Old 240V + 20Amps receptacle need to be replaced by a Nema 14-50

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tk3000

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In my garage there was 240V L6-20R, 20Amps Locking Receptacle. The 1-gang electrical box is not anchored to any stud, and the wall is all covered with pegboard panels (there seems to be some black panels behind the pegboard panels). The 1-gang box looks different, maybe a type that does not need a stud.

The thing is that I want to install a nema 14-50 receptacle there flushed with the wall. The wires coming from above seemed to be 20amps cable (yellow jack) with two hots (white wire used as the second out of phase hot/line) and a ground, the circuit breaker is a 240V rated at 20amps. I don’t intend to go the attic any time soon, so the idea is to use the existing cable, install a nema 14-50 and charge the EV at 240V and 20amps (much better than a regular outlet, for the time being). In the future, I would upgrade the wire and breaker.

The previous 240V & 20Amps receptacle:

NEMA_GARAGE_THREE_PRONG_220V_RECEPTACLE.jpg


And the new Nema 14-50 being tested (the connector/slot for the neutral is not being used, not needed for the ev “charger”):

FORT_WAYNE_GARAGE_240V_20AMP_RECEPTACLE.jpg

So, I am looking for a sturdy old-work 2-gang elect. box that would not require to be supported by a stud. Maybe something like the following (but with more volume, the larger I found has 26 cu in):
https://www.amazon.com/dp/B0CWS6XV7...=d2lkZ2V0TmFtZT1zcF9kZXRhaWxfdGhlbWF0aWM&th=1

Also, that nema 14-50 seemed to have been designed for much thicker (lower gauge) wires and instead of clamps, it uses a screw in a hole; not great for a much thinner wire.

For now, the idea is to use an oscillating multifuntional tool to increase the opening for a 2-gang elect box. Hoping that the box would fit the pegboard combined with other board behind it.

If the old-work 2-gang elect box could have more interior volume (over 30 cu in) capacity and also depth adjustment, it would be perfect as far as it fits the wall board, etc.

Thanks or any insight!
 
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You've got a couple of glitches to contend with:
A) You don't have a neutral. NEMA 14-50R requires one. Does you charger need a neutral?
B) It won't be to code to install a NEMA 14-50R on a 20 amp circuit even if you leave it protected at 20.

You might have to do some attic climbing and install a new circuit. (There are adapter plugs, but they are backwards from what you want, having 14-50P x 6-26C. The other way is dangerous.)

You asked about the box & how it was mounted.
The box is commonly called a "Gem" box. The real term is "Gangable Old Work Box Steel". The ears at the top and bottom keep it from falling into the hole.

What keeps it from pulling out are called "Madison Supports". The real term is "Old Work Box Support". Those are the folded over tabs that you see in the photo. If you re-wire and need to take the box out, bend the folded tabs back straight & the box will slide out. You'll most likely lose the Madisons in the wall, so pick up some new ones.

Also note that a 14-50R & the appropriate conductors won't meet the Box Fill Requirements in the existing Gem Box. (Probably won't fit, either.) You can gang Gem boxes for more cubic inches but the 14-50R won't be centered. Your best plan would be a 4" square deep and a mud ring or a surface 14-50R.

Paul
 

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It is against code to install a 50 amp receptacle on a 20 amp circuit. You should look for the proper adapter for the car to plug into a 20 amp receptacle.
 
Yeah, that it may be against code to install a nema 14-50 in a 20amps circuit. It makes a lot of sense for it to be against code. Code is about broad generations. It assumes that if the 50amps recpetacle is there that people will assume (understandingly) that they can hook up appliances or a charger or whatever that will draw high amperage, then the breaker will flip – it simply would be an insufferable situation. But, my situation is very specific; I am using a charger that is pre-programmed to only draw 16amps at 240V, and I am the only person who uses it. Assuming that the wires are properly connected, it is actually safer to use an outlet that is rated at 50amps in a 20amps circuit, it has thicker and more robust contacts – thus offering less resistance.


