Pro Charging Station to NEMA 14-50

[Maquis]

Dumb question. Could this plug into my dryer outlet in the garage,

Yes - you would have to use the correct cord/plug and set the physical current limit to 24A.

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[Nick Gerteis]

Dumb question. Could this plug into my dryer outlet in the garage,

Considering your low daily mileage, dryer outlet would be perfect. And free, since it’s already there!

 

[jefro]

Some of the evse makers frown on the older dryer plugs and don't provide a model to fit them.

I'm kind of confused too. Your 14-50 outlet should have been fully 50A capable. Yes, a 30A circuit needs an EVSE set to 24A.

I could drive a F150 100 miles a day I assume and charge it at 240VAC 24A overnight. My charger only runs 4 hours a night so once in a while a weekend tops off the battery.

 

[hturnerfamily]

-an 'old' dryer outlet was typically only a 3 wire, with no Neutral
-the Nema 14-50 is simply the 'new' dryer outlet, with 4 wires, including the Neutral

some EVSE come with Nema 14-50 right out of the box, some come with a 240v 20amp male plug, like mine, others come with a simple household regular 3-pronged male plug(120v), etc., there is no current 'standard' - every home and ev owner has a different situation. There is no 'best' plug/outlet if the outlet can handle the power needs of the EVSE.

and, there are PLENTY of various adapter for almost ALL situations, whether the manufacturer of the EVSE likes it, or not....

 

[jefro]

Amazon makes a gizmo to sort of fix that lost ground line but not sure I fully like it. Better than nothing. A green wire goes to a 120V outlet three prong.

One might be tempted to use a 50A device on a 14-50 but with that 30A breaker and I assume wire isn't able to use it. I know my dryer is the new plug but I had to change the neutral prong to angle.

 

[hturnerfamily]

there can be confusion about how electricity and outlets work, and their capacity, but the main issue is always whether the WIRE can handle the amperage, or the HEAT, that runs thru it to power a device. And, it's not the wire itself that's any issue, it's the wire's outer protective COATING - meaning that the wire is designed to be able to handle a certain maximum amperage, for a certain length of time, before the HEAT could cause the protective outer COATING, usually a rubber or plastic sheathing, to possible BURN thru, creating a hazard for anything it touches. Usually this is a problem when wiring is installed and hidden within WALLS.

Now, the wire itself doesnt' care about the device that's plugged into the outlet. The wire is only there to transfer electrical current, but the thickness/size of wire allows the wire to dissapate heat effectively. A small thickness wire, like 12awg, might be the size that is connected to most of your regular household outlets, since it is connected and protected back at the main panel with an appropriately sized 15amp Breaker.
If, though, you have that same outlet, with that same wire, only protected with a 30amp breaker, it's possible that the wire could overheat, due to a large-draw device asking for more power than the wire is sized for, and the larger breaker would not then 'protect' that wire, until it's too late. The breaker never tripped because the wire actually burned BEFORE the amperage exceeded 30amps.

WIRE size is the most important factor in safe wiring, and the breaker SIZE is the next most important. Whether the outlet or device uses 3-wires or 4-wires is more of a safety measure for Humans who might TOUCH the outlet or device that has a grounding or neutral issue at that moment.
If you have a 3-wire device and use an adapter to plug it into a 4-wire outlet, you have no issues, since the device does not use a Neutral wire, anyway. There is no difference. Many or most EVSE devices are 3 wires only - they don't use a Neutral, nor do they need one. If you plug that EVSE into a 20amp 240v 3-wire outlet, like mine does, it works perfectly. If you use an adapter and plug it into a 4-wire NEMA 14-50 outlet, you are just as successful, and it works exactly the same.
I would bet that the Ford mobile charger that comes with the truck, that has the Nema 14-50 plug adapter, only uses 3 wires, too. It has the Nema 14-50 4-prong male plug mostly because a Nema 14-50 outlet is more of a 'standard' for up to 50amps of power than any other outlet. It has become a standard now for Stove/Ovens, DRYERS, and even RVs/Motorhomes. It's a much more useful outlet than any other smaller 240v outlet you could find.

As for whether you 'cannot' use 50amp of power from a NEMA 14-50 outlet, that is debunked - FOR SURE you can - that's exactly what it's designed and WIRED for. This outlet uses a 6/4 Wire - which is designed for up to 55amps of continuous power, so, no issues there. There will always be some minor exceptions to the general rule, such as how long the wiring is from the main panel, but those don't change the basic pretense of the capacity of the wire. Also, if a device says that it can use a NEMA 14-50 outlet, then it is already DESIGNED to use that capacity, or LESS than that capacity. Generally, any device designed to plug into that outlet will actually be drawing LESS than the maximum 50amps of 240v power.

