rhumbliner
Member
the price difference is only 20 cents a foot.
Electricians are expensive. Wire is not. You’re trying to save $7?
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the price difference is only 20 cents a foot.
Thanks for this level of detail.
I'm using 8AWG Romex that shows rated for 90C. This is run through walls (inside).
I have it wired up now to a 40a breaker, but I was thinking of putting in a 50a breaker for the Tesla
I use the same 40a setup on our PHEV with a 32a Siemens Versicharge without issue.
Link to cable:
Southwire 125 ft. 8/3 Stranded Romex SIMpull CU NM-B W/G Wire-63949202 - The Home Depot
Product documentation shows max Amperage on the cable @ 40a, so I was thinking the UMC1 would work.
Why not just folllow Tesla’s installation instructions as posted above (post #4). They specify the wire and breaker sizes for a NEMA 14-50 outlet for the UMC. Tesla has a similar document for every outlet type, linked from the home charging page. Don’t try to reinvent the wheel, RTFM instead.
Because that is NM wire (Romex), NEC says you must use the 60c rating instead of 75c or 90c even if that is what is labeled on the cable. So that wire is only good for up to 40 amps.
Electric Vehicle Chargers are considered "Continuous Loads" under the NEC and so you must size the wire and circuit breaker 25% larger. So for a 32a charger you need a 40a capable wire and breaker. For a 40a charger you need 50a capable wire and breaker.
So please do not just switch the breaker to 50a! That would be dangerous and not code compliant. Note that the new UMC Gen 2 that ships with all new Tesla's now is only 32a so it would be fine on a 40a circuit.
He probably recommended #8 because it’s easier to pull through conduit than thicker wire. Laziness is a powerful motivator.
He probably recommended #8 because it’s easier to pull through conduit than thicker wire. Laziness is a powerful motivator.
Don’t buy a Tesla and the skimp on the wire. Buy a Bolt and skimp. What’s the price difference? $30? $100? If it’s a $100 I would skimp to get it down to $30. But that’s just me.
I get your concern, but the fact is that it's to code, and it's even the recommended install for a number of 30-32a J1772 EVSEs out there (like the one I own). My take is that people should install a 50a circuit if they can, but if their service or existing wiring can only handle 40a, then go ahead and do that.This is an old thread but one thing I read here really concerns me is that ppl are putting a 40 Amp breaker on a Nema 14-50 outlet. Even though the Gen 2 mobile connector only pulls 32A in theory necessitating a 40A breaker, the expectation of a Nema 14-50 outlet is that it is 50 A amp capable. The next owner of the house may plug in a dryer, welder, or compressor expecting a 50A circuit with a 50 A outlet for 40 Amp continuous service (there is a 20% derating between peak and continuous). It is dangerous to undersize the breaker as a future device may pull 40A continuous, tripping (best case) or worse overheating the the undersized 40 A peak breaker. An overheating breaker can lead to a fire caused by the resistance heating.
If installing a HPWC set to 40A for a 32 Amp continuous draw, then the 40 Amp breaker is permissable as the device is permanently wired to the 40 Amp device and will not be disconnected to operate a device of higher and lower current.
Yes, that is the most common, standard way of doing that.So... I'm running a 14-50 outlet. The run to my breaker box is four feet. I used 6ga Romex and a 50a breaker. The outlet is inside a dedicated box housing. Assume I'm good? Thanks
This isn't enough information to answer by just telling the wire gauge. Different types of wire or cable have different amp ratings, so you haven't given enough of a description of exactly what it is to tell. Is this separate wires run though conduit? Or is it that a whole cable that has several wires bundled together inside a tight rubber sheath? 8 gauge would be acceptable if it's separate wires in conduit, but not acceptable if it's NM-B cable.used an 8 gauge wire.
Connected them where? If they are just tied together in the outlet box, then that is definitely wrong. They need to stay separate all the way back to the main panel in the house. If that main panel, then yes, ground and neutral can be interchanged and tied together there (and ONLY there).I noticed later that he hasn't used the separate ground, instead, he connected the ground and neutral (white wire).
