, the outside socket if it is a designated EV outlet, should be on a dedicated circuit (radial, possibly 4mm2 depending on how the cable is insulated or not). From a practical point of view, it would be easy to overload the kitchen ring main with the car charging (eg high power kettle, toaster, electric fryer washing machine ?etc), no diversity should be applied to the car charging.

The RCD requirements are different for the inside and outside EV charging duties so another reason why the circuits should be split.
 

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As Above.
Ring mains can cause problems behind the sockets if there is a poor connection. Unlike other appliances, cars draw high currents for hours on end and will show up any wiring weakness. .

The need for an earth rod is one I've wondered about as I'll need power to a greenhouse for a propagator (22w double insulated + possibly a light), Not Car related but it is down the garden.(n)
 

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First off, an electrician should not inspect, test and sign off on a Part P notifiable installation that they haven't installed, or at least been able to inspect all hidden wiring runs etc. The electrician is going to have to lodge the EIC for the Part P notification in their name and using their accreditation. I'd not have risked doing that for notifiable work done by someone else, TBH.

As above, although it's fine to run a 13 A outlet from a spur off a ring final, it's not really wise if you know that the spur isn't going to have the normal diversity allowance applied. Better to run a dedicated radial, with its own protection, both in terms of reducing the risk of overload and, perhaps more importantly, possible nuisance tripping on one of the house circuits.

The need for a TT island for external supplies has been around for a long time, although it hasn't usually been specifically applied to household outbuildings on relatively short cable runs. It has applied for years for things like outlets used to power caravans, though. It's a matter of judgement as to whether a greenhouse supply should run with a PE exported from the main supply, or be connected as a TT island, although if it's a metal greenhouse consideration should be given to bonding the metalwork. If it were me I'd just assess the risk based on the specific circumstances.

For example, my workshop/garage is the opposite end of our garden from the house, with a ~30m run of 6mm² SWA supplying it, protected with a 40 A DP MCB and with the armour connected only to the TN-C-S PE, not the workshop PE. I opted to install an earth rod and wire the workshop as a TT island, simply because I personally didn't like the idea of exporting the PE down 30m of cable. The regs don't mandate this, but I felt it was a slightly safer way to do things.
 

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The RCD requirements are different for the inside and outside EV charging duties so another reason why the circuits should be split.
I never understood this, it is far too vague and ambiguous, my charger is inside the garage but I can charge it just as easily outside on the drive, in my opinion even though my charger is inside it should be treated a being outside but that probably creates a different problem.
 

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By the same token, anyone can run an extension lead outside from an outlet inside. It comes down to the definition of installed equipment, and a portable lead isn't installed equipment, but the fixed EVSE box is.
 

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By the same token, anyone can run an extension lead outside from an outlet inside. It comes down to the definition of installed equipment, and a portable lead isn't installed equipment, but the fixed EVSE box is.
I put my own 32A charger in at my friends workshop, its inside and its not fixed, in the process of installing a 32A charger in my garage by repurposing a redundant shower circuit.
 

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I put my own 32A charger in at my friends workshop, its inside and its not fixed, in the process of installing a 32A charger in my garage by repurposing a redundant shower circuit.
OK in terms of meeting the letter of the regs and the law (Part P) if it's portable and not permanently wired, but connected to an installed 32 A outlet. The 32 A outlet is fixed equipment, though. Whether it's notifiable under Part P depends on the location and whether or not it's an "existing circuit".

When I wired this house I knew that I wasn't going to be able to sign off on any new circuits that were added after the EIC was lodged (sadly the old NAPIT Just 8 scheme for retired bods seems to no longer exist) so I ran extra circuits wherever I thought I'd need them, terminated in suitable enclosures. This means I can legitimately add new kit without needing Part P notification, the next installation will be a battery storage system and inverter/charger, for which I've already got two runs of SWA running to an IP65 box where the "battery shed" is going.
 

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OK in terms of meeting the letter of the regs and the law (Part P) if it's portable and not permanently wired, but connected to an installed 32 A outlet. The 32 A outlet is fixed equipment, though. Whether it's notifiable under Part P depends on the location and whether or not it's an "existing circuit".

When I wired this house I knew that I wasn't going to be able to sign off on any new circuits that were added after the EIC was lodged (sadly the old NAPIT Just 8 scheme for retired bods seems to no longer exist) so I ran extra circuits wherever I thought I'd need them, terminated in suitable enclosures. This means I can legitimately add new kit without needing Part P notification, the next installation will be a battery storage system and inverter/charger, for which I've already got two runs of SWA running to an IP65 box where the "battery shed" is going.
The 3 phase socket was already in the workshop so its just like any other 3 phase equipment except I'm only using one phase :) likewise with the shower circuit just moved the wires to a fuse box, the charger will be on a 32A plug so its portable equipment.

Like I said the regulations are a bit ambiguous.:confused:
 

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Frankly the law is a real mess when it comes to electrical installations, it should be clear-cut, like gas regulations. BS7671 is only guidance, so there's no compulsion for anyone to follow it to the letter, and mixing up electrical safety with building regulations, just so that a Statutory Instrument can be partially applied, is ambiguous at best, and really just a money-making scam for the various competent person schemes, IMHO.

I'm in the ludicrous position of being a competent person, so I can do any non-Part P notifiable work, including inspection and test on any domestic electrical installations (which involves disconnecting wires inside the distribution board and working near live terminals) and I can legally issue an EICR.

However I'm not deemed competent to run a cable to an outside socket on an existing electrical installation now (despite having been deemed competent to do this before I retired) because I'm no longer eligible to be a member of one of the competent person schemes, just because I'm retired.

Years ago I had a part-time evening job teaching electrician apprentices electrical engineering science at college, and a day job managing a Notified Body under the LV and EMC Directives, plus, even though I was retired, I was legally allowed to wire our new build house recently (didn't need the new installation undertaken by a Part P competent person as it was already subject to building control inspection...).

The whole thing is a bit of a shambles. Given that NICEIC, Elecsa, NAPIT, STROMA etc all make a nice little profit from collecting hundreds of pounds in membership scheme fees to allow Part P EICs to be lodged on the database, I can't see anything changing.

Even dafter is that if we lived in Scotland none of this nonsense would apply, as they don't have Part P up there, so I'd magically become competent again...
 

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The workshop installation, CM charger below distribution panel and you can just see the socket it's plugged in to.

20190211_112650.jpg
 
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