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Topic Title: 18th Regs - Electric Vehicle EVSE (Charging Point) RCD Requirement
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Created On: 03 November 2018 05:07 PM
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 03 November 2018 05:07 PM
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martinwinlow

Posts: 9
Joined: 24 May 2015

I am given to understand that as of Jan 1st 2019 the 18th edition of the Wiring Regs stipulate that *all* electric vehicle charging points (EVSEs) must be protected with a 'Type B RCD" where the 'Type B' relates to the sensitivity of the RCD to ac, pulsating ac *and steady dc leakage currents*.

Assuming the above is correct, would anyone care to suggest a source for 2-pole and 4-pole 16A and 32A RCBOs that comply with the above which won't, at a stroke, *double* the cost of an EVSE?

Martin Winlow.
 03 November 2018 05:20 PM
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gkenyon

Posts: 5354
Joined: 06 May 2002

It's worth reading Regulation 722.531.2.101 carefully.

Some charge point equipment has some protection against DC fault currents above 6 mA built in, so Type A may be appropriate for that equipment.

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 03 November 2018 05:37 PM
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martinwinlow

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Thank you for your reply. In my experience, built-in DC fault current protection is rare but I have only dealt with the domestic and relatively low-power output industrial EVSE market.

I am concerned that the imminent 'Type B' stipulation is a classic HMG hopelessly ill-conceived overkill/over-reaction to a near-non existent problem. I should not, of course, be surprised as OLEV's idea of 'supporting' the EV-charging market has been spectacularly mismanaged, with hundreds of millions of tax-payers money scandalously ill-spent.

But... back to my original question. If these Type B RCDs (preferably RCBOs) *are* soon to be required, where can I buy them for a sensible price? My googling produced very few options, the cheapest of which was *20 times* more than the norm for relatively common Type A RCBOs...
 03 November 2018 07:58 PM
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paulskyrme

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I can assure you that this requirement is NOT anything ill conceived.
It has been there for many years in previous editions, but, the requirement was not specific, thus it was needed for it to be made specific.
If the wrong RCD is selected then people may die.
If it had not been ignored then the explicit regulation would not have been required!
 04 November 2018 09:19 AM
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gkenyon

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Agreed Paul,

The previous Edition, BS 7671:2008+A3:2015, said effectively, fit a type B if you know there are DC residual currents exceeding 6 mA.

This meant that someone saying "I didn't know" would have been able to fit a type A, which might have been de-sensitized by the DC residual current.

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 04 November 2018 11:40 AM
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martinwinlow

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Yes, all very sensible but *if you can't buy a Type B RCBO then it's all a bit bally moot, isn't it*?!

And just how many people have been electrocuted by EVSEs so far (in the history of mankind)?! Even using Type AC RCBOs (as lots of them are)? I know you will trot out something like "One death is one too many" or something equally trite but *what is the probability* of that happening?

You both appear to be saying "Because of the *infinitesimally* small likelihood of someone being electrocuted by an EVSE that we should ban EVs altogether". This is *extremely silly*!
 04 November 2018 12:51 PM
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AJJewsbury

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And just how many people have been electrocuted by EVSEs so far

The problem isn't getting shocks from the EVSE (or EV) as such, as the d.c. current disabling upstream RCDs - so we're potentially loosing additional protection (perhaps even ADS - on TT systems for example) to large chunks of the rest of the installation - including bathrooms and outdoors.
- Andy.
 04 November 2018 12:53 PM
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mapj1

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It is, and unless type B devices become substantially cheaper, then they won't be used at the shallow end of the market.
BS7671 is not law after all, and if it is a case of just getting some charge in somehow, then some folk will realise you don't need the RCD at all, and little a box that generates the right audio tones and presents a sensible impedance will switch the car into thiking a charge point is present, drawing current.
If electric cars become popular enough, then such trick boxes will no doubt appear on the well known auction sites.
One death is far from too many, I'd suggest we need a few tens a year in the UK to warrant any kind of safety measure, as that is the 'one in a million years' per person accident beloved of the statisticians as a threshold for action not required

-------------------------
regards Mike
 05 November 2018 08:55 AM
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arg

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The practical answer here is to put the DC detection in the EVSE and continue using Type A RCDs (as permitted in 722.531.2.101). That should be a relatively low-cost addition to the EVSE, but it seems like the manufacturers have been caught napping by this change - unless we are about to see a flurry of new product announcements, or they've been silently upgrading the products without declaring a new model.

