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New house, need guidance for at-home charging

I have two issues where I need some advice.

1) 110v charging
There is a 15a circuit in my garage that supports 2 garage door openers and 2 wall outlets, one on each side of the garage. The first outlet is a GFCI and the second is connected to it. When I plug my 5-15 into either outlet, the GFCI trips before charging starts. The breaker in the sub-panel does *not* trip. The house is 3 years old, so the GFCI is relatively new.

I have an electrician at my house today for some other stuff, and he said the wiring on the circuit is not thick enough to support the charger and the excess heat is causing the GFCI to trip. He said it needs to be a 20a circuit and we either need to replace the 15a breaker with 20a and run new wire or add a 20a circuit to the sub-panel and run it out to a separate outlet just for charging.

Clearly you can charge on a 15a circuit, so I question if he has any idea what he's talking about. I would like to be able to charge on 110 immediately until I figure out my 240v situation.

Should I:
A. Replace the GFCI myself to see if that's the issue (remember it's only 3 years old)
B. Keep the 15a breaker and run new wiring to the outlets
C. Replace the 15a breaker with a 20a breaker and run new wiring to the outlets
D. Add a new 20a circuit and wire it to a separate outlet
E. Find a new electrician

2) 240v charging
My main panel is on the opposite side of the house as my garage. I would like to add a 14-50 outlet in my garage, but it's going to require a pretty significant run. My wife will probably get a model Y, so I'd like to deal with that now if we're going to run all the wire.

Should I:
A. Add a single 50a 240v circuit to the main panel and wire it straight to a 14-50 outlet in the garage
B. Add two 50a 240v circuits to the main panel and wire them each to 14-50 outlets in the garage
C. Add a single 100a 240v circuit to the main panel and wire it to a new subpanel in the garage with 2 50a circuits and wire a 14-50 outlet off one of the circuits
D. Add a single 100a 240v circuit to the main panel, wire it to a new subpanel in the garage, and add a HPWC
E. Something else entirely
F. Find a new electrician
 
You can certainly charge on a 15a circuit as I had to do this in a pinch when I first received my S. In fact I was doing it with an extension chord plugged directly into a GFCI outlet. There is 2 things you can try. First I would make sure that the wires are secured into the plug. Its possible that the wires may have come loose a little and that the constant load may be the issue. The other thing you can do is try decreasing the amperage in the car to maybe 10a and see if that still trips the GFCI. The other thing is its possible that the GFCI has gone bad, it does happen.

As for new wiring, since you are planning to get a 2nd Tesla I would wire it up in a way to use a HPWC, if possible wire it up for 2 if you want to have both shared on the same circuit.
 

5_+JqckQttqck

Active Member
Apr 27, 2018
1,851
1,407
Toronto
I have two issues where I need some advice.

1) 110v charging

E. Find a new electrician - What gauge is the wiring on the house? If to code, it should support 15A of current (12A continuous).

2) 240v charging
My main panel is on the opposite side of the house as my garage. I would like to add a 14-50 outlet in my garage, but it's going to require a pretty significant run. My wife will probably get a model Y, so I'd like to deal with that now if we're going to run all the wire.

Should I:

A. Add a single 50a 240v circuit to the main panel and wire it straight to a 14-50 outlet in the garage = Most cost effective/short term.

D. Add a single 100a 240v circuit to the main panel, wire it to a new subpanel in the garage, and add a (2)HPWC = $.$/long term proofing Model Y (If the Model Y can only charge at the same 48A... 100A is a bit of a overkill).

O. Other: I would do a 60A 240V circuit on the main > Garage Sub with 60A breaker > 2x HPWC daisy chained. Both cars plugged in, they'll share 24A each (more than enough for daily commute). 48A will allow for max charge rate for 1 vehicle at a time.

It will be rare that both cars need 48A and plugged in at the same time. Unless you road trip with both driving... which I can see as both persons want to drive their Tesla haha.

100A cable vs 60A cable = mucho dinero.
 
Last edited:
If it were me, I would go with option D under the 240 options. I use my garage alot, so adding capacity with a sub-panel would be good. That's just me though.

We need some additional information to be helpful.

1. What is your commute like? Your wife's?
2. Do you like the idea of starting with a full charge in both cars each morning?

Depending on your answers, I would lean to running two 50amp circuits with two 14-50 plugs. That is a good balance between cost and capability. The cost to run 1 wire and 1 outlet will not be much less than 2 wires and 2 outlets. For the P3D and LR, you should get 29-30 miles of charge per hour using the 14-50 plug and 50 amp circuit.
 
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Rockster

Active Member
Oct 22, 2013
3,025
4,710
McKinney, TX
If your panel had the capacity to handle the load, I'd go all out and run a single 100 amp circuit to the garage and install two wall connectors to share that single circuit. You then have the more convenient charging solution than dealing with the mobile connector and 14-50 outlets and you're ready for your second Tesla. Yes, it's more pricey but it's a more robust and more attractive permanent solution.

Compared to the cost of two Teslas, paying extra to have a charging setup that's rock solid like this would be is worth the cost, IMO.
 

jmaddr

Active Member
Mar 29, 2019
1,201
1,199
Florida
Forget about 120V. But if you want to know if the electrician knows what he's talking about I would say he's missing something b/c he doesn't know much about mobile charger. The mobile charger has built in GFCI and "daisy-chaining" GFCIs is problematic. It can work if wired correctly, but it also cause stupid problems like these. The downstream GFCI may perform an internal self-test when energized (I don't really know if the Tesla mobile charger does this but it would explain your situation), which the upstream GFCI (your outlet) detects as a fault.

