Adding a 2nd Tesla home charger and tapping the wires.

[rjmcinnis]

240.4
(B) Overcurrent Devices Rated 800 Amperes or Less.
The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:
(1) The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads.
(2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjust‐
ments).
(3) The next higher standard rating selected does not exceed 800 amperes

(1) is satisfied since the circuit is not feeding outlets
(2) is satisfied since 55A does not correspond to a standard breaker that lacks adjustment.
(3) is satisfied since 60A is less than 800A

So a 60A breaker on 6 gauge NM-B is code compliant.

You just left out the entire last line of the 2023 NEC, but that's ok, you do you bro. I'll stick with what's approved in Florida, and avoid the unnecessary risk of fire, which won't be covered by insurance here if it did happen.

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[mongo]

You just left out the entire last line of the 2023 NEC, but that's ok, you do you bro. I'll stick with what's approved in Florida, and avoid the unnecessary risk of fire, which won't be covered by insurance here if it did happen.

All I had to reference is a 2017 version and that was the complete subpart, please post this line of which you speak.
If someone doesn't have a 51-55A load (41-44 continuous) there is no real benefit to the 60A breaker, but that doesn't mean it's not code compliant (at least in the old version) which has been the point of contention.
Of course local code can be more restrictive, but being non-approved in one jurisdiction does not make it unapproved or non-NEC elsewhere.

As to fire risk, a 40A (6 ohm, 9600W) fault can start a fire on a 50A breaker just as easily as a 60A breaker.

 

[FL370]

Lots of opinions here. I faced the same question a couple of years ago, and despite my efforts to engineer a solution with one breaker feeding two Tesla chargers, I ultimately ran a separate 50-amp breaker and wire to the second charger. I then upgraded the first Tesla charger to the Universal Wall Charger 60 AMP breaker to the Powershare. We typically charge after midnight, when other electrical demands are generally very low.

A 50 AMP breaker and this wire https://www.amazon.com/dp/B08R5QW8SC?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_6&th=1 all totaled, less than $300 - well worth the peace of mind.

 

[That Beast Mode]

You don't set the car to 44AMPS (I think you can do that but that is not what you want). You set the max powershare amount to 44AMPS which then only allows the sum of all wall connectors to pull 44AMPS total.....I have 3 wall connectors setup this way such that they can pull either 14amps each, 22Amps each or 44Amps depending on how many cars are charging at once.
This is done through the URL on your smartphone or ipad when connected to the WIFI network for the master wall connector

Ah that explains why I can't do it. I don't have the second charger or power share for it installed yet. Just the one charger.

 

[mongo]

Ah that explains why I can't do it. I don't have the second charger or power share for it installed yet. Just the one charger.

I think they meant group power management, not Cybertruck Powershare. Might be able to set it up without any followers...

See page 29 (UMC version),Tesla One app accepts your regular Tesla username & password
https://digitalassets.tesla.com/tes...-Wall-Connector-Installation-Manual-NA-EN.pdf

 

[JerseyMike]

You are basing your calculation on 6/2 Romex being rated for 55a. However, 6/2 Romex should be on a 50a Breaker, NOT 60a. So you should base your calculation on 50a x .8 = 40a continuous load.

I think they meant group power management, not Cybertruck Powershare. Might be able to set it up without any followers...

See page 29 (UMC version),Tesla One app accepts your regular Tesla username & password
https://digitalassets.tesla.com/tes...-Wall-Connector-Installation-Manual-NA-EN.pdf

Sorry, I may be using the wrong term with power share. I think they used to call it power sharing in the manual

 

[That Beast Mode]

I think they meant group power management, not Cybertruck Powershare. Might be able to set it up without any followers...

See page 29 (UMC version),Tesla One app accepts your regular Tesla username & password
https://digitalassets.tesla.com/tes...-Wall-Connector-Installation-Manual-NA-EN.pdf

Awesome, thanks. Honestly, I don't really need to change anything just yet anyway until I get the 2nd charger installed. My setup is fine for me now, I just don't want to deal with dragging cables around all the time.

 

[That Beast Mode]

Sorry, I may be using the wrong term with power share. I think they used to call it power sharing in the manual

Lol, I don't have either one set up anyway so it's all good.

 

[mongo]

Awesome, thanks. Honestly, I don't really need to change anything just yet anyway until I get the 2nd charger installed. My setup is fine for me now, I just don't want to deal with dragging cables around all the time.

It would be interesting to know if you can set Group Power limits with only one wall connector though

 

[That Beast Mode]

It would be interesting to know if you can set Group Power limits with only one wall connector though

I can try if you want, but id need a little assistance to guide me on how id do that.

 

[mongo]

You just left out the entire last line of the 2023 NEC, but that's ok, you do you bro. I'll stick with what's approved in Florida, and avoid the unnecessary risk of fire, which won't be covered by insurance here if it did happen.

