EV charging via Commando socket - wiring regs

[poiuytre111]

I am investgating AC EV charging at my property and the wall nearest to the parkng space has recently been rewired and is served by a new CU but sadly no spare MCB positions. I like the look of the Type 2 / 16a Commando leads which allow charge rate setting (and current limiting) up 10, 13 or 16A and which include RCD AC and DC detection and charge initiation delay in 1hr increments. Before bringing the electrician back I was just wondering what the simplest regs-acceptable approach might be to connect to such a lead and, in particular, if I will need a new CU. I know it is possible to add a dual 13a socket fed through a 2.5mm Twin & Earth cable from an existing 30a ring but do the regs allow addition of the same but with the dual 13a socket replaced by a single 16a Commando socket ? Otherwise I would expect it to be feasible to either replace the Commando plug on my charging lead with a 13a domestic plug in typical granny-cable fashion or possibly create an adapter to go between a Commando socket and a 13a plug - neither of these would strictly need the electrician since the domestic wiring would be untouched but the resulting granny cable would be current constrained by the 13a plug.

 

[Adam_151]

I like the look of the Type 2 / 16a Commando leads which allow charge rate setting (and current limiting) up 10, 13 or 16A and which include RCD AC and DC detection and charge initiation delay in 1hr increments.

Bare in mind, that if you limit yourself to 16A, its not much faster than a 'granny charger' lead. I know most of the latter limit themselves to 10A rather than 13A, but 16A is roughly 3.5kw. The likes of octopus go give you 4 hours of cheap rate charging each night, thats 14kwh per night or roughly 50mile range added during each nightly cheap period, is that going to be enough?

Personally if you were going to the trouble of having a commando socket fitted for a mode 2 charger than you'd probably want to go for 32A IMHO

Before bringing the electrician back I was just wondering what the simplest regs-acceptable approach might be to connect to such a lead and, in particular, if I will need a new CU.

Issues are:

Unshuttered sockets such as commandos shouldn't be installed in domestic or similar premises, personally I'd be happy enough with an interlocked version of the socket as I feel that gives equivelent protection, others views might vary

#1 If the socket is intended for charging a vehicle then it needs to either have PEN protection or be on a TT rather than TNCS earth, if the mode 2 charger has built in pen protection, then how do we stop it being changed to one that doesn't?

#2 If the socket is intended for charging a vehicle then it must not be downstream of a type AC rcd, ideally it shouldn't be downstream of a type A rcd that serves significant other loads, Even a type A RCD is not good enough if the mode 2 charger doesn't have DC fault protection

#3 If the socket is intended for charging a vehicle then it should have its own individual RCD protection, which should be double pole, you can argue that its built into the mode 2 charger, and the one before the socket doesn't therefore need to be DP, but again, it might be swapped out to something different

I know it is possible to add a dual 13a socket fed through a 2.5mm Twin & Earth cable from an existing 30a ring but do the regs allow addition of the same but with the dual 13a socket replaced by a single 16a Commando socket ?

Generically - no, for EV charging - Absolutely not!

No, 13A plugs have 13A fuses in to protect the leads on appliances, equiment with a 16A commando connector is designed with the expectation that the upstream cirucit protetcion is 16A (or at worst 20A). Note that you can't put a 32A socket on the ring either!

To summerise:

You'd be better off with 32A rather than 16A.
There is no way around having a separate circuit for it
To do it properly you'd want a dedicated double Pole RCBO (or RCD paired with MCB), PEN protection and an interlocked socket.
You'd probably just be better off getting one of the wallbox style chargers

 

[Murdochcat]

A 2nd / new cu are the only logical solutions

 

[poiuytre111]

Thanks for the replies, no great surprises but the confirmation is useful. I think the key issue is that the outlets on the ring circuits as we use in the UK need individually fused plugs because the ring fusing is set at a multiple of the single outlet rating and the Commando plug is not fused.

 

[JohnW2]

I think the key issue is that the outlets on the ring circuits as we use in the UK need individually fused plugs because the ring fusing is set at a multiple of the single outlet rating and the Commando plug is not fused.

Indeed, and that issue isn't just restricted to "UK rings" - it's equally true of radial circuits. It's somewhat 'worse' with UK rings, since a special dispensation in the regulations then allows the circuit to be protected ('fused') by a device that theoretically is not adequate to protect the cable of the circuit (e.g. a 32A MCB protecting a cable with a 'current-carrying-capacity of potentially as low as 20A).

