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Charging Installation : Amp of circuit breakers and gauge of wire

1170 Views 5 Replies 5 Participants Last post by  dafish
Before I call the electrician for the instalation of the charger, I would like to know how many amp of circuit breakers and what number of the gauge of wire should I use on my Ariya charger installation?
  • 50 amp breaker with 6 gauge for Wallbox 48A? hardwired
  • 40 amp breaker with 8 gauge for Wallbox 40A? plug-in
  • or even bigger for each of them.?
Also, are there better brands for NEMA 14-50 receptacles that you recomend to use? Are there better quality brands for cables/wires?
Thanks for your help
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For my Tesla wall connector 48 amp max a 60 amp circuit breaker was code required. Multiply your max connector power by 125% to determine your breaker size. A 40 amp connector would need a 50 amp breaker. Same goes with the Nema plug if you want to be safe. Read somewhere on the internet to use a commercial built plug rather than something from Home Depot but I cannot attest to that. Make sure your electrical panel can handle the extra load. An electrician can determine for you. Don’t know about gauge wire size. I am somewhat handy around the home but I had qualified electrician do all the installation. I don’t mess with electricity!

I plan to use the wall connector with my Ariya whenever it arrives in 2023!🤨. I understand the Ariya would limit the charging rate of the Tesla connector since it charges slower than my Model Y. I can also dial down the amperage output on the wall connector from the Tesla app if necessary.
I installed 40a, 8gauge wire for the plug in wallbox - it draws 31a.
Industrial grade receptacle is a must of using a receptacle but check every 6-9 months.

You can't use a 50A breaker on a 48 charge circuit. You must derate everything by 80%, or multiply load by 1.25 to get required circuit capacity.

48 amp EVSE needs at least 60 amp capacity circuit.
40 amp needs at least 50 capacity.
32 needs 40
24 needs 30

In truth wire gauge is supposed to be corrected for heat (let's say you're passing through an attic in a hot climate), but I seem to the only guy that knows it. No electrician I've ever contracted with knew or cared. For single circuit pulls you can save considerable money using aluminum, but know the bend radius can be a beach. Here is an ampacity link:

nec ampacities.pdf (
Ampacity Charts | Wire Gauge Chart | Cerrowire

What ends up happening is we're in a no-mans-land when looking for a 48a continuous circuit. Some for instances that would work.
4/3 NM copper will do, but its pretty expensive.
6-6-6-6 SER would work too, and it should be cheaper.
4-4-4-6 Aluminum works too and is something like 1/4th the price, but it can be hard to find.

At this moment I'll do one of the latter two, mostly depending on what the electricians have, will do, etc. This as I'd rather not get into me buying cable in advance and most electricians are pretty narrow in what they keep in hand.

And yes, if 14-50 and you're going to be using them to capacity you really want a commercial grade plug.
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