AFAICT, the only change to that section in 2023 was clarification that when using adjustable breakers, you can set it to the next higher level if the ampacity doesn't match a standard value. Does the Florida Electrical Code have something additional ?
From https://www.electricalassociation.com/common/Uploaded files/PowerPoints/PowerPoint 2023 NEC Code Update Part 2.pdf

 

[rjmcinnis]

It would be interesting to know if you can set Group Power limits with only one wall connector though

You cannot. You have to have a Leader, and at least one Follower configured on the same network before the Group Power button can be utilized. After that, each time you want to change something, you have to disable it first. It's really not very user friendly honestly.

 

[rjmcinnis]

AFAICT, the only change to that section in 2023 was clarification that when using adjustable breakers, you can set it to the next higher level if the ampacity doesn't match a standard value. Does the Florida Electrical Code have something additional ?
From https://www.electricalassociation.com/common/Uploaded files/PowerPoints/PowerPoint 2023 NEC Code Update Part 2.pdf

Yes, that was the line I was referring to. Other than that, I only know what I was told by my installer, that it wouldn't pass inspection here in florida. So I read up on it to better understand the issue.

Seems to be to be a gray area, with people on both sides adamant that 6/2 romex can, or cannot be on a 60a standard circuit breaker. A quick google search will see this discussion in nearly any EV forum you can think of. With examples of it passing inspection, and others where it doesn't.

Considering that most inquiries about 6/2 on a 60a circuit didn't involve an EV, I can certainly see why those saying it's dangerous for a continuous load like EV charging make that interpretation.

I personally didn't see it being worth the risk vs just having a new line ran so I could use 48a vs 40a, without worrying that a fire wouldn't be covered.

I do wonder if since the ratings are based on heat dissipation, perhaps it's more strict in states like Florida, vs Michigan where you live? The ambient temp in my attic is significantly hotter than ones I've been in in cooler states.

 

[mongo]

Yes, that was the line I was referring to. Other than that, I only know what I was told by my installer, that it wouldn't pass inspection here in florida. So I read up on it to better understand the issue.

Seems to be to be a gray area, with people on both sides adamant that 6/2 romex can, or cannot be on a 60a standard circuit breaker. A quick google search will see this discussion in nearly any EV forum you can think of. With examples of it passing inspection, and others where it doesn't.

Considering that most inquiries about 6/2 on a 60a circuit didn't involve an EV, I can certainly see why those saying it's dangerous for a continuous load like EV charging make that interpretation.

I personally didn't see it being worth the risk vs just having a new line ran so I could use 48a vs 40a, without worrying that a fire wouldn't be covered.

I do wonder if since the ratings are based on heat dissipation, perhaps it's more strict in states like Florida, vs Michigan where you live? The ambient temp in my attic is significantly hotter than ones I've been in in cooler states.

Yeah, I think there are two separate issues.
Under NEC:
One can put a 60A breaker on #6 NM-B
One cannot recalculate the load capacity based on the upsized breaker.

So
One cannot run a 48A charger off of #6 NM-B
But
One can put a 60A breaker on #6 and have a Wall Connector set to 40A charging, which is 50A calculated, which is lower than the 55A rating. Not that the extra 10A of breaker has any benefits.

My point was that the breaker size is not illegal so as to avoid people getting in conflict with installers.

There are ampacity adjustments for the environment (and multiple current carrying conductors in a raceway). Hot attic vs conditioned space, but I think NM-B starts at the 90C value, and gets derated from there. Ideally, the house construction (vented on insulated attic) makes it a non-factor.

 

[DMSTR]

I'm late to this conversation but want to share a quick note in case anyone finds themselves here after searching (as I did). I have two Gen 3 wall chargers. Neither is a UWC (Universal) and both are wired separately with #6 and 60amp breakers. I struggled with setting up the Group Power Management until I realized the app I was directed to use was not the Tesla app currently on my phone (as I ep thinking it was).

I found directions to login to the Tesla One app but couldn't understand why I didn't see what I was being told I should see within the app. The Tesla One app is a blue icon. For me (Android) it can be found in the Play Store. My login was the same as with my red Tesla app and once logged in, found the Group Power Management option under Device Settings.

The Gen 3 wall charger with the help of the Tesla One app, can be told to share a maximum available amperage so as not to overload an existing panel. The two chargers are not physically connected in any way. The two chargers communicate over Wi-Fi (their own SSID not yours). The programmed amp maximum is split among the two chargers (supports up to 6 chargers I believe) and provides the full amount to a single charger if no others are in use. Of course you can still reduce the amps for a single vehicle without accessing the setup. Just make that adjustment in the "red" Tesla app. Hope this helps some one.

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