As a motorhome owners for many years, with a 50amp 240v electrical system, we found that using a NEMA 14-50 outlet at many campgrounds was exactly what the motorhome was designed to plug into, although it is a much different underlying electrical equation. A motorhome is not an EVSE, meaning that the motorhome is not always using the exact same amount of power draw, from each 'side' of the 240v power, as and EVSE does, or, like your oven or dryer does. A motorhome may have a front a/c unit running, while the microwave is cooking, while the tv and satellite receiver is on in the back. All of this means that there is no 'perfect' balance between both 'sides' of the 240v power at any given time. The NEUTRAL is part of the NEMA 14-50 plug/outlet for that very reason - the 'sides' need to have balance, and the neutral wire provides that. This is one of the few situations where the neutral wire on a 14-50 outlet is used.

 

[beatle]

As for whether you 'cannot' use 50amp of power from a NEMA 14-50 outlet, that is debunked - FOR SURE you can - that's exactly what it's designed and WIRED for.

Except for continuous loads like EV charging. Then the code says you need to derate the circuit by 20%. So max safe amps is 40A on a 14-50, 24A on a 14-30, 16A on a 6-20, etc.

 

[hturnerfamily]

that's pure balony - the breaker is designed to protect the circuit wiring, regardless of whether one might consider 'continuous' loads, or not, whatever that even means. The 'code' is referring to other devices/appliance or draws that might be on the same circuit - these EVSE are on dedicated circuits. I've used NEMA 14-50 outlets for many years, especially in the RVing world. The breaker trips when it senses too much heat, like it's supposed to. It has no reason to trip, otherwise. The 6/4awg wiring can easily carry even more than 50amp, whether continuous or not.
But, go overboard and do what you will, I've never had any issues with it, and won't in the future, either. If a breaker is not designed for a continuous load, it won't say so.

 

[hturnerfamily]

and I don't mean to discount what people might read in the 'code', but my experience over many years does not negate what the breaker size SAYS on the breaker, itself. If it's a 50amp breaker, it's designed to handle 50amps of power, that's why it says so. If the code did not allow it to, it would not be allowed to be printed on it. Have fun! It's not really that complicated.

 

[beatle]

That's not my rule or recommendation, it's the NEC. 6/4 is rated for 55-75A depending on the temperature.

https://afdc.energy.gov/files/pdfs/EV_charging_template.pdf

Overcurrent Protection Overcurrent protection for feeders and branch circuits supplying electric vehicle supply equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the electric vehicle supply equipment. Where noncontinuous loads are supplied from the same feeder or branch circuit, the overcurrent device shall have a rating of not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads.​

​

That means you must multiply the continuous load by 1.25, and that is how you calculate the breaker size. Even if adhering to the circuit derating code, I'd also recommend getting a high quality 14-50 receptacle. I bought a standard $10 Leviton 14-50R at Home Depot back in October 2019 along with 6/4 Romex and a 50A breaker. I happily charged my car at 40A (over 10,000kwh) since then until I found this last week:

The breaker did not trip, and my old Tesla connector does not have a temperature sensor in the plug. The heat was concentrated in the receptacle. Eventually the resistance was so high that the car noticed poor power and refused to charge which prompted me to investigate. The breaker would have only tripped had there been a short, and by that time my entire wall would have been on fire.

After doing some research, apparently the Leviton is known garbage. Some people have had failures with it after only a few months - perhaps accelerated by frequent plugging/unplugging of the connector. I left mine plugged in semi-permanently so maybe that's why I was able to get over 2 years of service out of it. Popular brands are Bryant and Hubbell. The Utilitech from Lowes is also a good budget option which is what I bought. Eventually I'll just use the hard-wired EVSE from Ford when I get my truck and decommission this receptacle.

Do what you want, but don't recommend people to be so cavalier in disregarding code requirements.

 

[adoublee]

that's pure balony - the breaker is designed to protect the circuit wiring, regardless of whether one might consider 'continuous' loads, or not, whatever that even means. The 'code' is referring to other devices/appliance or draws that might be on the same circuit - these EVSE are on dedicated circuits. I've used NEMA 14-50 outlets for many years, especially in the RVing world. The breaker trips when it senses too much heat, like it's supposed to. It has no reason to trip, otherwise. The 6/4awg wiring can easily carry even more than 50amp, whether continuous or not.
But, go overboard and do what you will, I've never had any issues with it, and won't in the future, either. If a breaker is not designed for a continuous load, it won't say so.

