Question about NEMA 14-50

[Skr1988]

Good evening. I recently had an electrician come out to install a NEMA 14-50 outlet in my garage for my Model 3 I get next week.

He installed a 14-50 outlet using a 40 amp breaker, and 8 gauge wire rather than the 6-3 gauge. The outlet is about 1 foot away from the breakerbox.

Is this a problem? Should I have someone come out and redo the installation? This electrician said the wire and breaker combination would be fine.

Thanks for any assistance!

 

[skriefal]

It should work okay if you don't draw more than 32 amps continuous, and assuming that the electrician hooked things up correctly. But I wouldn't want a 50-amp 14-50 outlet on a 40-amp breaker or with 8-gauge wiring. Hopefully it was cheap!

 

[miimura]

This is legal and safe with the included Mobile Connector since it only draws 32 amps. However, don't use another plug-in EVSE that can draw 40 amps. The electrician should have given you the option for the full 50 amps versus the 40 amps he provided.

 

[Kevy Baby]

Worth throwing in that the Corded Mobile Connector is capable of up to 40 amps, assuming your car can handle it (the SR and SR+ models are maxed at 32 amps).

Personally I think it is short-sited thinking (and potentially dangerous) to leave it at the 40 amps: I would have it corrected.

 

[jjrandorin]

You should have that electrician explain to you in something other than "it will be fine" why they did what they did. Whether this matters or not sort of depends on what model 3 you are getting. The SR+ only charges at 32amps max on a L2 connection (which your 40 amp breaker setup will do).

The real question is why did they do it that way (load calculations? Cost?). If you wanted a 50amp breaker connected to the 50 amp 14-50 along with the appropriate wire, and they didnt do that, you should have stopped them and asked "why" and either told them what you expected right then or had a better understanding of why they did it that way (what you were paying for).

 

[Scrannel]

Right after I got my M3P and realized 120v wasn't going to cut it, when to my local electrical supply. (In Los Angeles one is allowed to DIY and permit later) They asked what the car was. Box rating. How far was the throw etc. Then handed me 6' of 6-gauge Romex and a 50 amp breaker. I attached to a high-end 14-50 outlet where I keep my UMC permanently plugged-in. Doesn't even get warm. It was odd walking into an electrical supply and have the over-the-counter guy know a lot about EVs already. But, that's Los Angeles. Maybe electrical shops will become the new Pep Boys.

 

[Sophias_dad]

While its allowed, its just stupid of the electrician to wire it up that way. It saved him $5 in wire, and nothing for the breaker.

 

[Dmagyar]

Just thinking if it was #8 thhn in conduit (not romex) that’s allowable to carry the 50 amps, but the breaker definite too small.

 

[Sophias_dad]

allowable to carry the 50 amps

Good point! So the difference is that the electrician most likely doesn't carry a 50 amp breaker for OP's panel on his truck. Sigh.

 

[Gauss Guzzler]

He installed a 14-50 outlet using a 40 amp breaker, and 8 gauge wire rather than the 6-3 gauge. The outlet is about 1 foot away from the breakerbox.

That is completely legal, completely safe, and completely adequate for your purposes at this time.
It is not ideal however because you'd need 6AWG and a 50A breaker if you ever change to a 40A portable charger or convert the outlet to a junction box for a 40A capable wall charger.

As others noted, this probably happened because he only had a 40A breaker handy at the time. There's no meaningful cost difference and likely no limitations from the main panel.

 

[Sophias_dad]

you'd need 6AWG

Not if its individual conductors in conduit. Heck, with that short a run I think its legal to run NM-B through the conduit(although then you need to consider the 60C limit of the NM-B, which means 6awg would be needed).

8 awg THHN in conduit is good for 50 amps. That said, I'd probably go bigger anyway.

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com