For instance, a very short 14 gauge cable is safer at carrying 20amps than a much longer 12 gauge cable carrying the same current. Code does not expect people to make complicated calculations before they do some wire installation.

Again, that situation is TEMPORARY. Once, I have opportunity to go to the attic (kind of messy and full loose insulation), a 8 gauge wire will be put in place and a 40 or 50amps circuit breaker will replace the current 20amps breaker.
It is against code to install a 50 amp receptacle on a 20 amp circuit. You should look for the proper adapter for the car to plug into a 20 amp receptacle.
 
You've got a couple of glitches to contend with:
A) You don't have a neutral. NEMA 14-50R requires one. Does you charger need a neutral?
B) It won't be to code to install a NEMA 14-50R on a 20 amp circuit even if you leave it protected at 20.

You might have to do some attic climbing and install a new circuit. (There are adapter plugs, but they are backwards from what you want, having 14-50P x 6-26C. The other way is dangerous.)

You asked about the box & how it was mounted.
The box is commonly called a "Gem" box. The real term is "Gangable Old Work Box Steel". The ears at the top and bottom keep it from falling into the hole.

What keeps it from pulling out are called "Madison Supports". The real term is "Old Work Box Support". Those are the folded over tabs that you see in the photo. If you re-wire and need to take the box out, bend the folded tabs back straight & the box will slide out. You'll most likely lose the Madisons in the wall, so pick up some new ones.

Also note that a 14-50R & the appropriate conductors won't meet the Box Fill Requirements in the existing Gem Box. (Probably won't fit, either.) You can gang Gem boxes for more cubic inches but the 14-50R won't be centered. Your best plan would be a 4" square deep and a mud ring or a surface 14-50R.

Paul

Basically, when EVs came about, Tesla and other manufacturers decied to use a receptacle rated for high amps that people already had installed in their houses (rather than requiring new EV owners to make new electrical installations), so they adopt the nema 14-50. But neither does Teslas nor does the one I have (Chevy Bolt EUV) require a neutral. Maybe, other EVs in other countries do require a neutral; but, the ones I know about do not require a neutral.

Yeah, that it does comply with code. But, in my case, it is safe and the charger is pre-programmed to only draw 16amps at 240V. I have too many things to do right now, so I have prioritize things; in the very near future, I will repace the cable for 8/3 nm-b (a neutral just for kicks) cable and will replace the 20amp+240V breaker for a 40amps or 50amps. For my needs, 30amps would enough. Besides, fast charging seems to degrade the battery bank faster based on what I read.


You asked about the box & how it was mounted.
The box is commonly called a "Gem" box. The real term is "Gangable Old Work Box Steel". The ears at the top and bottom keep it from falling into the hole.

What keeps it from pulling out are called "Madison Supports". The real term is "Old Work Box Support". Those are the folded over tabs that you see in the photo. If you re-wire and need to take the box out, bend the folded tabs back straight & the box will slide out. You'll most likely lose the Madisons in the wall, so pick up some new ones.


=> Good to know that, I will keep that in mind when the time comes to replace the box.

Yeah, the “Box Fill Requirements” was a concerned I had. Last time I installed a nema 14-50 (in a different house and situation), it was hard to fold and fit the then 6/3 gauge wires (I could have gone with 8 gauge, but…) in a 2-gang box and had to buy one with extra depth. It probably will be much easier with 8/3.

“Also note that a 14-50R & the appropriate conductors won't meet the Box Fill Requirements in the existing Gem Box. (Probably won't fit, either.) You can gang Gem boxes for more cubic inches but the 14-50R won't be centered. Your best plan would be a 4" square deep and a mud ring or a surface 14-50R.”

=> A mudring is something that may come handy in my situation. How about this one:

https://www.homedepot.com/p/Allied-...-Switch-or-Receptacle-Box-R9329-EWK/202536031

It is 4” (2-gang), for old-work, and 32 ½ cu in. Does it seems to be a good choice?
 