But even if you can get it to work, forget about paying someone to get ~5 miles of charge per hour, it's just not worth it. Have them send 240V like stated above or get the HPWC. Hopefully you have the breaker space and amp capacity to support. If you don't, there are a few tricks like replacing two breaker with multi-port single width breakers and setting charging schedules only during non-peak times like at night. Neither of these are ideal and cause their own "nuances" so hopefully you have the space and amp capacity.
 
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O. Other: I would do a 60A 240V circuit on the main > Garage Sub with 60A breaker > 2x HPWC daisy chained. Both cars plugged in, they'll share 24A each (more than enough for daily commute). 48A will allow for max charge rate for 1 vehicle at a time.

It will be rare that both cars need 48A and plugged in at the same time. Unless you road trip with both driving... which I can see as both persons want to drive their Tesla haha.

100A cable vs 60A cable = mucho dinero.

This right here.
 
1F) In a pinch, get a heavy duty 15a extension cord to a circuit that works for you. Also consider connecting to a dryer circuit with an extension cord. Otherwise, I would play the long game and add a sub-panel in the garage.

2C variant) Add a 60A or 100A sub panel in the garage. Get quotes for either option. If lucky, you may find the cost difference is not too much. After that, there is flexibility what outlets are used.

If it was me, I would do the 2x HPWC daisy chained with a 14-50 and 5-20 outlets. At least have the 14-50 for the flexibility of guest charging or if you switch to a different car.
 
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I personally went with option D. My garage is pretty large and the builders completely skimped on power out there.

I put a load center (sub panel not really the right word) in the garage using 1/0 SER cable from my basement. Had about $250 in wire.
My garage is 3 car, and had 1 15-amp receptacle that is shared with our living room, and 2 20-amp receptacles that are on their own circuit for the garage openers, but they're a pain to get to on the ceiling.

I had a 100 ft run from the 200amp main. It's so nice to have dedicated power out there now!

All of that being said, you need to make sure you have enough load capacity to do a 100amp load center in the garage. Even a 60 or 80amp service with shared HPWC would be awesome. With them load balancing automatically how often are you going to need to charge both cars at the same time at full amperage?

Wire used:
WIRE SER 1/0-1/0-1/0-2 ALUM 1000R

Size calculator:
Wire Size Calculator
 
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Thanks everyone. This is really helpful. Was able to get the name of a competent electrician from a neighbor with a MX and speak with him on the phone. He’s coming out Monday morning to estimate the work.

Based on our call, I think I’ll add a 60a circuit on the main panel and wire it straight to a 14-50 outlet. If and when my wife gets a Y and we both need to charge at the same time, I will remove the outlet and daisy chain two HPWCs. Electrician thought a sub panel was a needless expense.

Sounds like I can charge at 110 until then by replacing the garage GFI outlet with one that is not protected. However he said at that point I’m in violation of code and would have an insurance issue if anything were to happen. Is that likely? Seems like a pretty simple fix to keep the car topped off and keep me from having to visit the SC, which is often full.
 
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Sounds like I can charge at 110 until then by replacing the garage GFI outlet with one that is not protected. However he said at that point I’m in violation of code and would have an insurance issue if anything were to happen. Is that likely? Seems like a pretty simple fix to keep the car topped off and keep me from having to visit the SC, which is often full.
Well, he's right that you'd have an insurance issue if something were to happen while violating code. And, charging an EV on a 120 (they're not 110 anymore) does increase the risk of fire. Interestingly, that's not what the code you're violating is meant to prevent, but I don't think the insurance would care about that subtlety. The risk is from the heat, and the fact that even though rated for 15A and therefore 12A continuous, it's not the expected use for such a circuit, and it may not actually be able to handle it. If you go that route (and even if you get the GFCI to work and you're charging on that with no code violation) you want to make sure the outlet is of high quality, all the wiring is in good shape, and monitor for heat build-up. That's the way my garage was wired when I got my first EV (no GFCI, not even grounded properly), and I did charge that way until getting it all upgraded, but it always made me nervous.
 
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brkaus

Well-Known Member
Jul 8, 2014
8,647
7,267
Austin, TX
Sounds like I can charge at 110 until then by replacing the garage GFI outlet with one that is not protected. However he said at that point I’m in violation of code and would have an insurance issue if anything were to happen. Is that likely? Seems like a pretty simple fix to keep the car topped off and keep me from having to visit the SC, which is often full.

I would buy a new gfci and try that first. Pickup a good quality regular outlet just in case.

Edit - you can also try setting the current lower in the car. Won’t charge as fast, but will reduce the heating of the circuit. Of course reducing very slow to.. may not be much use.
 
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Nocturnal

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Supporting Member
Aug 23, 2018
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It's probably a bad GFI outlet. I had no problems with mine tripping on a 15 amp circuit. I'd try replacing the outlet in the short term.

If you are going to be a two EV house then you definitely want to go ahead and install the 100amp circuit. Running new wring to the 15amp outlets doesn't make sense, waste of money.
 
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If Tesla had better SC coverage in Nashville it would be less of an issue. The one SC in town is down in the burbs and has 6 spots that are often all in use. Even if 1 is open, charge rates are horribly slow until the adjacent car is close to finished. It’s a huge PITA unless you go at 11pm when it’s empty :)

I’ll buy a new GFCI and see if replacing it helps until 240v work is done.
 

Nocturnal

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Aug 23, 2018
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Deepening Crisis!
If Tesla had better SC coverage in Nashville it would be less of an issue. The one SC in town is down in the burbs and has 6 spots that are often all in use. Even if 1 is open, charge rates are horribly slow until the adjacent car is close to finished. It’s a huge PITA unless you go at 11pm when it’s empty :)

I’ll buy a new GFCI and see if replacing it helps until 240v work is done.
Hopefully there are some in the works. Here in KC we didn't have new ones in a year or so and then suddenly several new ones a few months back.
 

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