Kind Regards, John

 

[Taylortwocities]

You say your “new” CU has no spare MCB positions. Post a photo of the CU do we can see the MCBs and the labels. We may be able to suggest a way to free up a slot.

 

[ericmark]

A fuse works by melting, so clearly it produces some heat, the problem with the 13 amp plug is changes from the original design with insulators on the live pins means it can't transfer the heat into the socket as easy any more, so at max rating over an extended time the plug can over heat, so the typical granny lead is 2 kW not 3 kW due to the extended time it is on charge for.

I don't have the latest edition of BS 7671 and I hear people say we should not use commando sockets with domestic, however nearly every caravan and boat are supplied by commando sockets, and they are domestic, so some thing does not ring true. The idea of a 32 amp commando socket seems good, as it can not only supply an EV but other items like welding sets, however the problem is the use of TN-C-S supplies, and the possibility of DC freezing a RCD.

So we need two protective devices, one is loss of PEN detection, and disconnection and the other is 6 mA DC detection and disconnection, many of the leads incorporate the 6 mA DC detection, but the loss of PEN seems to be only included with fixed EV charging points.

Be it 2, 3, or 7 kW the loss of PEN is the big problem. The idea of the granny lead is for emergency charging when away from home, and it seems doing a risk assessment the chances of there being a loss of PEN at the same time as using the emergency charging lead are low, so some one it seems feels we can take a chance, and I have used class I items in my garden from time to time, like the standard car battery charger. Although the ones I have now are class II.

The other option is a TT supply, but banging in earth rods also comes with problems, not really a DIY job, the IET supply to outbuildings does go into some of the problems. I have included links mainly to show how complex, rather than expecting you to DIY the work.

If the whole car, or caravan is inside a building which is itself bonded then the loss of PEN is not a problem, so using the granny leads in a garage is not a problem, so a 32 amp commando socket in the garage so both welders and car charging units can be plugged in makes sense, and maybe the granny lead is intended for use in a garage?

The use of type A rather than type AC RCD's is required, however any new installation today can't use type AC anyway, but the 6 mA is not much, and only EV charging leads seem to have DC detection, and other items also produce DC like the three port valve used with central heating, without looking at faults with LED lighting etc. I take the attitude which maybe wrong, that with 14 RCBO's (RCD and MCB combined) that the chances of earth leakage and DC injection at the same time on the same circuit is slim, and the RCD part of the trip is secondary protection anyway, so even with type AC RCBO's I am not really worried.

This is also a point with EV charging, if the charger is the only item supplied from that RCD then the chances of both DC leakage and an earth fault at the same time is slim, although not impossible, however you would not want the EV charger to be supplied by the same RCD as other items in the home, as it could be rendered inoperative, not only by the EV but also other items in the home. So the EV charging point needs its own dedicated RCD, so this rules out any idea of supplying it from the ring final.

If you consumer unit is using two RCD's feeding so many MCB's each, then by moving to RCBO's it also frees up 4 slots, so room for the dedicated supply to the EV charging point, and even room for a SPD too. However the cost of a shell of the consumer unit is so little compared with cost of RCBO's that go in it, likely cheaper to swap whole consumer unit anyway as you can then select one of the cheaper makes.

I realise that the idea that if some one can afford an EV vehicle they can also afford the EV charging point does not really work where the EV is provided by the firm you are working for, however the cost of EV charging points should be taken into consideration before making the change. I look at the homes in this village, and 90% don't even have a drive never mind a garage, a car park has been built for people to park their cars off road, but there are just two EV charging points, both 22 kW but switched off at night due to abuse. So most people in this village an EV is a non starter. I am one of the few who can park my cars off road, as long as it has a reasonable ground clearance, can't get Jag XE into main parking area at back of house as it grounds.

 

[JohnW2]

I don't have the latest edition of BS 7671 and I hear people say we should not use commando sockets with domestic, however nearly every caravan and boat are supplied by commando sockets, and they are domestic, so some thing does not ring true.

I'd have to have a little hunt for my older editions, but does the one you have not include something like this ....

53.1.201 Every socket-outlet for household and similar use shall be of the shuttered type and, for an AC installation, shall preferably be of a type complying with BS 1363.

?? As has been said an 'interlocked' commando socket is probably 'just as safe' as a shuttered one would be (although not strictly compliant with the above), but a 'simple' commando socket would certainly not be compliant, any more than an unshuttered BS 546 one would be.

.... however nearly every caravan and boat are supplied by commando sockets, and they are domestic, so some thing does not ring true.

