UK domestic 3 pin extension lead

[WannabeOwner]

For top-up when staying with friends.

Only done this once, my host had a long extension lead, we unwound it, trailed it down his drive, and put the UMC 13 AMP plug / extension socket under the car to "keep it dry" That also reduces the amount of UMC "extension" available of course.

So I'm thinking I should carry something with me instead.

Seems I could get a formed extension lead, either 1.5mm cable up to 14M (which weighs 2.18KG)

14m single socket heavy duty 13amp black extension lead

or for something longer 2.5mm cable. Shortest on that site is 25M which is maybe longer (more unweidy? 5.2KG) than I need, and it has a double socket which is more of a rain-risk.

25m double socket heavy duty 13amp 2.5mm cable extension lead

I could also get a DRiBOX, but surely that's just one more thing to cart about?

Would a 13a plug to commando socket be better? Strikes me as being better outside. Presumably my UMC would plug into that? Although no alternative use around the garden.

14m 230v 13a plug-top to commando socket adaptor

Can I (should I??) make my own? I'm thinking 2.5mm but shorter than 25M

I already have a fairly beefy reel extension (used for a commercial-grade pressure washer, which tripped our "ordinary" extension reel). Maybe I could just take that with me on the few occasions we want to adhoc-charge? Its labelled as "50M heavy duty cable extension reel 13amp 3G 2.5mm welding 7kg".

Anything in particular I should think about when choosing a socket when I arrive? (assuming there is a choice!) Any way to choose circuits more likely to be more comfortable with sustained load?

My understanding is that I'm going to get 10A / 2.3kW and around 5 MPH. Naive question I expect: why can't I get 3kW?, given that's my understanding of what a 3-bar-fire will use

I didn't buy a Type-2 cable when i bought the car, for "public charging" I think I ought to get one of those too.

Open to any other suggestions too. Thanks.

 

[arg]

There's no really good answer to this. Commercial extension leads are often made from crappy parts, but it's very hard to tell on (eg.) Amazon which ones are good and bad.

Cables for this sort of outdoor use in winter really ought to be H07RN-F (rubber) cable rather than PVC - PVC goes hard at low temperatures and can crack (and gets worse when it gets older and the plasticiser has leached out).

I like sockets that are 'real sockets' rather than moulded into the plastic housing of an extension reel (or the cheap types of 4-way block) - those are inevitably of a relatively flexible plastic so as to give impact protection on the outside, but that means the electrical contacts are mounted to something flexible too and so the contact geometry is variable and easily makes a poor connection. So I don't like the type of reel in your last picture. The sockets in your first picture are hard to tell from the photo - they certainly look similar to the worst possible kind of moulded extension lead, but there does also exist a different type of socket where the plastic is in two parts - a hard type surrounding the actual contacts to enforce the right geometry and a softer type for the outer part to give impact resistance. Clicking through your first link, I think that is a good quality supplier (they are certainly worrying about all the right things in their spec) and so are probably using the better sort of socket too.

Personally, for rough duty I like to use metal-clad sockets (as intended for wall-mount use), with a good gland for strain relief of the cable. Metalclad is good for getting rid of heat, robust, and has the hard plastic inserts for the contacts. But it is a trade-off: it exposes the earth (not ideal outdoors on a PME supply), and depending on the exact socket may be worse for water resistance. You could consider using the sort of 'waterproof' socket (ie. with a closeable lid) that's sold for outdoor sockets, but the trouble with enclosing it is that keeps the heat in, and with 13A plugs there's a lot of heat coming from the fuse that needs to be got rid of (hence my like of metalclad). I also like, for the same reasons, the old MK 13A plugs made of hard thermosetting plastic rather than ones in your photos that are more flexible - but again it's a trade-off as these are more fragile, though at least that means they get obviously cracked and in need of replacement rather than getting bent out of shape and going slightly squidgy as they get warm.

Your suggestion of a commando socket is better in some ways - these are available in IP66 (waterproof) versions and don't have the problem of the heat from the fuse, but what do you plug into it? The commando adapters on the end of the Tesla UMC aren't IP66 so you don't gain the waterproofness even if you use that style of socket (the socket would have a rubber seal but nothing to engage against it). Also if you go for commando sockets then you don't get the automatic charge rate selection of the UMC - if you made a 13A plug to 32A blue commando socket, then you'd risk accidentally overloading the plug. Probably the only satisfactory answer for use in damp conditions is the Dribox - at least you can use it to store the rolled-up cable. The really proper answer would be a dedicated 13A EVSE (instead of the UMC) with an extremely long cable rather than using an extension. But nobody sells those, and probably you wouldn't buy them if they did.