Thank You so much for the quick reply. Yes, there are 3 separate cables. Black, Red, and White. The wires running from the electric panel to NEMA14-50 is just 1 ft. long and all wires are separate but the gauge is 8. Is that enough to charge my Tesla Model Y(which is delivering next month).? My main concern is neutral and Ground wire since it is connected with a small 2-inch wire in the NEMA receptacle. Is that safe?This isn't enough information to answer by just telling the wire gauge. Different types of wire or cable have different amp ratings, so you haven't given enough of a description of exactly what it is to tell. Is this separate wires run though conduit? Or is it that a whole cable that has several wires bundled together inside a tight rubber sheath? 8 gauge would be acceptable if it's separate wires in conduit, but not acceptable if it's NM-B cable.
Connected them where? If they are just tied together in the outlet box, then that is definitely wrong. They need to stay separate all the way back to the main panel in the house. If that main panel, then yes, ground and neutral can be interchanged and tied together there (and ONLY there).
You didn't mention a conduit, but there should be some if they are individual wires. But yes, if those are separate wires, 8 gauge is acceptable for a 50A rated circuit. If you look up in the table here, the wires in conduit would be THWN or THHN, those both have a rating of at least 50A. So the thickness of the wire would be OK, but only 3 wires is definitely a problem.Thank You so much for the quick reply. Yes, there are 3 separate cables. Black, Red, and White. The wires running from the electric panel to NEMA14-50 is just 1 ft. long and all wires are separate but the gauge is 8.
But this is still a problem. A 14-50 outlet MUST have 4 wires to connect it properly. Do you mean that the white wire goes to it, and then it uses a small 2 inch wire to basically "jumper" the neutral and ground pins together on the outlet itself? That is definitely wrong. Neutral and ground each need to have their own separate wires running all the way back to the panel. The ground wire is allowed to be much smaller and can be a bare copper wire that's not insulated, but it does need to be there.My main concern is neutral and Ground wire since it is connected with a small 2-inch wire in the NEMA receptacle. Is that safe?
I think it just needs a ground and the two 120V wires to be able to charge at 240V. I find it strange that he didn't run a green ground wire. Is this in a conduit? Is the box that the receptacle is installed in, metal? You should definitely have a green ground wire attached to the receptacles ground terminal.Thank You so much for the quick reply. Yes, there are 3 separate cables. Black, Red, and White. The wires running from the electric panel to NEMA14-50 is just 1 ft. long and all wires are separate but the gauge is 8. Is that enough to charge my Tesla Model Y(which is delivering next month).? My main concern is neutral and Ground wire since it is connected with a small 2-inch wire in the NEMA receptacle. Is that safe?
Yes, an EVSE only needs the two hots and a ground. But it's a 14-50 receptacle, which is required to have a neutral. The car won't care if there isn't a neutral connected to the neutral lug in the receptacle, in fact I don't believe the neutral pin is connected to anything in the mobile connector. But something else like an RV or electric range would DEFINITELY care if the neutral isn't there. A floating neutral will burn up all sorts of things in something expecting it to be there. If you don't want to run a neutral, install a NEMA 6-50 receptacle instead.I think it just needs a ground and the two 120V wires to be able to charge at 240V. I find it strange that he didn't run a green ground wire. Is this in a conduit? Is the box that the receptacle is installed in, metal? You should definitely have a green ground wire attached to the receptacles ground terminal.
Why? A 120V device is the only thing looking for a neutral. If the neutral leg isn't there, the device simply wouldn't get power.But something else like an RV or electric range would DEFINITELY care if the neutral isn't there. A floating neutral will burn up all sorts of things in something expecting it to be there.
Most appliances use a 14-50 because they need both 120v and 240v. Unfortunately, leaving the neutral out does not necessarily mean the 120v parts simply get no power. Instead the return voltage can find it's way through other parts of the circuit to the other leg or to ground.Why? A 120V device is the only thing looking for a neutral. If the neutral leg isn't there, the device simply wouldn't get power.
As for this installation, with such a small run, it seems there wouldn't be much reason not to run the 6 ga wires and have a proper ground. Even replacing the wires at this point would be trivial.