New electrical code could doom most common EV charging

edit: 120V is not immune. I once worked on a project involving powering equipment in a Faraday case at 120V. The mandatory filter (to prevent the wire from conducting emissions out of the cage) instantly tripped GFCI.

The right solution IMO would have been one of:

a) A better filter that doesn’t pass 50-60Hz. This is doable in theory, but I’ve never seen one.

b) A transformer or other isolated supply outside the cage, with a GFCI inside the cage (to protect the people who may enter to touch the equipment).

c) A transformer outside, not necessarily right next to the cage, supplying the inside with two opposite-phase lines at 60Vrms each. No net leakage! This would require that everything inside accept such a supply, which rules out anything that wants a real neutral.

d) I bet someone could design a transformer with a shield between the windings that would integrate with the Faraday cage. Power would couple in inductively through the shield. Common-mode RFI would have a very hard time escaping, and different mode RFI could be filtered and probably matters quite a bit less anyway.

Of course, the actual solution chosen by the site’s electrical people was rather less classy.

Something like this?

“Though you rarely will see your bathroom GFCI trip (unless you’re dropping the hair dryer into the bath water), some kinds of larger, more complicated machinery can cause nuisance trips.”

But I've never seen an EV charger trip an RCD!

It's actually kinda easy - the way GFCIs work is pretty neat.

You pass the live and neutral through the same magnetic field sensor. So long as none of the current is escaping to earth, you get an equal current in each direction and the total magnetic field is zero.

The problem is you can get a 5mA leak to ground because of, say, condensation inside a socket. And ripping out your house's wiring in search of that is a lot of expense to deal with a relatively minor danger.

The reason why is that those devices create arcs, and AFCI breakers are completely unable to handle them. Some regions require AFCI breakers, so a significant portion of household appliances will occasionally trip the breaker.

The worst part is that it isn't particularly consistent, so your fridge could last for years without tripping it, but as brushes wear the arcs they regularly create increase the chances of a trip, until one day you find that all your food is ruined, because the AFCI breaker tripped at an inopportune time.

Fortunately, my fridge trips the AFCI very reliably, so I was able to detect it before losing any food. All I had to do to fix it was make a few passes with the hot wire through a ferrite bead, right before it connects to the AFCI breaker. It completely blocks the arc-created RF that the AFCI is detecting, disabling the functionality of the AFCI, all without any code violations, because while the AFCI is required, the ferrite bead isn't prohibited.

It turns out that detecting arcs is hard. Really, really hard. The window between "normal operation of some random crap that's plugged in" and "bad stuff" is tiny, or even nonexistent. (Old tools with brushed motors arc during normal operation!) I worked on an arc fault detector once, as part of a larger project. We never got the thing working before the whole project got canned. It was consistently the one piece of the project that I was reporting to management as "We have no idea how to make this work. The rest of this thing, we have a plan for (maybe a bad plan, and maybe we won't execute well; such is life in R&D), but the arc detector doesn't work, we have no plan for it, and no idea how to make a plan." And we were doing a next-generation version of a device already shipping — we should have had a working arc detector right out of the gate! But it didn't work.

(The tests for arcs, incidentally, were insane. We used the test procedure from the previous-generation product, a special board made up with various "simulated arc strengths". Then we set up a low-kV range power supply, put on those giant rubber gloves that you see in cartoons, and moved in a pointy probe, by hand, toward the right spot on the test board until it arced over. This was less than reliable, and rather difficult to automate. (My proposal to automate testing by changing the intern's name to "Automated" was not accepted.) It turns out that the arc signature is deeply dependent on the exact test method you use. We had another fixture designed in-house involving a variable-distance spark gap made with two adjustable spheres. Its results were completely and totally different than the other board, so we just pretended it had never existed.)