Also of concern is RCD protection. The UMC provides RCD protection - but only to the cable downstream, it can't protect the extension lead. Possibly the socket you are plugging into will be RCD protected, possibly not. You can get plugs with integral RCD, but I don't like them much for this application as they potentially interfere with the cooling of the plug/socket combination that as already noted is the critical point. Something like this would probably be a better bet (not a specific product recommendation - I've not tried this particular one):

In-Line RCD Circuit Breaker rewireable IP54 13A 30mS/mA: Amazon.co.uk: DIY & Tools

Anything in particular I should think about when choosing a socket when I arrive? (assuming there is a choice!) Any way to choose circuits more likely to be more comfortable with sustained load?

Almost certainly some sockets will be better than others, but it's hard to tell by just looking.

The biggest concerns are the plug/socket combination itself: they will get warm even if everything is in good order, and the prospect of cowboy wiring.

If choosing a double socket, make sure there's nothing significant plugged into the other socket of the pair: double sockets are only rated at 20A split between them (the formal test puts 14A on one and 6A on the other), and also the wiring leading to them is permitted to be only rated for 20A. Metalclad sockets are better than plastic ones, in the unlikely event you have a choice. Sockets with signs of wear or discolouration of the plastic around the holes that shows sign of previous overheating are obviously bad news.

There's also the risk of overloading the whole circuit such that the breaker trips - not a safety risk as such but a big nuisance. Particuarly an issue at hotels where they are often pushing things harder than a typical home.

My understanding is that I'm going to get 10A / 2.3kW and around 5 MPH. Naive question I expect: why can't I get 3kW?, given that's my understanding of what a 3-bar-fire will use

You can't readily buy 3-bar fires any more. Drawing 13A from a 13A plug is marginal, and has got more so over time - the safety sleeves that appeared in the '70s in place of solid pins, and the general cheapening of all products even by "reputable" brands, that they get away with because very little these days uses that much power. Most heaters you buy now are 2500W or less, and have thermostatic controls. Also, there was always a hidden assumption that if you were leaving a 3-bar fire running continuously then the building must have been pretty damn cold and so the issue of overheating was less of a problem.

So, drawing only 10A is the compromise most EV suppliers have come to as a balance between risk of overheating and actually getting some useful charging done. Note that resistive heating is a square-law relationship, so a small reduction in current can be useful. Reducing from 13A to 10A gives you 75% of the charging rate but only 60% of the unwanted heating.


Overall, charging from 13A sockets and using extension leads is always more risky than using a proper chargepoint, but it may be an acceptable risk.

Probably the most important advice is to never simply plug in at an unfamiliar location and immediately go to bed - try to leave an hour or so for problems to develop and check for anything getting hot before turning in.

 

[WannabeOwner]

Excellent, instructive, answer; thanks @arg - I'm really glad that I asked. In particular I'll check with my host (if they know!) whether the circuit has RCD protection and I will check for excess heat a while after starting charge and before going to bed.

I'll buy the quality H07RN-F lead from my first link rather than skimp - if I find that 14M turns out not to be enough (it will also have the UMC extension too of course) I'll buy the 25M instead.

I thought the DRiBOX would be an additional bulky space-annoyance; I had seen a suggestion to use it to house the cable itself, but mentally discounted that, but now I've checked the dimensions:

Inside Dimensions Length 285mm,Width 150mm, Height 110mm

it would be big enough, and that will stop the extension getting knocked about by other junk floating (nay "flying" when on WOT!!) about.

You can get plugs with integral RCD,

I suppose those piggy-back type of RCD 13-amp plug/sockets either won't allow enough umph, or will limit heat dissipation? If that would be OK how would I know which was a quality one? Photos and Descriptions of both cheap and expensive ones look the same to me.

 

[WannabeOwner]

Just spotted that they supply a lead with RCD plug. I wonder if that would be better than getting one just with a 13AMP plug, or if there are any downsides? What if it keeps tripping? I won't get any charge ... of course the building won't burn down either!

(The original wiring we had here was mineral-cable (I think I have that right) with an outdated voltage-trip of some sort, but it was hopeless with RCDs - and yet, according to my Sparky, "if the building burnt down the wiring would still be standing" ...)

14m RCD protected single socket 13amp heavy duty extension lead

 

[cheshire cat]

take a look here lots of info

 

[arg]

Just spotted that they supply a lead with RCD plug. I wonder if that would be better than getting one just with a 13AMP plug, or if there are any downsides? What if it keeps tripping? I won't get any charge ... of course the building won't burn down either!

It's nice to have an RCD, but I fear (without having made any tests on that particular model) that an RCD plug will tend to run hotter than a standard plug. Another issue I forgot to put in the previous post is the fact that it's quite big and sometimes won't physically fit - if you find an outdoor socket with a lid for example. For that reason, I prefer the in-line RCD mentioned earlier.

