60 Amp or 50 Amp Circuit for Tesla Universal Home Charger???

[ocdxfv]

Thanks. When you power-share off one circuit like that... do the cables daisy-chain? Meaning do you run to one unit, and then "hop" off that unit to the next? How does the basic wiring diagram look? Thanks!

I used something like this. 2 hots (red & black) and a ground (green) go in the top. Then each Tesla was wired to it's own conduit with a red, black & green. I used #6 THHN for hot, and #8 for ground. One unit is set to be the leader (MME), the other is a follower (RAV EV), with the power sharing instructions done through wifi. Even though I'm on a 60 amp circuit, I set mine up to run at 40a max, mostly because my garage gets pretty hot in the summer and at 40 amps max, nothing gets too hot. I also installed a volt/amp meter so that I could verify that the circuit is not being overloaded, which is isn't. When I plug in both cars, they initially charge at 20 amps each, but as one tapers off, the other ramps up. It's a pretty cool system. I can follow the units on the Tesla app. The MME is set (from the car) to charge on non peak hours, but the Rav4 had to be set from the Tesla unit, which was very simple to do.

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[ocdxfv]

My post from a few months ago, with some photos. As is mentioned in the comments, it's probably not to code.

https://www.macheforum.com/site/thr...-using-1-circuit-and-2-wall-connectors.32490/

 

[dvdboulet]

They communicate via WiFi. You connect both to the same circuit.

Yep. I understand that they communicate via wifi. But "how exactly" do they connect to the same circuit? Since you have one breaker and "home run" cable, do you A) take that initial run to one charger, then hop from there to the other? Or do you have to have a separate junction box where the single home-run then splits and runs to each charger?

 

[RickMachE]

Yep. I understand that they communicate via wifi. But "how exactly" do they connect to the same circuit? Since you have one breaker and "home run" cable, do you A) take that initial run to one charger, then hop from there to the other? Or do you have to have a separate junction box where the single home-run then splits and runs to each charger?

All the instructions are online.

The latter.

 

[Jtbuster]

Quote:


“The code is very clear that you cannot install an evse that pulls 48 amps on 6-2. The issue is that that clarity requires looking at several different places in the code book and understanding the difference between maximum over current device and minimum circuit ampacity.





An EVSE is considered a continuous load.



NEC Article 100 defines continuous loads as loads that are expected to run continuously for 3hrs or more .



The minimum circuit ampacity (amount of current wire has to be rated for) is 125 percent of the continuous load, in this case 48*1.25= 60amps



NEC 210.19(A)(1) code reference for that.





Romex cable can only be used at the 60 degree c rating on the NEC ampacity tables.



NEC article 334.80 code reference for that.





Then, we need to look at the NEC ampacity tables. At 60c, #6 (6/2NM cable) is only rated for 55 amps. Commonly, people misapply the round up rule that allows you to round up the over current device (breaker) past the MOCP calculation to the next standard breaker size, which for 55 amps could be 60. However, we are calculating minimum circuit ampacity, not maximum over current protection, so the round up rule does not come to play.



So our options are to use 4/2NM which is rated at 70amps @ 60c (which is impossible to find) or to use #6thhn, which can be rated at 75c as long as the breaker and evse terminals are also rated at 75c (most are) which is rated at 65 amps.



NEC 310.16 reference for that.”

 

[Ghost Ryder]

Quote:


“The code is very clear that you cannot install an evse that pulls 48 amps on 6-2. The issue is that that clarity requires looking at several different places in the code book and understanding the difference between maximum over current device and minimum circuit ampacity.





An EVSE is considered a continuous load.



NEC Article 100 defines continuous loads as loads that are expected to run continuously for 3hrs or more .



The minimum circuit ampacity (amount of current wire has to be rated for) is 125 percent of the continuous load, in this case 48*1.25= 60amps



NEC 210.19(A)(1) code reference for that.





Romex cable can only be used at the 60 degree c rating on the NEC ampacity tables.



NEC article 334.80 code reference for that.





Then, we need to look at the NEC ampacity tables. At 60c, #6 (6/2NM cable) is only rated for 55 amps. Commonly, people misapply the round up rule that allows you to round up the over current device (breaker) past the MOCP calculation to the next standard breaker size, which for 55 amps could be 60. However, we are calculating minimum circuit ampacity, not maximum over current protection, so the round up rule does not come to play.



So our options are to use 4/2NM which is rated at 70amps @ 60c (which is impossible to find) or to use #6thhn, which can be rated at 75c as long as the breaker and evse terminals are also rated at 75c (most are) which is rated at 65 amps.



NEC 310.16 reference for that.”

I'm glad I used 4/3 NM then. But it was not fun to run it.

 

[Space_Pony]

Much appreciated. That definitely "seals the deal" for 60-amp (4 gauge) conduit. Thanks!!!

I hardwired my charger and 6 AWG was the maximum that it would accept. I would ensure that your charger will accept 4 AWG.

 

[Ghost Ryder]

I hardwired my charger and 6 AWG was the maximum that it would accept. I would ensure that your charger will accept 4 AWG.

The Tesla Charger will accept 4 awg. That's what I have.

 

[sukhoi_584th]

I actually have two 200 amp main panels... one has the two AC systems (up and down stairs systems) and various rooms. The other has the kitchen appliances and various rooms (we have a gas stove-top so just the oven is electric). Given the "spread" of items, does one box look like a better candidate to you for powering a new sub-panel in the garage that's dedicated only to EV charging? Thanks!