However, I am still rather unconvinced by the requirement specific to EVs - plainly there is a risk there, but is there really evidence that this risk is more prevalent in EVs than in anything else which has a DC link internally (motor drives, anything class-1 with a switching power supply)?

Conversely, the issues with higher frequency (than 50Hz) currents do cause real-life issues but don't seem to get much attention.
 05 November 2018 04:14 PM
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gkenyon

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The requirement for Type B RCD is only for chargers with BS EN 62196-series outlets or vehicle connectors fitted, not the Mode 2 "standard socket-outlet" solution.

The cables incorporate a control pilot ...

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 05 November 2018 04:37 PM
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sparkingchip

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Question is, are you installing a fully assembled charging unit that has been designed and tested by the manufacturer then sold to you with installation instructions or are you buying a plastic enclosure along with various components to assemble your own charging unit with the supplier telling you that you are responsible for the actual design and testing of the completed unit?

With a fully assembled unit the manufacturer will have selected and installed the RCD in the unit leaving the installer to specify any upfront RCD that is required based on information in the installation manual.

Buying a box of bits on the basis that you are responsible for the design of the charging unit can leave the installer having to go down the route of possibly over specifying the RCD to cover themselves.

It's far easier to install to manufacturers instructions.

Andy Betteridge
 05 November 2018 05:56 PM
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arg

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Originally posted by: gkenyon

The requirement for Type B RCD is only for chargers with BS EN 62196-series outlets or vehicle connectors fitted, not the Mode 2 "standard socket-outlet" solution.


Fortunately, a large proportion of UK domestic installs are proper chargepoints rather than commando sockets due to OLEV (and some vehicle manufacturer) grants. OTOH, a fair number of people don't install anything at all and so end up using 13A sockets which were installed without regard to section 722 at all.

It's not at all clear what kind of RCD behaviour is in many of the portable EVSE you can buy to plug in to such sockets. I've encountered some with no RCD at all (merely a label on the back telling you to only ever plug it into RCD-protected sockets), but that's probably rare. Very common on the other hand are units where the RCD function just releases the existing contactor - which is fine for small leakage type faults, but they readily weld over on a hard fault; hopefully such a fault is hard enough to achieve useful disconnection times with whatever fuse is upstream, despite the long length of cable now added....


Originally posted by: sparkingchip
With a fully assembled unit the manufacturer will have selected and installed the RCD in the unit leaving the installer to specify any upfront RCD that is required based on information in the installation manual.
......
It's far easier to install to manufacturers instructions.


Many of the manufacturers instructions I've seen specify Type A upstream, or simply direct you to select it to meet local regulations. It will be interesting to see what happens when they get round to updating them for 18th edition.

Only a few designs actually incorporate real RCDs within the chargepoint itself (although the Rolec units which do are very common). Some others do have a built-in RCD function but still direct you to fit a proper RCD upstream - presumably because the built-in one doesn't meet the full requirements of the standards required by 722.531.2.101 (for example, the built-in one is often self-resetting).
 05 November 2018 06:35 PM
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gkenyon

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All of which adds weight to the requirements in 722.531.2.101 being necessary, particularly when you consider that the link from the charger to the vehicle includes control pilot signals.

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 05 November 2018 11:06 PM
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SeanEvans

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Graham - quick question?

when you say:

"It's worth reading Regulation 722.531.2.101 carefully.

