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Many times when I plug in my Tesla, the GFCI 5-15 outlet in our garage trips, killing the whole circuit. It usually works fine after resetting the GFCI and trying again. This happens whether or not I have the charger plugged into a regular outlet or the GFCI one.

I've read that GFCI outlets "get old/wear out" over time and become more sensitive, and this one is likely at least 6 years old. Something about Tesla charger testing out the ground when starting to charge? Would it be a good idea to try and replace it? It appears it's on a 20amp circuit (at least, all breakers in panel are 20amp+), so I should be alright going with a 5-20 receptacle while I'm at it, correct? Might as well get a little extra amperage if I'm going to replace it anyway.

Update: I purchased a new 5-15 outlet and installed it, have had no issues since.

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  • You do NOT "get a little extra amperage" by upgrading the outlet! If the breaker is 20 amp and the wiring is 12 gauge, then yes, you can put a 5-20 receptacle on it. If the wiring is 14 gauge, then you must switch to a 15 amp breaker (no matter what outlet's on it). That said, yes, GFCIs do break down over time, so it may not be a bad idea to replace it. Make sure you take a picture before you remove any wiring from the existing receptacle - it will save you many headaches putting it back together. Make sure you wire the new one exactly like the old one. – FreeMan Nov 23 '20 at 18:39
  • I recently moved into this place and am not sure what the wiring situation is like for sure. Just know I have a 5-15 currently and a 20 amp breaker. I will check the wiring (after switching breaker off) to confirm what is in the walls before purchasing a new receptacle to try – Havegooda Nov 23 '20 at 18:42
  • If it was built in the last 20 years or so, 14 gauge NM-B will have a white jacket and 12 gauge will have a yellow jacket. That's the jacket surrounding the 3 individual (black/white/bare) wires. If you have a metal box and metal tubes running out from the boxes, that's conduit and you'll need to look at the individual wires to read the labeling on them. – FreeMan Nov 23 '20 at 18:46
  • Have you tried plugging the charger into a different GFCI? Does it trip only when the car is connected, or does it trip the GFCI even with the car unplugged from the EVSE? – ThreePhaseEel Nov 23 '20 at 23:54
  • A GFCI is very unlikely to fail in just 6 years. I have some outside that are at least 15 years old, maybe as much as 25, and they work perfectly fine, even with high-amp devices like a leaf blower. – Steve Sether Nov 24 '20 at 2:06
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1 - If this is a 20A circuit but the device is designed for 15A (two straight up prongs instead of one up, one sideways) then changing to a 20A receptacle will make absolutely no difference.

2 - GFCI tripping, in some circumstances, is due to an actual failure of the GFCI itself. I don't think 6 years old is all that old (I have some that are 20 years old and working just fine), but replacing it may have some effect. A GFCI in a garage is likely subject to extreme temperatures which can affect lifetime.

3 - GFCI tripping, in most circumstances, is due to a failure of the device you are plugging in or due to moisture. Make sure that the plug/cord is totally dry before plugging it in and that there are no exposed conductors, crimped cords, etc. that could be the source of a real problem.

4 - Charging a Tesla, or any EV, off a 5-15 receptacle is extremely limiting. Going up to a 5-20, provided the charger will actually make use of it (which should mean that it has a 5-20 plug, which is actually quite unlikely because of other better options) would increase charge rate by 33%. But going to a 6-20 (20A 240V) would more than double your charge rate and going up from that to a 14-50 (50A 240V) will give you a LOT more charging capacity. See the Tesla manual for details.

Upgrading the receptacle (beyond 5-20) will require new wiring. How easy or hard that will be depends on:

  • Your total electric service - i.e., whether you have enough capacity or need to get a utility upgrade
  • Space on the panel for a new double-breaker
  • Work involved running a new circuit from your panel to the garage

But long term, it will almost certainly be worth the effort. It can easily make the difference between being able to charge overnight after a long trip vs. getting up in the morning and finding you are only at 25%.

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  • I would add one thing: if the OP sticks with the existing wiring and outlet, he should set the max amperage his Tesla is allowed to draw to 19A max (this is an onboard setting via the touchscreen control panel) – Carl Witthoft Nov 23 '20 at 19:18
  • Actually, that would be wrong. Assuming a 20A circuit, the max. draw for a continuous load (and a low-charge-rate Tesla could go for 12 hours at a time) is 16A. If the default is 12A then bumping up to 16A would make sense, though might be skirting the rules technically given a 5-15 connector. Though realistically if it is a 20A circuit then that would not actually be a problem. – manassehkatz-Moving 2 Codidact Nov 23 '20 at 19:20
  • Is that a code limit? If there's significant voltage drop above 16A, the car will automatically reduce the input current level until the voltage returns to nominal. I don't know what a M-3 's automatic max when plugged with a 15A adapter (part of the Tesla cable); I know my M-S, with the NEMA14-50 connector hard-limits at 40A – Carl Witthoft Nov 23 '20 at 19:22
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    @CarlWitthoft It is a code limit. I'm no expert, but I have seen it mentioned many times. Not voltage drop. The 40A on 14-50 is exactly the same - 40A = 80% of the 50A breaker. As I understand it, the basic idea is wires heating up under long-term use. – manassehkatz-Moving 2 Codidact Nov 23 '20 at 19:39
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    Thanks for the response. I'd change it from a 5-15 to a 5-20 which the tesla charger has an adapter for. 15amp to 20amp isn't a huge difference but since it sits for at least 14 hours a day usually, an extra couple mph charge rate would make a difference. Considering putting in 240v but since we're renting I'm hesitant to put the money into that. I've tried two chargers, first one was broken but they gave me a brand new one the next day which I've been using successfully. I'd love to go to 6-20, but there's some minor networking equipment (~50w?) on the same circuit, so 240v is a no go there – Havegooda Nov 23 '20 at 21:47
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Most chargers have large transformers in them when they are unplugged for a period of time the caps in the charging circuits are discharged and when plugging in the transformer and caps have to “charge up” this creates a large momentary draw on the electrical system and I have seen chargers rated for 15 amps trip 20 amp breakers I have recreated it many times in a row for a home owner that did not believe this was the case. Leaving the charger plugged in the coils remain excited and the caps are charged up.

The large spike may be returning some of the power on the ground verses the neutral it happens with large spikes even with no faults. If you are tripping a 20 amp breaker this s not unheard of and changing to a 20 amp GFCI device probably won’t change anything as the trip threshold for 15 and 20 amp GFCI’s is the same.

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  • Just to clarify - its the GFCI internal "breaker" thats being tripped. The breaker in the box is fine throughout – Havegooda Nov 23 '20 at 21:58
  • Yes I understand that it is tripping the GFCI device. There is only a measurement of imbalance between the hot and neutral. inductive and. Capacitive loads have opposite effects and large spikes on either lead or lag can end up on the ground and that trips the GFCI , you have to have a O scope to see the effect but it is repeatable. – Ed Beal Nov 24 '20 at 1:17

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