HELP: 14-50 Nema outlet trips 4 times before it works?? (Update: RESOLVED)

HELP: 14-50 Nema outlet trips 4 times before it works?? (Update: RESOLVED)

Sorry if its double post.. I tried posting couple days ago but did not see my post.

I got 14-50 Nema outlet installed in my garage to charge my Model 3. Few days ago I got my Model 3 and charging has been a nightmare.
In short: While charging, the outlet trips 4 times before it works fine. I have to reset every 10 minutes when it trips.
Outlet was installed by Tesla recommended electrician (Gunnar Electric, MN) where the electrician installed 50 amp circuit breaker and ran conduit across the other side of garage. Main panel is in garage and the house is relatively new (2014 construction). I used to have electric water heater which was converted to gas and the electrician used that 50 amps to run the wires. I have tried reducing amps to 30, 24 and 10 but the problem persists. Called electrician who promptly sent a guy to check it out.. the guy came and thought it was a bad circuit breaker.. replaced it with a new one (150 amps eaton circuit breaker). But the problem did not go away. The electrician checked out everything including thermal heat on the wires. He did not find any other faults.
I am at loss... every time I drive around and come back home to charge, it trips every 5-10 minutes for 4 times and then it works fine until unplugged. Unplug, drive and come back, same problem. The electrician thinks I may need Tesla Wall connector but will it work? I have already spent $800 on this electrician (install). Tried at 10 pm when nothing else runs in the house and I have same issue of tripping 4 times. what gives? Talked to Tesla rep, told him the situation and he mentioned its electrician stuff and nothing with the car.
Any pointers/suggestions on how to proceed with this problem? Weird it works after 4 trippings (load is balanced at that point)

Frank99 | 5 november 2018

You've had the Electrician out to re-check his work. Let's look at the next possible problem: the UMC. My suggestion is to take your car and UMC to the service center (or a friend's house with a functioning 14-50), and plug it in to charge there. If the breaker trips, the Service Center needs to deal with the problem - you either have a bad UMC or a bad onboard charger. If it doesn't, you need to drag the electrician back to recheck every connection they made, and hook up a current monitor to check how much current is being drawn.

The fact that it takes 5-10 minutes kinda suggests a bad circuit breaker. But, if they've already replaced it, it seems unlikely that there would be two bad ones.

Frank99 | 5 november 2018

Also, I think the standard Water Heater circuit is 30A. I'd ask the electrician what gauge wire was installed - it was probably AWG 10, but could have been 8. It needs to be 8 or 6.

Wade406 | 6 november 2018

The 50 amp breaker on the circuit the electrician installed is not the one that's tripping? You mentioned the breaker he replaced is a 150 amp breaker. Is that a typo or did he need to replace your main breaker?
Breakers are designed to only trip so many times and then they are weakened. You're tripping this a lot.
If you can try a different UMC, or find another location with a NEMA 14-50...
Also, since you have tried lowering the amps settings, try plugging it in to the 120 volt outlet and see what happens.

reed_lewis | 6 november 2018

Did he install a GFI breaker? That might be the issue.

skappag | 6 november 2018

Thanks all.
Sorry, 150 amp was the main breaker. The GFI breaker is tripping... excuse me for my electrical knowledge(no idea about electrical stuff).
Currently my car is in the shop going through PPF, Coating, Tinting. I have made an appointment with Tesla to make sure UMC/on board circuit is not at fault. I will plug in for 30 minutes at their site and if it trips for any reason then Tesla owns it.
Talked to my electrician who will then come and replace the wires and check all the pertinent stuff again.

skappag | 6 november 2018

btw, 6 guage wire was used. Can't wait to get the car which seems so long (Friday) and try out few things.

reed_lewis | 6 november 2018

Car chargers do not like GFI breakers.

bp | 6 november 2018

Recommend you phone Tesla customer support and ask to talk with someone from their charging team. They should be able to provide advice on using GFI/GFCI with UMC and a 14-50 outlet.

kcheng | 6 november 2018

Well, you want to try to isolate the problem. If you have a friend with a Tesla, bring em over and try out your charging setup. If they have a UMC, try your car with their cord.

Also, I'd look at your ground, make sure it's grounded properly. | 6 november 2018

I'll add that having a GFI on a GFI may be the cause. A GFI is not required (or desired) on a NEMA 14-50. The Tesla UMC has a built in GFI. So it may be the two GFIs are tripping up each other. Change over to a non-GFI 50 amp breaker and I bet your problems will disappear.

skappag | 6 november 2018

Thank you all... will let the electrician know all the suggestions; mainly GFI breaker not required and wire grounded properly....

skappag | 6 november 2018

Thank you all... will let the electrician know all the suggestions; mainly GFI breaker not required and wire grounded properly....

Frank99 | 6 november 2018

I believe that the 2017 version of the NEC requires a GFCI for an outlet intended for EV charging. There is a lot of confusion about what did and didn't make it into the final version, and your state may not have adopted the NEC yet, so your electrician (who sounds like a pro who knows what he's doing) is probably the best resource as to whether or not one is required.

I'm not an electrician, and don't have access to the NEC, so I can't check. I'm relying on:
which seemed to have the most authoritative answer I could find...

DonS | 6 november 2018

Most EV chargers (based all of the handful I've seen) have their own GFI circuit, AND IT CHECKS IT.

Before the start of charging, the EV charger purposely sends a small current to ground as a check that the ground is really connected. This is a protection against an open ground, where a fault could possibly electrify the entire car body.