If you are wanting to order from the people you linked to, they do use in-line RCDs in some of their other cables, and appear to make things to-order, so would probably be happy to make one with standard 13A plug and in-line RCD if you asked:

1m 16amp extension lead with inline 16a rated RCD

(The original wiring we had here was mineral-cable (I think I have that right) with an outdated voltage-trip of some sort, but it was hopeless with RCDs - and yet, according to my Sparky, "if the building burnt down the wiring would still be standing" ...)

Mineral insulated cable is still used, particularly in Churches and other historic buildings as it's robust yet unobtrusive, though very few electricians still have the skills to install it. It can give high leakage and so trip RCDs if damp gets into it - though this is normally only an issue with spare lengths of cable sitting on the shelf too long, once properly installed it should be waterproof.

Old installations ('60s-'70s) in rural areas often had voltage-operated earth leakage circuit breakers (VoELCB) which attempted to detect earth faults by measuring the voltage between circuit earth and 'true earth'. So they protect against wires coming loose inside metal-cased appliances, but don't offer any protection at all to people touching (say) a damaged cable. Modern RCDs are much more effective.

 

[WannabeOwner]

Thanks @arg

particularly in Churches and other historic buildings

Don't live in one of those but the word from the locals is "Five concrete lorries went to the original owner's new factory, and one came here" ... which might explain the choice of wiring (which had VoELCB as you surmised). My sparky was also of the opinion that damp was the cause. We've rewired the whole lot since ... but I was imagining that if I plugged in at a site with Mineral insulated cable and VoELCB I might well find that an inline RCD tripped, and no workaround. A piggy-back RCD, or yet-another-short-extension-cable with inline RCD would give me chocie

(but with 13AMP Plug/Socket) [Link]

Lot of faffing about though ...

... health and safety abounds, but maybe my view is acceptable: inspect cable, replace if damaged. Choose cable route carefully - park car most appropriately for charging and cable route. Try to get confirmation that the socket is both suitable (not sharing the arc-welding kit!) and protected. Check for excessive heat.

That said, what if I am not parking at a friend's house, but at a hotel where they have let me trail a lead and use a suitable socket?. Lots of Joe Public wandering around ...

I would like to carry a piggy-back RCD plug and use whenever possible (indoor socket). Then check that too does not get hot.

 

[arg]

but I was imagining that if I plugged in at a site with Mineral insulated cable and VoELCB I might well find that an inline RCD tripped, and no workaround.

It shouldn't. The leakage should only be seen upstream of the point where it's occurring (hence the fact that we need this in the first place - because the UMC's RCD (downstream) can't see the hypothetical fault in the cable).

So if your in-line RCD is tripping there's probably a genuine problem.

A piggy-back RCD, or yet-another-short-extension-cable with inline RCD would give me chocie

Though if you are really going to town on this, making the main cable with a 16A commando plug and then having a short tail 13A plug -> inline RCD -> 16A commando socket might not be a bad idea, giving you the option to plug in to caravan supply points (which have 16A commando outlets and are expected to have integral RCD).

 

[WannabeOwner]

he leakage should only be seen upstream of the point where it's occurring

<SlapsForehead> Of course!

The issue,for us, and probably what lead me astray, was:

Move meter to allow knock-down & rebuild of garage
Take opportunity to do away with original VoELCB board and fit a nice modern distribution board in the new location
Then discover that a good proportion of the circuits trip the RCD

Followed by "decide to rewire the whole house"

 

[WannabeOwner]

Stumbled over this B&Q item for £20

as mentioned in a thread at SpeakEV and also this for £8 - no RCD though

 

[NullException]

I bought this, because it's generally useful around the house. Fully unwound, it's rated for 3kW. I haven't used it for charging yet, but expect to in a couple of weeks.

 

[cheshire cat]

I think a cheeap infrared thermometer would be a good investment too at least for the first few times

 

[cheshire cat]

(The original wiring we had here was mineral-cable (I think I have that right) with an outdated voltage-trip of some sort, but it was hopeless with RCDs - and yet, according to my Sparky, "if the building burnt down the wiring would still be standing" ...)

so that's why it's called pyro !!!

 

[WannabeOwner]

I think a cheeap infrared thermometer would be a good investment too at least for the first few times

Good idea, thanks. I've got one of those - rarely used - I'll put it in the car.

 

[S777]

Stumbled over this B&Q item for £20
UOTE]

Hi,

I realise this thread is a little old but does anyone have any experience of current options in this area? I'm just about to order a 75D MS and concern has been raised about a planned trip to visit friends who don't have a charger and are quite a distance from any superchargers. So I want to get an idea of what I'll need to pick up to allow for slow charging from a 13A socket when the car is parked a few metres from their home.

The items listed above from B&Q are still available it seems, but I'm not sure if anyone has actually used them for charging....

