Nema 6-15 to nema 5-15 (hot hot ground)

Question

Let me preface this by saying i did my research, i got an electric car and the charger is limited to 12A draw internally, but it is designed to handle both nema 6-15 and nema 5-15 specs. If you run it at 110 12A it will charge in 9 hours, if you run it at 220 12a it will charge in 4.5.

The adapter already came with a nema 5-15 which i cannot change as it has a temperature sensor in it which i would like to keep, but if i send hot hot neutral through its nema 5-15 connector it would treat it as 6-15 and operate correctly.

I already have a 2phase panel outdoor for my hot tub rated for 50A where the hot tub has a 30A breaker. I will be adding a 2nd 20 amp breaker for this.

The question is as follows, should i run it into a nema 6-15 plug, then build a converter from 6-15 to 5-15, or simply use a 5-15 and wire it hot hot ground. I would be violating code, but adding in an adapter is pointless, the wiring is meant to handle 12 amps regardless of voltage, so i assume a 5-15 should handle 220v 12a without issues.

What are your thoughts?

Answer 1

Installed fixtures must be correct

Any receptacle which is installed as part of the building must be exactly what it says on the tin. If you are provisioning 240V hot hot ground to the receptacle, and breakering it for 15A, it must be a NEMA 6-15. Period.

The simple fact is, if you provision 240V to a NEMA 5, it will be a matter of time before someone plugs a 120V appliance into it. You know the feeling, you're trying to get something done, you have a 5-15 plug in your hands and you search for the nearest receptacle your cord will reach. Everyone else does the same thing. And that's the problem. Your rush to an immediate goal is no excuse. A reasonable person will foresee that a miswired NEMA 5 will find a victim, just a matter of time. An exacerbating factor is that you're intentionally refusing to pull a permit and get inspected because you know you'll flunk.

Just don't do it. Seriously. Not meaning to be a nag here, just there's a better way to do that thing.

The cheater is the way to go

None of this is legal. But since it's not part of the building, the AHJ (building inspector) doesn't have nearly as much to say about it.

A 6" long homemade extension cord will send signals that makes it far less likely for an innocent person to have an accident. First, there's no logical reason for a 6" extension cord to exist. Second, it's obvious that the plug is weird, presuming that you use a NEMA L6-15 locking type. Also, label it clearly, and attach it securely to the charger with a cord coupler.

Answer 2

No matter what you do with what ever hacked adapter cables you try to kludge up DO NOT WIRE UP AN OUTLET INCORRECTLY. If you wired an outlet that is normally a service connection for 110-120VAC and made it source 220-240VAC you are just asking for long range trouble and risk.

Best case would be you would be the only one to use it and hopefully not forget and plug in something that blows up in your face making it so you could never drive said electrical vehicle again. Just think of the liability you would have on your shoulders if someone else came along and used this kludged outlet and was killed or maimed. It could be one of your kids for all you know.

Answer 3

The charger may need to be modified internally to adjust to the higher input voltage. It's not uncommon to use a voltage doubler circuit followed by a switch-mode power supply in a 120 V appliance that needs high current DC like a battery charger.

This internal wiring looks almost the same in 240V input mode and 120V input mode

The voltage double circuit is a bridge rectifier followed by 2 capacitors in series across the DC output. In the doubler configuration the center tap of the capacitors is bridged to the neutral of the 120V AC input. This then provides 360V DC to the switch-mode power supply. To change this over to 240V input you need to cut the link between the neutral an the center tap of the capacitors.

If you don't then you will be feeding 700V DC to components that are only rated to 400V.

Answer 4

Of course it's a violation of the electrical code to wire up a 120V outlet to 240V, and if there is a fire incident or appliance injury anyone or any insurance agent who finds out about this will try to blame it on this even if it didn't cause the incident. If you are legally subject to the electrical code, then it is also a violation of the law.

But being LEGAL is often not the same as being SAFE.

It's actually very unlikely that plugging a 120VAC device in to a 240VAC outlet would cause personal injury. Most things will either blow fuses or smoke and burn out. This is what happens anyway when these devices fail due to wearing out or due to defects. The biggest risk is probably some someone plugging in some kind of transformer or motor that will appear to work fine but will take several minutes to over heat and potentially catch fire (which it would also do at 120VAC if it had a shorted winding). For that to even happen it would have to lack proper thermal fusing or be some non UL listed imported device. Surge protectors, especially ones from the 90s, can also catch fire. They're a hazard waiting to happen even at 120VAC. The line to earth shock hazard at 240VAC is still 120VAC due to the split phase wiring system.

Due to the typical duty cycle of welders, the NEC allows dedicated outlets for welders (which are standard and don't prevent other appliances from plugging in) to be fused at twice the normal current carrying capacity of the wiring. Normally this would cause a lot of harsh opposition on a forum like this, much like using 5-15 in place of 6-15, but because the NEC allows it, there is little to no opposition.

I checked out a situation where the neutral line feeding a rental house had snapped. The 120V circuits were surging high enough to partially melt the plastic and let black smoke out of a surge protector. That could have caused a fire. Do you spend several hundred dollars on buying an official 240VAC EV charger, or do you spend it getting rid of dangerous surge protectors and improving the ground rod for the building? Doing one of those things will make you NEC compliant, and the other will actually make you safer.

I once shared my intention to put a thermostat on a car engine to kill the ignition if it overheated, to save the engine. Some people thought this was a terrible dangerous idea. In the real world, the danger of an engine stalling in a properly driven vehicle is very small. What can happen is that the car will be destroyed, the owner will instead ride their motorcycle to work where they will be over 10 times a as likely to die in an accident per mile traveled.

The conclusion is that safety is in your own hands. You can choose to be legal and code compliant, but being safe costs money too, and it often gives you less safety to spend money on struct code compliance than other often forgotten safety issues.