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ra-san
Member
Makes no sense. Maybe he's thinking about how he's seeing two 110 breakers paired up or something - who knows.
If you are using the Tesla adaptor on the UMC, then it'll tell the car what to charge at - no need for you to set it yourself, unless you know that you have a bad connection of some sort that'd make you want to limit it down.
If you are using the Tesla adaptor on the UMC, then it'll tell the car what to charge at - no need for you to set it yourself, unless you know that you have a bad connection of some sort that'd make you want to limit it down.
dirkhh
Middle-aged Member
As ra-san says, most likely the two 110V breakers. Running 60A through a 14-30 outlet would be very dangerous. I'm sure FlasherZ will be here any minute and quote the chapter and verse from code, but fundamentally the plastic and the conductors in the 14-30 aren't rated for that amount of energy and it would most likely simply melt on you - or cause a fire.
jcaspar
Member
My guess is it's 2 40 amp breakers tied together, one for each leg of the 120v circuits to make 40 amps at 240v.
You friend is (hopefully) confused. If he's correct, than that "electrician" should return his license to the Cracker Jack box from whence it came. As mentioned, the 14-30 UMC adapter will auto select a max of 24 amps
Are these 2 single slot (120V) breakers? Maybe your friend is seeing a duplex (2 slot) 240V breaker and calling it "2 breakers"? If this was wired using two, 240V duplex breakers, than the electrician clearly doesn't even have a Cracker Jack license.
You can't legally run a 14-30 on one (or two) 40A breakers. And it wouldn't supply 60A without bad things happening.
Where did 60A come from, anyway? Why not 40A (breaker rating)? Or 80A (if, God forbid, these are 2 40A duplex 240V breakers in parallel:scared
I've heard of many L6-30 plugs melting/burning from not much more than 30A continuous. I would think 60A through a 14-30 is a guarantee of a fire.
This is not legal/to code, either. You can't parallel circuits for increased capacity, as you can't guarantee that each side carries their rated share and no more. For example, a loose connection in one of the circuits would increase the overall resistance in that circuit, and cause it to carry much less than half the load, thereby overloading the other circuit.
Which would still be illegal and a code violation - you can't connect a 14-30 to a 40A breaker. Also you can't use 2 individual single 120V breakers on a 240V circuit. You have to use a duplex 240V breaker.
As an aside, there is such a thing as a 14-60. It looks like a 14-50 with the neutral (middle blade opposite ground) rotated 90 degrees. It's a somewhat rare beast (I've never seen one in residential). There is no Tesla adapter for it.
Circuit breakers are placed on ungrounded conductors ("hot" wires) to prevent overcurrent. For 120V circuits, the current return is via the neutral conductor, which is unfused. Therefore, a single-width breaker is used. If it's a 30A breaker, it allows 30A to flow on the hot conductor. In the US, you obtain 240V circuits by using two opposing ungrounded conductors, which is why you need a double-pole breaker. NEC requires that the trip handles for 240V circuits be tied together, so that if one side experiences a trip or is shut off, that the entire circuit is de-energized. These breakers will frequently list the amperage twice:
That's a 40A breaker and will create a 240V/40A circuit, not 80A. You don't add them together, because the same current that flows through one conductor of that breaker also flows through the other side.
There is a way in which someone could parallel two circuits to create a larger circuit. It's dangerous, violates code, and is illegal in most places in the US. It would require two double-sized breakers in the box, and any electrician who does it needs to be demoted to bucket-carrier if it was implemented this way. I have to assume a true electrician wouldn't do it this way, and instead your friend was referring to a single 240V circuit.
As mentioned, by code, a NEMA 14-30 can only be placed on a 30A circuit, the use of a 40A breaker is a violation and is illegal. Maximum charging load on a NEMA 14-30 outlet is 24A per continuous load rules. Even 30A continuous on a 30A receptacle has been responsible for a significant number of melted receptacles in the past. The Tesla 14-30 and 10-30 adapters will limit current to 24A.
Charged just fine at 24 amps. I looked at the breaker box, the recepticle and the wire casing. It's a duplex 40 amp breaker. The recepticle says 30A on it and I plugged the Tesla 14-30 plug into it. The piece of wire casing is labeled: Romex E18679 SIMpull Non-Metallic Sheathed Cable 12-AWG 600 V.
This seems wrong!
This seems wrong!
Very wrong. Dangerously, so. The breaker is too big for the wire and the outlet. A 14-30 needs a 30A breaker (40 is too big, allowing you to overload the outlet). 12 gauge wire is too small for a 30A circuit. 10 gauge is the minimum for a 30A circuit. 12 gauge is only good for 20A intermittent, 16A charging.
Your friend should probably get his money back from the "electrician" who did this hatchet job, and hire a real electrician to fix it, before something bad happens.
You mentioned 12AWG above, which would be an issue. What color is the casing? Romex has been color coded for the last ~15 years. 10 ga/30A capable will generally be orange, 12 ga yellow, and 14 ga white.
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Googling "Romex E18670" shows references to 6ga through 14ga. I wouldn't interpret gauge from that marking.
E18679 is the standard Southwire/Romex part number for 2-conductor NM-B with ground. Some manufacturers will stamp a letter after "E18679" for the gauge, but it's not universal. The gauge of Southwire/Romex is listed immediately after "Romex(tm) Simpull(tm) AWG", such as "E18679F Romex(tm) Simpull(tm) AWG 12". Based on what you show here (although I know you said something else later), this leads me to believe that they put in 12-gauge wire for this receptacle. As noted, most manufacturers have begun to color-code the sheath for lower gauges -- #14 is white, #12 is yellow, #10 is orange. If it's a yellow sheath, that entire circuit has been implemented incorrectly. Otherwise, you'll have to find another way to look at the wire gauge.
No worries, you didn't mislead - then the only thing that is wrong is that he put it on a 40A breaker instead of a 30A breaker. If you swap the breaker out, you'll be ok. Maximum charging current is 24A. Because you used the Tesla 14-30 adapter, it automatically set that 24A for you.
Just to close this out, my friend went back to his electrician who said the 40 amp breaker is correct. I cannot convince my friend otherwise. The good news is that apparently the outlet will only be used to charge a Tesla which will limit the draw to 24 amps.
Thanks again for all of your help!
Thanks again for all of your help!
If you are ever at your friend's place again, please take a picture of his panel showing the "two 40 amp breakers" for that 14-30 receptacle. It is quite possible your friend, not being technical, is mishearing things. A picture would show us what is really happening.
His electrician is not licensed, then, or isn't subject to code enforcement actions.
The NEC is crystal clear about this:
First, the #10 conductor makes it a 30A circuit and it needs to be protected with an OCPD at 30A:
At least it's safer than most violations I see - the 30A breaker with the proper Tesla adapter will limit charging to 24A, which is appropriate. It *should* be protected with a 30A breaker, but if your friend and his/her electrician are standing firm, not much you can do.
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