 

[DJP31]

This chap is a Tesla owner and very highly though of when it comes to leccy and associated bits and pieces

Xavelec - Charging cables and adaptors for your Tesla EV UMC

 

[WannabeOwner]

The first time I did this I used my friends lawn mower extension reel, and we stuffed the socket / UMC_Cable "junction" under the car so it didn't get wet ...

Pleased to say I've moved on from there!

The first issue (which I hadn't considered when deciding "I want to buy a decent extension lead") is whether the power supply, and the socket you are plugging into, at your Friend's house is up to the job

the second thing is how long / fat a cable do you need.

For the first point: the discussion (as I remember it) revolved around having some sort of trip so that if your extension lead develops a fault and IF you friend's wiring is not going to detect it, then YOUR cable fails safe. (Your friend's system may, separately, fail safe, including for other reasons - e.g. you are drawing too much power, but it might not).

So you could have a 13-AMP plug incorporating a "trip", but those combined-plugs tend to be bulky and may hinder your ability to plug into a 13 AMP socket (e.g. where space is tight).

In terms of the actual cable I would recommend considering one-size-up from the length that you are buying. The longer the cable the fatter it needs to be (but for this job even relatively long cables are still comfortably skinny). In addition your will be plugging your car's UMC cable into the extension lead, and that that itself has several meters of length, so that may well push your extension cable over its designed diameter-for-length. The result will be that either something trips (annoying, and you are then stuck because you cannot charge ... it will trip every time) or it may heat up; that may not matter (if its "not much"), but its best avoided, and heat also means less efficiency so at best you will be wasting some energy, and at worst you will be gaining fewer miles-of-charge, such that you don't have enough by the time you want to leave.

The previous decision also covered having some flexibility to plug into different types of power source. What do you want to be able to plug into? Assuming primarily 13 AMP socket, what about on the continent? or "outdoor" connectors, such as "Commando" (common at camp sites, and carrying more power than a regular 13 AMP socket). Do you need 3-Phase capability? If so then you could consider a short "adaptor", which can easily include a Trip, if you want, and then a longer extension lead (most probably with a Commando-connector rather than 13 AMP plug). So you plug your 13-AMP-to-Commando (short adaptor, optionally including protection-trip) into Friend's 13 AMP socket, then commando-commando (long extension lead) and then Commando-to-car (using the Tesla UMC cable).

The simplest is a 13 AMP extension lead, long enough, and "fat enough" to allow for combination of Extension lead PLUS Tesla UMC lead. That's what I went for (but I did actively consider the other options). It also works great for my (commercial-sized) pressure washer which trips every other ["Domestic"] extension lead that I have in the house

Only other consideration [that I can think of ...] is how you keep the rain off the connection between your extension-lead and the Tesla UMC cable - which may well be in the middle of your friend's lawn / driveway ...

You can get a "dry box", but they are not exactly cheap, or rig something up with a plastic bag

I have adopted some good advice that @arg gave me which was to feel the plug (into your friend's 13 AMP socket), after 30 - 60 minutes charging to check it has not got hot, and to check that again before going to bed.

I got mine from Industrial Extension Leads. It uses "H07RN-F tough rubber cable" which won't give up at the first sign of bad weather, nor sitting in the sun. I don't think they sell a fatter-but-shorter lead (to compensate for the additional length of UMC cable), but they do do bespoke - or make sure that the length you order, plus UMC length, would not incur a fatter cable if bought as a single extension lead.

 

[S777]

Thank you both very much, that is fantastically helpful information and the website you linked provided a solution I hadn't even considered with the letterbox connector so it's possible to run a cable without leaving a window wide open all night!

I have quite a bit of reading to do now....

 

[DJP31]

Thank you both very much, that is fantastically helpful information and the website you linked provided a solution I hadn't even considered with the letterbox connector so it's possible to run a cable without leaving a window wide open all night!

I have quite a bit of reading to do now....

No problem. You’re doing exactly the right thing by considering this sort of thing ahead of ordering. I looked at all the routes I was likely to take, what the real world range was etc etc. The last thing I wanted on spending miles more than I ever have before on a car was a big dose of buyers remorse. For clarity, I don’t have any buyers remorse, it’s an outstanding car.

 

[WannabeOwner]

The last thing I wanted on spending miles more than I ever have before on a car was a big dose of buyers remorse

Good point.

Glad I bought the bigger battery. Spent ages agonising over the significant capital cost (and at that time didn't know about faster supercharging and shorter supercharging time because "fewer get-you-home miles" required). I just thought that £X,000 for N additional miles of range was a lot per mile

Glad I bought a CHAdeMO adaptor. Even though I've only used it twice.

Glad I bought a decent extension lead. I've not used that much either (except for Pressure Washer!)

Glad I got that cost out of the way at the outset and, since then, I've had the benefit ... and forgotten about the initial cost.