Please understand that I am not trying to be disrespectful. I also understand that you have time consuming obligations. However, please don't install the 50 amp device on a circuit with those conductors.


The A #1 Primary reason that putting a 50 amp receptacle outlet into a circuit with conductors rated for 20 amps is: Circuit Breakers Do Fail. In my career, I've replaced hundreds or maybe even thousands of circuit breakers that did not trip. They are mechanical devices and simply can fail. When they do fail, something burns.


You plan to never plug anything except a limited current draw device. As long as the current limiting circuitry, probably linear relying upon MOFSET control, maintains its function the device won't exceed the rating. But these fail as well.
I just repaired a current limited emergency circuit battery bank charger where the limiting failed. The thing was limited to 200 amps, but allowed 460 amps the be drawn. That surely would have been a disaster if the circuit fuse didn't open.

Thirdly, should someone come along later & want to plug something with a large draw in, how are they going to know the circuit is limited? Suppose a temporary space heater is needed, a welder, a floor polisher,... Hopefully the circuit breaker will trip and no one will be injured when it trips and whatever they are using quits.

And, warranty: Will the car & charger be covered since the charging current is limited?

The Big Worry: Consider Insurance
If there is a fire or injury and your insurance adjuster sees the 50a device being fed with 20a conductors and they find that you did it (no permit on record), You Are Sunk!

You not only will not get paid, you will owe a fire department invoice, be open to lawsuits by the insurance company and anyone injured or inconvenienced by the bad wiring job, etc. You will even have to pay the insurance company for the adjuster's time. (I've been called as expert witness zillions of times in tort and arbitration hearings. Trust me, the insurance company will win.)

Regarding if the box you linked will suffice (what came up was a box, not a mud ring), I don't know. I don't know how to figure conductor fill with 12 gauge wires and a 50 amp device.
Here's the math: 2.25 x 3 conductors + 2.25 for the ground + 2.25 for the internal clamp + who knows for the device. It is to be double the conductor size, but the conductors are under size. (2.25 x 2 is way less cubic inches than a 50amp receptacle uses.)

MAYBE FOR VERY, VERY TEMPORARY-
I should not even write this suggestion, but if someone is insistent upon jumping off of a cliff, at least offer some wings:

Perhaps you could make a FUSE Protected adapter to use temporarily. Be sure it is fuse protected, not circuit breaker protected. (Fuses never fail, which is why we use them on 13,200 volt and higher critical life-safety installations.)

Perhaps a fuse block safely inside a junction box on a cord will work. I'd suggest FRNR-20 Time Delay fuses. They put up with a lot of disturbances. I'm not endorsing this, but you are in a spot and need a charger circuit. This is the least dangerous thing that I can think of doing other than hiring an electrician & have a permitted & inspected circuit installed.
 
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Please understand that I am not trying to be disrespectful. I also understand that you have time consuming obligations. However, please don't install the 50 amp device on a circuit with those conductors.


The A #1 Primary reason that putting a 50 amp receptacle outlet into a circuit with conductors rated for 20 amps is: Circuit Breakers Do Fail. In my career, I've replaced hundreds or maybe even thousands of circuit breakers that did not trip. They are mechanical devices and simply can fail. When they do fail, something burns.


You plan to never plug anything except a limited current draw device. As long as the current limiting circuitry, probably linear relying upon MOFSET control, maintains its function the device won't exceed the rating. But these fail as well.
I just repaired a current limited emergency circuit battery bank charger where the limiting failed. The thing was limited to 200 amps, but allowed 460 amps the be drawn. That surely would have been a disaster if the circuit fuse didn't open.

Thirdly, should someone come along later & want to plug something with a large draw in, how are they going to know the circuit is limited? Suppose a temporary space heater is needed, a welder, a floor polisher,... Hopefully the circuit breaker will trip and no one will be injured when it trips and whatever they are using quits.