So arc detection is difficult. It will not surprise you then to learn that the first generation of AFCI devices and breakers did not actually work correctly. They were notorious for tripping randomly and generally not things you wanted to have in your life. They were also expensive (probably paying more for the testing than for the materials cost). The NEC mandated their use anyway. Their reliability was so ridiculously poor that there was general agreement among everyone that that part of the NEC should just be ignored and standard or GFCI devices used instead. Did the NEC care? No, they insisted that AFCIs were important. Even though they didn't work. This made a lot of people start to distrust them.

We're on second or third generation AFCI devices now, and they seem to have improved a lot. They don't really false trigger anymore. But do they correctly trigger, or did they just desensitize them so they don't do anything at all? I haven't tested, and I don't want to!

It's also worth considering the risks mitigated by AFCIs. Arc faults at 120V are not really that common, and when serious arc faults do occur, they usually result in an electrical fire. Fire is certainly very bad, but I'd say it's a lot less dangerous than the nearly-instant death by electrocution that GFCIs prevent. (Note that at 240V arc faults are much more common, and up at 480V they are straight-up lethal in their own right. DO NOT FUCK WITH 480.)

So the NEC mandated AFCI devices that caused major hassle, mitigated minor risks, and cost a lot of money. That annoyed people. This came on the heels of them requiring GFCIs everywhere (same issue; ground faults in non-wet locations are not really a major risk with North American style TN-C-S earthing, but at least GFCIs work). That annoyed people. And then they had required TR receptacles everywhere (which, personally, I consider of very little benefit, though I won't argue with anyone who disagrees; at least it's obvious what's going on there), when that technology was also half baked (seriously, early TR receptacles were horrid to use, though they are pretty decent now). That annoyed people.

You can see the trend. A lot of crappy technologies were made mandatory at our expense for minor to modest gains in safety, high losses in reliability, and extreme costs in annoyance. Thus, the question: who are these guys really looking out for? Us? Manufacturers? Insurers?

I think the NEC is beholden to the people who make this stuff. Right now I have a 14-50R in my garage (I don't even use it, I have it shut off at the panel; I don't have an EV, this is just new construction). The standard breaker is $18.98 right now at the big orange store. The GFCI version they're trying to make mandatory is $190.68.

I think that says all you need to know.

(And before anyone says they must cost that much more to make... they do not. I have designed GFI and AFI devices. You need to add a circuit board, yes, a pretty rugged one. The ordinary breaker is all mechanical. But that does not cost $170 more to do.)

Notwithstanding that electricity for any use already has a per KWh tax added. Plus sales tax of course.

Or let's phrase it like that: If the proper cables are used and if the wiring isn't absolute dogshit next to other absolute dogshit the cited reason isn't the reason.

Try to induce 5mA of foreign circuit into a cable on purpose and you will see what I mean. Measuring equipment exists so we don't need to guess here..

The issue is more that manufactureres calculated with a 30mA threshold for ages and if they did a bad job, they produced equipment that just barely made that threshold. Typically such norm changes are known well ahead, I am more familar with European norms, but changes like these are known a decade ahead.

So it isn't as if manufacturers of such equipment are suddenly surprised by new regulations. And if the new rule starts to work that should only affect newly built unints (or units where the electrical installation is renewed). So if your EV charger trips the GFCI because of bad electrical wiring, thr wiring likely had to be replaced due to new norms anyways..

Why the thresholds for different areas differ is usually a mix of historical reasons, lobbying and a "we didn't get around to that yet". It is hard to answer such questions in isolation, maybe marine equipment has other maintenance cycles, crazier cabling requirements, maybe there are fire suppression measures that allow to relax that requirement more, maybe it doesn't make sense at all.

As someone who has read through nearly 100 GB of norm PDFs I can assure you that just comparing two thresholds in isolation is practically worthless if you ignore the other differences in the rules.

Look out your window at the power pole, you'll see a transformer. That has breakers, differential relays, and other protections.

> And that protection?

Substations have RTUs and SCADA systems that are constantly monitoring everything for faults. They have cool shit like oil breakers that can kill even the large inputs to the substation.

> At some point you have to stop.

No, you don't. The protections go all the way back to the power generation site.