GFCI on NEMA 14-50

GFCI on NEMA 14-50

Did a Volker-search (thank you!) & did not find an answer to my question... I have an unprotected outdoor parking pad & am about to select from electrical bids to install the 14-50 outlet. Do I get a GFCI breaker? Will be a bit nervous plugging/unplugging in a downpour without it! What about maybe installing a main switch away from the plug?

Longhorn92 | 12 dicembre 2012

They say none required (, but I don't know if that means you shouldn't. I would contact them to make sure.

ghillair | 12 dicembre 2012

The outdoor high power outlets I am familar with, both marinas and RV parks always have a switch associated with the outlet.

Make sure switch is off, connect power cord, then switch on. When disconnecting make sure switch is off.

adufort | 12 dicembre 2012

I'm almost sure you must have a GFCI breaker for an outdoor outlet ... It would be very risky not to because a Child would risk électrocution trying to insert with metallic screw, toy...key In the outlet ...

jat | 12 dicembre 2012

I agree with @adufort - most codes will require GFCI outlets anywhere water can be present, which includes outdoor outlets. The mobile charger has a GFCI in it, but that won't help you for anything upstream of it (ie, plugging in a plug in the rain).

ReeceWeb | 12 dicembre 2012

I installed a GFCI breaker for my 14-50 outdoor outlet. It has not false tripped even a single time during the last 6 weeks of nightly use, including periods of heavy rain. Required or not, I feel better knowing there is extra protection on the line.

mallynb | 12 dicembre 2012

A GFCI will protect any outlet that is on the same circuit. Example: There is usually just one in a bathroom with multiple outlets. If there is a GFCI in the mobile charger, it should also protect the outlet at the other end of the charging cable when it is being plugged in. Codes vary in different states and cities. I’ve lived in a locale where a GFCI in the garage protected several outlets that were outside. Make sure your electrician or contractor is licensed. Specify that the installation complies with the appropriate codes. I’m an electrical engineer. That’s what I will do.

mallynb | 12 dicembre 2012

Correction. If there is a GFCI in the mobile charger, it protects the charger and passengers by removing power in the car, not the cable or the outlet.

jat | 12 dicembre 2012

@mallynb - a GFCI will only protect outlets downstream of it. The way it works is by detecting a difference in the current coming back on the neutral from what went out the hot line, so current leaking to ground upstream of the GFCI can't be detected.

dtesla | 12 dicembre 2012

When my 14-50 outlet was installed, it was installed without a GFCI.

solarpowered | 12 dicembre 2012

I called Tesla & was told that the UMC includes a GFCI that will try to automatically re-set after it gets triggered. Automatic re-set could not work if another GFCI in series was tripped.

adufort | 12 dicembre 2012

@ solarpowered

True but it is protecting the charger cable and the car but would not prevent a child getting electrocuted when the UMC is not plugged into the 14-50 outlet .. If the outlet is outside or inside where it can be played with by a child you really should put a GFCI !

dahtye | 12 dicembre 2012

The electrician who installed my outdoor NEMA 14-50 installed a dual 50Amp GFCI breaker in the main panel. I think it's a good idea since I get quite a bit of water where this outlet is. The outlet is covered and can actually be locked (but it's plastic, so anyone who is determined can get to the outlet).

kevjo | 13 dicembre 2012

I just had my NEMA 14-50 outlet installed on the outside of my house by an electrician and it passed inspection (Oakland, CA) There is a dedicated breaker of course but no GFCI.

jbunn | 13 dicembre 2012

I'm with Dahtye on this one. The GFCI protects everything downstream from the breaker. Putting it in the panel would be my preference.

dahtye | 13 dicembre 2012

Yep, it's easy. It comes on the circuit breaker. The Electrician just needs to purchase the 50A breaker with the GFCI button and connect it properly.

Robert22 | 13 dicembre 2012

Can I put a 60 amp breaker on a NEMA14-50 outlet? Using 80% of the 60 amps available would give me about 48 amps through the outlet not exceeding its maximum. Am I missing something?

dahtye | 13 dicembre 2012

That probably wouldn't pass code, but it is physically feasible. I'm not sure what the Tesla will do - currently it sets my charge rate to 40A (I cannot increase it), maybe due to the fact that I have the NEMA 14-50 plug on the cable or maybe it has a way to sense the type of breaker - I just haven't tried what you are asking.

Theresa | 14 dicembre 2012

Robert, Yes it would not pass code and there would be no benefit as the charge will only go to 40 amp. There is plenty of confusion as to how to get higher charge rates but the easy way to think of it is that unless you have the HPWC or the supercharger the max charge you will get is the 31 mph rate (i.e 40 amp). And it does not matter if you have twin chargers installed or not. Only the HPWC will use the twin chargers.

jat | 14 dicembre 2012

@Theresa - I understood that if you had a J1772 charger that went higher (the spec goes to 70A), then you could make use of the dual chargers that way.

SpeedyD | 5 febbraio 2013

@Robert22 - The 14-50 plug has a maximum of 40 amps, not 50.
You might think that a 40 amp plug would require only a 40 amp breaker. The thing is, the amp rating on a breaker is only for temporary/momentary loads. If you intend to draw current on a continuous basis, which obviously the Model S will do as it charges, you are only allowed to draw 80% of the momentary current rating through the breaker.

So, if you have a 40 amp breaker you can only draw 32 amps. The logical alternative is instead to install a 50 amp breaker, whose 80% rating matches the 40 amps the rest of the circuit is designed to handle.