As for that apparent anomaly you have identified, note that the above reg does not talk of "domestic" but, rather of "household and similar use" and I'm not sure that would necessarily include caravans. Indeed, even if it did say "domestic", BS 7671 does not define that term,so we still wouldn't know what they intended.

Kind Regards, John

 

[plugwash]

IIRC BS7671 also doesn't define shuttered.

 

[JohnW2]

IIRC BS7671 also doesn't define shuttered.

That is correct. However, whatever the intended meaning ,I can't really see how a 'simple' commando socket could possible qualify as 'shuttered', can you?

Kind Regards, John

 

[plugwash]

IP44* "commando" sockets have a spring loaded flap which covers the contacts when not in use. This is clearly a step up compared to an unshuttered BS546 but a step down compared to a BS1363 or shuttered BS546. Is it sufficiant to count as a "shutter"? who knows!

Something I wonder but haven't been able to find good information for, is there an age of child where their fingers are both strong enough to open the sprung flap and small enough to stick in the resulting holes.

* IIRC theoretically there exists and IP20 version of IEC60309 but I've never actually seen one in use.

 

[JohnW2]

IP44* "commando" sockets have a spring loaded flap which covers the contacts when not in use.

They do.

I now see why you mentioned the lack of definition of 'shuttered'! All I can say is that I wouldn't personally think that was within the spirit of what most people probably think of as 'shuttered'.

Something I wonder but haven't been able to find good information for, is there an age of child where their fingers are both strong enough to open the sprung flap and small enough to stick in the resulting holes.

I would imagine that a very small child could probably open the flap if they wanted to, since the springs are pretty weak. Even newborn babies can 'grip' fairly strongly!

As the IP44 implies, those sockets are pretty well protected against the insertion of fingers, even of a small child, the live L and N (but not the E) parts been way down a 'long dark narrow hole' in the plastic. However, I'm not sure that is necessarily enough, because a child (or adult!) could, if they so wished, easily insert a metal object which could make contact with live parts.

* IIRC theoretically there exists and IP20 version of IEC60309 but I've never actually seen one in use.

That presumably would be potentially 'dangerous'. I'm certainly not a small child but, despite the implication of IP2x, even I can get most, if not all, of my 'little finger' through a 12.5mm hole - so if the 'long dark hole' was anything like that big, I'm sure that some children could get their fingers in! What I don't understand is why anyone would see a need for an IP20 commando socket, since the 'standard' IP44 ones don't need to have any wider a 'long dark hole' than they have!

Having said all that, I have at least a couple of such sockets (in outhouses) and am perfectly comfortable wit that, even if there are small children around!

Kind Regards, John

 

[plugwash]

An IP44 or IP67 commando socket is only IP4x because of the flap. Without the flap it wouldn't meet IP4x or IP3x so it would be IP2x.

Phase/Neutral pin diameters in IEC60309 seem to range from 5mm for the 16A version to 10mm for the 125A version.

Remember IP2x doesn't mean "has holes exactly 12.5mm in size", it means "has holes that are bigger than 2.5mm and smaller than 12.5mm.

I believe the difference with the IP20 variant was it had a retention clip instead of a flap. Presumably it was intended to be slightly cheaper, but it never caught on.

 

[JohnW2]

An IP44 or IP67 commando socket is only IP4x because of the flap. Without the flap it wouldn't meet IP4x or IP3x so it would be IP2x. Phase/Neutral pin diameters in IEC60309 seem to range from 5mm for the 16A version to 10mm for the 125A version. Remember IP2x doesn't mean "has holes exactly 12.5mm in size", it means "has holes that are bigger than 2.5mm and smaller than 12.5mm.

Good and valid point, which I was overlooking.

However, it seems more than a little odd that something which would otherwise be IP2x can become IP4x (let alone IP6x) by virtue of a sprung lap which, as I said (certainly for 16A ones) could probably be easily open by a pretty small child ("without use of a tool", as some would say!), isn't it?

After all, such an easily-opened sprung flap would surely not be acceptable as a means of making any enclosure IP4 (or higher) if it would otherwise be (with the flap opened) IP2x (or even IP0x !), would it? If not, if that's true of an enclosure, why should a socket be different?.

I believe the difference with the IP20 variant was it had a retention clip instead of a flap. Presumably it was intended to be slightly cheaper, but it never caught on.

Maybe. Like you, I've never knowingly seen one in use - and I'm not sure that I even knew that they existed.

Kind REgards, John