That ground checking step in an EV charger will trip an upstream GFI/GCFI.

Bruno442 | 7 november 2018

GFCI is not required the 14-50 outlet even though it is installed in a garage. That GFCI breaker probably cost you 3x the price of the standard 2 pole 50 amp breaker.

jordanrichard | 7 november 2018

Why was a GFI breaker used. Unless your outlet was placed near a sink in your garage, a GFI is not necessary, except maybe to pad your electrician's wallet.

DonS | 7 november 2018

I think there is confusion because GFI protection is required for EV charging, but having it twice, in both the charger and the breaker, is not required and will cause problems as found by the OP.

skappag | 7 november 2018

Thanks all.
I have been following up with my electrician letting him know that GFI exists on Tesla UMC and not required on the panel but he insists GFI is mandatory and must be installed according to code else our local inspector would not certify.
Since he is Tesla recommended he says, no where in the classes or manual it says the second gen Model 3 UMC has internal GFI.
Anyone knows where I can find second gen UMC specifications where it mentions GFI?

PrescottRichard | 7 november 2018

Check your Tesla account on the page that has your car- there are all kinds of .pdf docs linked at the bottom. Maybe one there would have the info you want?

GHammer | 7 november 2018

The manual shows two different error codes for ground fault and ground detection. It most certainly has ground fault protection.

DonS | 7 november 2018

I found the proposal to modify 2017 NEC article 625 to include GFI protection on all outlets for Level 1 and Level 2 chargers. The purpose is to protect a person plugging and unplugging an EV charger, particularly in damp or wet locations. I couldn't find any evidence that this proposal was accepted.

If this does come to pass, EV chargers will need to be redesigned since the older ones will not work with an upstream GFI.

Yodrak. | 7 november 2018

"Anyone knows where I can find second gen UMC specifications where it mentions GFI?"

No, but I can tell you where to find a 50 amp circuit breaker to replace the GFI breaker the electrician installed in your panel, and it's easy to make the change. | 8 november 2018

This is the Gen 1 manual:

Here's the Gen 2 manual:

Both manuals do not directly talk about GFIs, but as @hammer points out, it does show GFI error codes.

zbrandt | 8 november 2018


skappag | 8 november 2018

Thanks again. I am sending these over to my electrician.
He said he will send someone early next week and I am going to ask him to replace the GFI breaker with 2 pole 50 amp breaker to test it out even if he insists removing GFI breaker violates the code.
What is the worst that can happen if he removes GFI breaker? Since I am a noob, is it a fire hazard?. From what I understand the equipment/personnel is protected from the breaker on UMC.

milesbb | 8 november 2018

The GFI breaker is required for a 14-50 outlet in the 2017 NEC. It may take a while for some states to adopt this but it will become a requirement for new installations. If you get your 14-50 installed before local authorities adopt the 2017 you should be grandfathered . The GFI protection in the UMC does not replace this requirement. The code requirement is:

NEC 625.54 Ground-Fault Circuit-Interrupter Protection for Personnel. All single-phase receptacles installed for the connection of electric vehicle charging that are rated 150 volts to ground or less, and 50 amperes or less shall have ground-fault circuit-interrupter protection for personnel.

Note the 14-50 has two legs that are both 120 volts to ground so it is included in this requirement. The cost of a 50 amp GFI two pole breaker, about $150 vs $15 for a standard breaker may convince a lot of folks to go with the HPWC. The HPWC installation does not require the GFI breaker.

Breaker manufactures cut a fat hog on this new requirement.

DonS | 8 november 2018

Without a GFI breaker, the possible danger is to a person standing in a puddle when plugging or unplugging the charger. This shouldn't be an issue, but in the event of frayed insulation or touching the outlet prong, the GFI offers protection.

Incidentally, this addition of 625.54 is listed as tentative. "A Tentative Interim Amendment is tentative becau
se it has not been processed through the entire standards-making procedures." So I question whether it is even a standard yet.

Frank99 | 10 november 2018

As far as I can tell, the published version of the 2017 NEC contains 625.54.
It really pisses me off when I can't tell how to follow the law without paying someone $120 for the proprietary sections of the law...

skappag | 16 november 2018

UPDATE from this morning (11/16): After going back and forth, the electrician came and removed the GFI breaker and voila it has not tripped for the last 4 hours its been charging. Electrician is baffled but happy that its finally working for me.
Thank you all for very helpful suggestions.

GHammer | 16 november 2018

Baffled? It's not that hard to figure out, part of the UMC's test to see if there is a ground is to run a very small current through it. This test current is enough to trip some brands of GFCI's.

Donz_S | 16 november 2018

Very interesting reading. Thank you all for your contributions.

DanFoster1 | 17 november 2018

@hammer @OR-US +1

I agree with 100% — how in the world could a licensed electrician be ‘baffled’ by such a thing as this? If one installed any GFCI downstream from another GFCI, the same thing would happen! Tesla owners on this forum solved the case before the electrician—even after multiple trips to the OP’s installation! He also apparently trained for this but didn’t know the UMC has it’s own (among other things) ground fault testing, seriously dude? Interpretation of fault codes is in the manual!

More generally I’m concerned that the new NEC rule requiring GFCI breakers for NEMA 14-50 outlets will make charging from these outlets impossible in cases of new and recent construction. It seems clear that nearly all GFCI circuit breakers will trip in response to the tiny current the UMC uses to check for proper ground.