You're sure they each can pull 200 A? I thought code required a single main breaker on a meter but maybe not.

 

[Maquis]

You're sure they each can pull 200 A? I thought code required a single main breaker on a meter but maybe not.

The NEC allows up to 6 service disconnects as long as they are “grouped”. There are some subtle changes to this in the 2023 NEC, though.

 

[dvdboulet]

You're sure they each can pull 200 A? I thought code required a single main breaker on a meter but maybe not.

Yes. My neighbor who is a certified electrician told me that my scenario is actually called a "400 Amp Panel" even though it's physically split across two individual 200 Amp panels.

 

[dtbaker61]

UPDATE: Based on feedback that I've gotten from a variety of sources, I've absolutely decided to go with a full 60 amp (4 gauge conductor) circuit to drive the hard-wired Tesla wall charger.

NEW QUESTION:

I know that the Tesla so power-sharing... but honestly in the future when we have two EVs (I'm sure this day will come... maybe within the next 5 years) I would ideally like both cars to be able to charge at maximum with two dedicated 60 amp circuits. I'm now thinking of adding a sub panel in the garage that can accommodate 2 such 60 A circuits, and then for now just running off a single 60 A line off that (yet to be) garage sub-panel to my one Tesla charger. My question is what sort of rated Sub-Panel (and conduit to supply it) should I have installed if my end-game is to allow two cars to be able to both charge via 48 amp chargers running continuously at full power at the same time? 125 amp box? Thanks! (p.s. before someone says "ask your local certified electrician" rest assured I will... this is to educate myself before hearing all of the different opinions I'm sure I'll hear when I just that).

Thanks!

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60 Amp or 50 Amp Circuit for Tesla Universal Charger?

I just leased a 2023 GT PE yesterday... coolest thing I've done for myself in decades. The Tesla Universal Charger has been ordered! Should arrive next week.

Question: Should I "plan ahead" and run a true 60-amp circuit (60 amp breaker and 4 gauge 3 conductor wiring) or "cheap out" and just run a 50-amp circuit? The reason I ask is that depending on where I mount my charger... a true 60 amp circuit with 4-gauge conduit is going to cost over $1000 JUST FOR THE WIRE (naturally my electric panel is at the opposite end of the house from the garage and I'm fishing the wire myself to save on labor fees). I know you need a 60 amp circuit for 48 amp charging (which I don't think the ME can actually take full advantage of) and you can limit the charging to also be compatible with a 50 amp circuit. I know I'll be "EV forever" from this point forward and plan to say in my home for at least the next 10 years, so I really want to future-proof as best I can. I just had no idea that copper was this expensive!!!

so.... I love to see people go 'all electric', but hate to see people spend more than they have to.

The first question I would ask is "What do you anticipate your average TOTAL household daily electric miles driven to be after you have 2 electric cars?"

If your answer is less than 200 miles a day.... you really do not need 2 chargers or circuits, and you really don't need to charge at more than 32 amps..... on a 50amp breaker, using 6/3 THHN. Since you say your garage is at opposite side of house, your best bet is pulling wire thru 1" or 1-1/4" EMT, over the roof, or under the soffit if you have a pitched roof.

 

[dtbaker61]

Yes. My neighbor who is a certified electrician told me that my scenario is actually called a "400 Amp Panel" even though it's physically split across two individual 200 Amp panels.

if it is truely 400amp service, you must have a 400amp panel and a single disconnect.... then the 200amp panels are 'sub-panels'? you *should* have an electrician do a load analysis on each to see if you can add a 50a, or 60a, or 2x 60a before you go any further.

 

[Mach-Lee]

Quote:


“The code is very clear that you cannot install an evse that pulls 48 amps on 6-2. The issue is that that clarity requires looking at several different places in the code book and understanding the difference between maximum over current device and minimum circuit ampacity.





An EVSE is considered a continuous load.



NEC Article 100 defines continuous loads as loads that are expected to run continuously for 3hrs or more .



The minimum circuit ampacity (amount of current wire has to be rated for) is 125 percent of the continuous load, in this case 48*1.25= 60amps



NEC 210.19(A)(1) code reference for that.





Romex cable can only be used at the 60 degree c rating on the NEC ampacity tables.



NEC article 334.80 code reference for that.





Then, we need to look at the NEC ampacity tables. At 60c, #6 (6/2NM cable) is only rated for 55 amps. Commonly, people misapply the round up rule that allows you to round up the over current device (breaker) past the MOCP calculation to the next standard breaker size, which for 55 amps could be 60. However, we are calculating minimum circuit ampacity, not maximum over current protection, so the round up rule does not come to play.



So our options are to use 4/2NM which is rated at 70amps @ 60c (which is impossible to find) or to use #6thhn, which can be rated at 75c as long as the breaker and evse terminals are also rated at 75c (most are) which is rated at 65 amps.



NEC 310.16 reference for that.”

Agree with this. #4 romex can be impossible to find, so might as well do #6 in conduit.

 

[kdonnel]

if it is truely 400amp service, you must have a 400amp panel and a single disconnect.... then the 200amp panels are 'sub-panels'? you *should* have an electrician do a load analysis on each to see if you can add a 50a, or 60a, or 2x 60a before you go any further.

I have 400 amp service that was installed as described.

Out by the meter I have 2 200 amp breakers that each feed a panel in the house.

The meter is a Class 320 that has two hole lugs.

That is a typical 400 amp residential service install.

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