And, warranty: Will the car & charger be covered since the charging current is limited?

The Big Worry: Consider Insurance
If there is a fire or injury and your insurance adjuster sees the 50a device being fed with 20a conductors and they find that you did it (no permit on record), You Are Sunk!

You not only will not get paid, you will owe a fire department invoice, be open to lawsuits by the insurance company and anyone injured or inconvenienced by the bad wiring job, etc. You will even have to pay the insurance company for the adjuster's time. (I've been called as expert witness zillions of times in tort and arbitration hearings. Trust me, the insurance company will win.)

Regarding if the box you linked will suffice (what came up was a box, not a mud ring), I don't know. I don't know how to figure conductor fill with 12 gauge wires and a 50 amp device.
Here's the math: 2.25 x 3 conductors + 2.25 for the ground + 2.25 for the internal clamp + who knows for the device. It is to be double the conductor size, but the conductors are under size. (2.25 x 2 is way less cubic inches than a 50amp receptacle uses.)

MAYBE FOR VERY, VERY TEMPORARY-
I should not even write this suggestion, but if someone is insistent upon jumping off of a cliff, at least offer some wings:

Perhaps you could make a FUSE Protected adapter to use temporarily. Be sure it is fuse protected, not circuit breaker protected. (Fuses never fail, which is why we use them on 13,200 volt and higher critical life-safety installations.)

Perhaps a fuse block safely inside a junction box on a cord will work. I'd suggest FRNR-20 Time Delay fuses. They put up with a lot of disturbances. I'm not endorsing this, but you are in a spot and need a charger circuit. This is the least dangerous thing that I can think of doing other than hiring an electrician & have a permitted & inspected circuit installed.

You raised very good points and concerns, and I really appreciate your inputs.

While it is possible for such a catastrophe to happen, the odds for it to happen are very low.

Yeah, circuit breakers are electromechanical devices and they do fail (some fail far more often than others, like the federal pacific ones [stab breakers]). Devices such as chargers can also fail; but when they do so, they typically stop working; they almost never fail up (getting crazy and drawing more current than what they should). So, for both such events not only to happen, but to happen simultaneously during the very short period I am using that setup (maybe two months) – while possible – would be extremely unlike, especially if you consider that I use it (charge the vehicle) about 2 or 3 times per month.



Given that I charge the car two or maybe three times a month (so, very little exposure); and it is very temporary (maybe two months); it is not only very short term, but also done very sporadically. It would be different if, for instance, I was using it as permanent setup for ten year and charging the car everyday. Probably, the likelihood for mice (or other rodents) to cause a fire in my house in the long run is much larger than the current and very short term setup to cause a major fire ( if I was to build my own house, all wires would travel in EMT conduits). But, then, there is always risks in everything in life: when we leave the house in the morning to work (or anything else), there is no guarantee that we will be back.

“Thirdly, should someone come along later & want to plug something with a large draw in, how are they going to know the circuit is limited? Suppose a temporary space heater is needed, a welder, a floor polisher,... Hopefully the circuit breaker will trip and no one will be injured when it trips and whatever they are using quits.”

=> I am the only who lives and uses the house and garage. Yeah, if random people with Evs could use the garage, the situation would very different.

All my plans of install are based on using 8 gauge cable and a 40amps breaker. The current setup that is barely used and is a very, very short term thing ( 2 months or less).

And that scenario could apply for other situations as well. For instance, a normal 12V car battery charger (or other device or appliance) hooked up to an ordinary 15amps branch circuit could develop an internal short. In this case, if the breakers fails, then a similar danger would emerge (with exception of the insurance aspect of it).

One of the first things I will do when I come back from my trip (take off next week) is to go to the attic, install new install wires and replace the current breaker for a 40 or 50 amps breaker.

The fuse idea certainly add an extra layer of protection. Definetely, a great suggestion. I will look into it.
 

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