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Nema 5-20 outlet installations

tpham07

Active Member
Mar 21, 2017
1,965
2,396
Rhode Island
So my house was built about one year ago so i'm assuming all the wiring is up to code etc.

Anyways i was planning on installing my nema 14-50 outlet and i saw in my subpanel that the entire house is basically on 20A circuits, but every outlet in my house is a nema 5-15 outlet.

Since they're 20A circuits could i just replace a few 5-15 outlets in the garage with 5-20 outlets? i read somewhere that 20A circuits have to run 12 gauge wire, but i can't know for sure.
 

tpham07

Active Member
Mar 21, 2017
1,965
2,396
Rhode Island
Check the wire gauge. 20 amp needs 12 gauge wire. 15 amp uses 14 gauge wire.

Pretty sure its 12 gauge but ill check with the builder. Like i said i think its a code requirement to have 12 gauge wire along any 20 amp circuit, even if there are 15 amp outlets. ( i guess the thought being you can have multiple loads on the same circuit which can exceed 15amp but stay under 20 )

Install the 14-50 anyway. It's a whole different experience owning the car when you can get 29 miles/hr range plugged in vs. 5.

that's the plan. just want a backup in case of who knows what.
 

RichardD

Member
Feb 6, 2017
540
298
Texas
I had the electrician, Mr. Sparky load test the house, then decided what size breaker we could put in without putting undue stress on the wiring panel. There was room to add a 50 amp breaker without touching any of the other breakers. I would imagine you are in a similar position.
 

tpham07

Active Member
Mar 21, 2017
1,965
2,396
Rhode Island
Okay i know for sure the wires are 12 gauge now. When i went to go replace the outlets, the wires attached to the 5-15 outlet were too big to fit in the holes on the back you normally fit wires in (no doubt to prevent you from using too big of a gauge) and they were wired around the screws the old fashioned way instead. They fit perfectly in the back holes on the 5-20 outlet though :) problem solved. Good to know my builder followed electrical code haha, as they wouldn't give me a straight answer either way on what gauge wiring was used, and more of a CYA answer "consult an electrician"
 
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davewill

Active Member
Feb 5, 2014
1,829
2,079
San Diego, CA, US
Personally, I would still put in a dedicated outlet. You have no idea how many times the circuit was daisy chained before it reached the outlet you're using. If any one of those connections was poorly done or has worked loose, you could have a bad outcome.
 
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wws

Active Member
Aug 11, 2014
1,080
1,245
Northern California
Okay i know for sure the wires are 12 gauge now. When i went to go replace the outlets, the wires attached to the 5-15 outlet were too big to fit in the holes on the back you normally fit wires in (no doubt to prevent you from using too big of a gauge) and they were wired around the screws the old fashioned way instead. They fit perfectly in the back holes on the 5-20 outlet though :) problem solved. Good to know my builder followed electrical code haha, as they wouldn't give me a straight answer either way on what gauge wiring was used, and more of a CYA answer "consult an electrician"

Those 'back stab' holes save the electrician a few seconds per receptacle during installation. But for high current EV charging, the screws are better. Also make sure you use a 'spec' commercial grade receptacle. Just say 'no!' to those $0.39 residential grade cheapos.
 

tpham07

Active Member
Mar 21, 2017
1,965
2,396
Rhode Island
Those 'back stab' holes save the electrician a few seconds per receptacle during installation. But for high current EV charging, the screws are better. Also make sure you use a 'spec' commercial grade receptacle. Just say 'no!' to those $0.39 residential grade cheapos.

It was a commercial grade outlet so it cost me like $9, and it wasn't like a traditional backstab. This one you had to manually tighten the screws or the wires would pop out. But the outlet will probably be used once in a blue moon now that my nema 14-50 outlet is installed.
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,850
22,574
San Diego
While new construction typically has 20A breakers for receptacles, electricians still typically use 5-15 receptacles to save a few cents. Annoying, but easily replaced! To be fair, the Tesla charger is one of the few few devices I know of that actually has a 5-20 plug. All other high draw devices I've used, even big carpet cleaners that require 20A receptacles, use 5-15 plugs.
 

gregd

Active Member
Dec 31, 2014
2,596
1,812
CM98
It was a commercial grade outlet so it cost me like $9, and it wasn't like a traditional backstab. This one you had to manually tighten the screws or the wires would pop out. But the outlet will probably be used once in a blue moon now that my nema 14-50 outlet is installed.
Is this a new circuit? The only issue you might have is if the original wiring used the "stab holes" in a daisy-chain fashion. You might be using the screws, but unless the run is known to be direct to the panel (not shared), there is still risk that there's a loose "stab" upstream. It might test fine now, but over time if there's a loose one, it can oxidize and eventually burn up. Worth checking for, before you start drawing a lot of current for a long time (like you would when charging).
 

davewill

Active Member
Feb 5, 2014
1,829
2,079
San Diego, CA, US
Is this a new circuit? The only issue you might have is if the original wiring used the "stab holes" in a daisy-chain fashion. You might be using the screws, but unless the run is known to be direct to the panel (not shared), there is still risk that there's a loose "stab" upstream. It might test fine now, but over time if there's a loose one, it can oxidize and eventually burn up. Worth checking for, before you start drawing a lot of current for a long time (like you would when charging).
He already mentioned that the builder didn't use the holes because the 12ga wires didn't fit in them.
 

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