It's not pure balony when considering safe long term operation of a circuit. Breaker will carry it continuously but it is not allowed by NEC unless breaker is explicitly 100% rated (the UL listing describes the 80% rating of standard breakers, no need to print it where you see it if you just follow the NEC rules). NEC concern is heating.

IS_37_80-versus-100-rated-ATS.pdf (cliffordpower.com)
Molded Case Circuit Breakers (ul.com)

 

[RickLightning]

One of the downsides of EV adoption is going to be housefires. Why? Because of many reasons, some of which are identified in this thread. People are going to plug into dryer outlets not designed for the load, and wires are going to overheat, and houses are going to burn. That's just reality.

I strongly recommend to anyone that asks me about installing an EV charger, or outlet for a charger, that they both hire an electrician AND insist on an inspection.

 

[FlasherZ]

Hi folks - years ago I wrote the home wiring FAQ for the Tesla forums, and many of the same questions and observations were made there too. Two major questions... 1) is it safe? and 2) will your insurance deny or tie up your claim if they do a post-loss inspection after a loss?

Failure to follow code is a reason to deny your insurance claim in some jurisdictions, especially if it is a cause to an event that causes loss. I did a lot of work to research this, because on the Tesla forums we had people who swore up and down that 6/4 Romex was legal for a 48A charging install (it's not). #6 in conduit is legal, but 6/4 Romex is not. (48A requires 60A ampacity due to continuous current, and Romex must use the 60 degC chart, which is only 55A.) Why not spend the money to do it right, so you don't lose your entire home's value if it does burn down?

The difference between continuous current and intermittent current is a critical distinction, and whether Leviton or any other manufacturer, the testing standards for both are different. The NEC has the continuous current aspect in there for a very important reason. Infrastructure gear is marked based on "typical" usage patterns, and most loads at those amperages are intermittent. Very few appliances draw continuous loads. That's why the 125% rule exists in the code -- and don't expect to find gear rated for 100% continuous in home use, it's just not common.

The reality is there is a major difference in whether something will work, or whether it's safe. In many years of doing electrical work, I've seen enough melted breakers, receptacles, etc., that were used in "normal" applications, much less continuous. Tesla had to build in special algorithms to detect high-resistance issues due to loose lugs, extension cords, etc. - and if it detects that there is a higher-than-expected resistance due to that, it will cut charging rates by 25% (or more).

Finally, the use of a power cord on EVSE is subject to several special rules in section 625. It must be very short (12 inches maximum, NEC 2014 625.17(A)(3)(a)) at the higher current because of ground fault and potential damage requirements. If the prongs get dirty, you end up with a high-resistance situation (see the melted plug, above). I've replaced 4 different Tesla wall connector cords because over time the pins wear and aren't as effective - so heat from dirt is a real thing.

Tesla had problems with its first-gen charging cords because the modular connector pins would get hot and melt. As a result, Tesla mobile connectors only work at 32A charging now (and there's a good market for the older ones that do charge at 40A).

Be safe out there.

 

[FlasherZ]

The 6/4awg wiring can easily carry even more than 50amp, whether continuous or not.
But, go overboard and do what you will, I've never had any issues with it, and won't in the future, either. If a breaker is not designed for a continuous load, it won't say so.

You're generally right. But what will your insurance company say post-fire if they discover that you weren't to code? I don't want to take that chance.

It is true that 6/4 can carry more than 50A. It'll carry a few hundred amps while it warms the room quite nicely. #6 wire fusing current is just over 650A. I've seen enough burned panels, receptacles, equipment, etc., to know that continuous current requires well-maintained infrastructure.

I make the recommendation that people follow the code to 1) be safe, and 2) protect their investments. I have talked to several people whose post-fire insurance investigations turned up items that weren't kosher, and as a result they had to fight or even settle for less than their loss.

 

[VTbuckeye]

You're generally right. But what will your insurance company say post-fire if they discover that you weren't to code? I don't want to take that chance.

It is true that 6/4 can carry more than 50A. It'll carry a few hundred amps while it warms the room quite nicely. #6 wire fusing current is just over 650A. I've seen enough burned panels, receptacles, equipment, etc., to know that continuous current requires well-maintained infrastructure.

I make the recommendation that people follow the code to 1) be safe, and 2) protect their investments. I have talked to several people whose post-fire insurance investigations turned up items that weren't kosher, and as a result they had to fight or even settle for less than their loss.

What about things that were to code in 1960 when a house was built, but certainly not there currently?

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