Is there any code reason wiring a NEMA 14-50 with two lines and a neutral would be non-compliant?

Question

I have a commercial building with 3 Phase (120V / 208V) WYE to the panel.

We need to install a 3 phase NEMA: L21-20R outlet to run some equipment.

I have an electrician coming since I don't want to chase down the commercial breakers and bend conduit, and I got to thinking about adding an EV charger by the drive in door since the conduit bender and hole punch is already gonna be there.

Is there any code reason wiring up a NEMA 14-50 with two lines and a neutral would be non-compliant?

I don't know where my city is at in regards to the hardwiring versus plug in charger dispute, but I'd like the outlet there with all three hot lines and a neutral so we could swap the plug in the future. Worse case we would pipe out of the outlet into a hardwire charger if the code police called us on this, not a big deal.

The charger we have in mind operations 120V AC to 240VAC, so I don't see any electrical reason why the 208V at the NEMA 14-50 would be a problem?

Does the code have any opinion on this?

Am I correct the you can get 208V just using 2 legs of the 3 phase here?

Answer 1

(Someone may flag/close this as "not DIY". This is supposed to be "residential only". That being said, the exact same issues come up in single family homes, so I'll answer.)

Yes, you should be able to get 208V from two hots. But if the goal is EVSE, then do not put in a 14-50. Put in a decent hardwired box and call it a day. Or if you are not 100% ready to put in a charger yet, install the conduit and the box and either put in the wires or you can even add the wires and breaker later.

There are two big reasons to put in a hardwired charger rather than a 14-50 (or 14-30 or 6-30, etc.) receptacle:

• GFCI - This depends on your location, but based on the latest NEC, many jurisdictions now require GFCI on circuits, such as large 208V/240V circuits, that did not require GFCI in the past. Any good EVSE includes ground fault detection and automated reset, so by hardwiring you avoid the cost and possible problems of a large GFCI breaker.
• Reliability - You remove one major point of failure - the plug/receptacle. There have been quite a few reports of legitimate (i.e., UL-listed or ETL-listed) receptacles failing under the heavy and continuous load of EV charging.

Based on the quick move from a mix of NACS (Tesla) and CCS (everyone else) to NACS for almost everyone in the next 2 years, I would recommend a NACS (which mostly means actual Tesla right now) EVSE and anyone with CCS can use an adapter cable. The publicized plan from Ford and many other manufacturers is that they'll start shipping CCS->NACS adapters a year or so before they actually change the installed equipment on the cars.

Answer 2

First, the "conventional wisdom" is to install a 50A RV socket, I know. But that's because cars come with travel adapters for charging at RV parks. It's not a best practice for home (too fast) or workplace charging (too fast, or sometimes, too slow).

I say that because one guy in the news spent over $12,000 on service upgrades and installing The Fastest Charge Possible (tm) at home and work, and 90% of that was wasted on overkill. Don't like to see folks waste money.

Now hardwired wall units are a win for a several reasons.

• it deletes both a costly GFCI breaker and also a costly (and frequently melted) RV socket. Using the cheapo sockets has not worked out for people.
• it's much easier to "dial-a-speed" to suit your NEC Article 220 Load Calculation on your panel. Both faster and slower.
• it permits using energy management (such as Wallbox's Power Boost) to completely ignore the Load Calculation and charge as fast as you like.
• it saves a wire (EVs don't use netural, but RVs do, and if you stick an RV socket on the side of a building, it must have neutral so you don't fry an RV).
• people's charge cables don't get stolen.

So with that covered... I am happy to say #8 THHN will suffice for a 50A EV circuit if it is alone in the conduit. Otherwise, #6 will suffice for up to 60A for up to 3 circuits in the conduit. For 100A circuit for those big F150 Lightnings and whatnot, #3 copper.

You are correct that EMT shell provides grounding.

On a 208V panel (this is one, right?) the 2-pole EV breaker installs exactly the same as in a 240V panel. If I was advising a residential electrician who was installing such a circuit, the only thing I would advise is check voltages to ensure none of the wires are more than 120V to ground - that would be wild-leg 240V and you don't want that leg.