Some charge point equipment has some protection against DC fault currents above 6 mA built in, so Type A may be appropriate for that equipment. "


Im assuming that the device protection is similar to an RCMU and failed to see how from the Beama advice that an A type or otherwise can be used upstream of it from the guidance in the Beama technical bulletin RCD section page 7

That reads: "A type AC RCD should not be fitted upstream of a type A, F or B RCD as the load characteristics that the type A, F or B RCD has been selected for could impair operation of the type AC RCD" and "A type A RCD should not be fitted upstream of a type F or B RCD as the load characteristics that a type F or B RCD has been selected for could impair operation of the type A RCD."

Surely what you have suggested does not align with the advice from Beama,

Any clarity on these points would be good as I may have confused myself.


Kind Regards

Sean
 05 November 2018 11:52 PM
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mapj1

Posts: 12039
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The thinking is that if for example the building has a 100mA type AC at the incomer, and one of the many sub-circuits off that is a B type supplying a car charger, then if the load does inject DC, but not quite enough to trip the B type, the AC may be blinded to a simultaneous fault on another circuit that should have tripped it.

Actually, this advice is not based on good physics, the 6mA threshold is sufficiently low that this will not occur - to blind an AC type with DC needs to saturate the magnetic core hard enough that the AC excursion does not un-saturate it. 6mA DC will not really blind even a 30mA AC type, the most it may do is shift the trip threshold by 6mA.
60mA of DC might be a problem. The old D-lock testers used to use a significant fraction of an amp to take out the RCD core, and then could only loop test with more current surge in the same polarity. (using a thyristor, not a triac ensures single sided testing.)
the D-lock patent
And to be honest, even then, a great many RCDs still tripped with D-lock engaged.

-------------------------
regards Mike
 31 January 2019 03:24 PM
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micelf01

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Joined: 30 January 2019

I'm new to this forum.
Does 18th edition insist that a Type-B RCD and an earth rod is required with all EV charger installs, unless the charge specifically says that no DC can make it back to the AC? That's costly a type-b RCD puts a big increase on the price of an install. Anybody know of any reasonably priced RCDs

....and whilst im here, is an earth rod the only earthing solution? Are there any other options
 31 January 2019 08:37 PM
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mapj1

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Sadly it is not as simple as that. there is a whole section 722.x that covers charging of vehicles.
It does say at least an " A type", but further for outlets to BSEN 62926 a B, or an A plus a detector to shut off if more than 6mA DC is detected.

In respect of earthing, you may not use a PME earth for an outdoor charge point - I guess in a garage is OK, - which precludes the company earth of the majority of urban networks on the UK mainland.
Unless either you can provade an earth rod of resistance so low that it can carry the neutral current in fault, and keep the NE offset voltage to less than 70V, or the 'off esrth condition is detected and a 3 pole breaker removes L N and E.

realistically the requirements for electrode resistance are much more easily met with TT and a smaller electrode.

-------------------------
regards Mike
 31 January 2019 09:06 PM
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micelf01

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Thanks Mike.

Just another question you wrote that if type A is used then some other shut off needs to be used. What other shut might be used
 31 January 2019 11:11 PM
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mapj1

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Like many areas of the regs it is left open.
I imagine the expect you might design something into the vehicle charger involving a hall effect current sensor and some threshold detection.

-------------------------
regards Mike
 01 February 2019 09:13 AM
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arg

Posts: 254
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A number of the EVSE manufacturers have now woken up to this and produced new models with the 6mA DC protection internally so you can carry on using Type-A RCDs - Rolec and Zappi are two that have made press releases about it.

This does give a problem with old stock or when given the job of moving an existing unit - since these new models mean there's no new demand for type-B RCDs, they are still going to be hard to find and extortionate price when you do.

The requirement for earth rods hasn't really changed - yes, the 18th edition no longer has the "if not reasonably practicable" exemption for domestic premises, but the IET Code of Practice accompanying the 17th edition had guidance that put a very strict interpretation on "reasonably practicable". For all of the large proportion of domestic installs that claim the OLEV grant, it is a specific requirement of the grant that the Code of Practice is followed - the installer has to provide paperwork declaring that it is.
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