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

[That Beast Mode]

Whatever the breaker or wire is rated at you can only use 80% of that, and you have to drop to the next level down. If Romex is rated at 57 amps max, then the next level down is 48, and 80% of that is more like 40 amps. Can an electrician say whether this is correct? As I mentioned earlier, my understanding is that Romex is for household appliances and not for constant high-amperage draw.

Correct, I am running it at 40A charge.. to answer your question on about the household appliance thing that's above my pay grade, I'll wait for someone else to chime in

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[That Beast Mode]

then I would stay with the 50 amp, fires are devastating
slow charge is better for battery life
manage the charging in the app, like i do
i home charge with two 2024 FS Cyberbeasts, currently one charger, TESLA ABC's always be charging!
I just ordered two New Gen 3 wall charges to connect with my power share,
my plan is to install two power share units, and two wall chargers for two cyberbeasts, I do have a
6043 Sq foot home in Georga, that has two GE Panels,
next year ill start my installation, first without solar, see what efficiencies I can produce, I do have Free Lifetime supercharging, on One Beast,
if I do not get a lower electric bill, Ill add solar panels,
I currently Charge at My home in Connecticut, with Solar, so I always have one truck charging in the day light.
I am considering adding a second charging cord, like your adding, but i am weighing the cost. I'll be moving permentaly to GA in 2027 so moving the cord from truck to truck is fine

Your set up sounds a lot more serious than mine. Lol. I'm just tired of playing musical charging cords.

 

[CyberGus]

If the Wall box can talk to each other and Limit your total draw on the circuit, but you are still taking a chance if that system ever fails and both are on at the same time.

Id rather it do power management like others suggested and if there was a flaw in the system and they both turn on at full blast for some reason then trip the 50A breaker.

Once the WC's are properly configured for Group Power Management, a communication failure will result in a drop to Safe Mode of only 6A. It's not possible to overload the circuit.

 

[Jimo]

Both vehicles will try to pull 48a and trip the breaker, run a second set of wires for safety and convenience.

Your electrician should recommend a second complete circuit with its own breaker. Hopefully you won't have to upgrade service for your home to accomodate the extra amperage draw.

 

[eswimm]

Lots of presumably well meaning, but nonetheless wrong information in this thread. I would recommend ignoring us all and finding a knowledgeable, licensed electrician. You can also review the official Tesla One installation videos to inform yourself and increase confidence that your electrician knows what they're talking about. Some of the advice in this thread is wrong and/or dangerous.

 

[comet2]

I have a question about adding a second charger that maybe some of you might know the answer to for me - and before you jump on me, I am not planning on doing this myself, I'll have a licensed electrician confirm and do the work, I just don't want to sound stupid when I am discussing what I want with them.

I have Romex wire in my garage on a 50A breaker currently for my Tesla wall charger. I want to install a second wall charger outside the garage. Can the electrician tap off the existing wires to run a line for the second charger? I want to be able to plug both cars in at the same time - I don't think they would be able to both charge at the same time and that's fine with me.

If this is possible, do the Tesla chargers handle which one gets charged? Does it half and split the power and charge both with this method? I don't want to overload the wires obviously. The install is way easier than getting another run installed from the breaker in the basement to the garage. I know the better way is to have dedicated lines to the panel for both chargers so they can run at full capacity when needed, but I never have a circumstance where I need to charge both at the same time. It's always one or the other but I'd like to not keep having play musical chargers and just add a second one. Thanks.

https://getneocharge.com/products/neocharge-smart-splitter?variant=41833619325123

see if this helps. I was recently researching this exact situation and came across this. Did not get a 2nd Tesla so didn’t need this.

 

[Jhodgesatmb]

Lots of presumably well meaning, but nonetheless wrong information in this thread. I would recommend ignoring us all and finding a knowledgeable, licensed electrician. You can also review the official Tesla One installation videos to inform yourself and increase confidence that your electrician knows what they're talking about. Some of the advice in this thread is wrong and/or dangerous.

Agreed. But this is from the manual:

https://digitalassets.tesla.com/tes.../gen-3-wall-connector-installation-manual.pdf

Branch Circuit Conductors and Ground Wire

• If installing for less than maximum power, refer to local electrical code to select correct
conductors and ground wire size that are suitable for the chosen circuit breaker.

For maximum power, check temperature rating of circuit breaker used:

For 60°C rated circuit breaker, use minimum 4AWG, 90°C THWN-2-rated copper wire for conductors.

For 75°C rated circuit breaker, use minimum 6AWG, 90°C THWN-2-rated copper wire for conductors.

• For sites with multiple Wall Connectors, the power sharing feature can enable the safe utilization of a single branch circuit. See single line examples in Breaker and Branch Circuit Setup on page 33.

• COPPER WIRE TERMINATIONS ONLY for landing in Wall Connector wirebox terminals. Conductors can be stranded or solid. • Hardwire branch circuits to disconnects or circuit breakers. Do NOT install cord-and-plug type connections.

• For outdoor installations, use watertight fittings when securing feeder wires to the wirebox.

 

[mongo]

Agreed. But this is from the manual:

https://digitalassets.tesla.com/tes.../gen-3-wall-connector-installation-manual.pdf

Branch Circuit Conductors and Ground Wire

• If installing for less than maximum power, refer to local electrical code to select correct
conductors and ground wire size that are suitable for the chosen circuit breaker.

For maximum power, check temperature rating of circuit breaker used:

For 60°C rated circuit breaker, use minimum 4AWG, 90°C THWN-2-rated copper wire for conductors.

For 75°C rated circuit breaker, use minimum 6AWG, 90°C THWN-2-rated copper wire for conductors.

• For sites with multiple Wall Connectors, the power sharing feature can enable the safe utilization of a single branch circuit. See single line examples in Breaker and Branch Circuit Setup on page 33.

• COPPER WIRE TERMINATIONS ONLY for landing in Wall Connector wirebox terminals. Conductors can be stranded or solid. • Hardwire branch circuits to disconnects or circuit breakers. Do NOT install cord-and-plug type connections.

• For outdoor installations, use watertight fittings when securing feeder wires to the wirebox.

Yah, and NM-B (aka Romex) is rated at the 60°C value while its individual conductors are 90°C rated. It is fine for Wall connectors when properly sized.

https://encorewire-prod.imgix.net/m...opper/residential/EncoreWire_NM-B_11.2024.pdf

 

[rjmcinnis]

Your set up sounds a lot more serious than mine. Lol. I'm just tired of playing musical charging cords.

I literally just did this yesterday. I'm not comfortable working in a power panel, but plenty comfortable working at the end of a breakered circuit.

First off, Romex 6/2 is rated for 55a at 60 Celsius. As you know, you have to use it on a 50a breaker, and set your WC for 40a to meet the 80% continuous rule.

Backstory: When I built my house, they had an option for a 14-50 Nema for EV, which I selected. They would NOT leave it unterminated in a box, so I had to get the connector. I SPECIFICALLY requested in writing that they NOT use ROMEX, and use #6 THHN instead, so I could use it to hardwire the WC and use 48a (after switching out the breaker to 60a). Naturally when I took possession, it was 6/2 Romex lol. So much for" best laid plans".

So I had an electrician come in and run a new 60a breaker and #6 THHN right next to the plug, and install my UWC. Worked great for the last 2 years for my M3P. Just bought a Cyberbeast last month, and knew it would be a PITA to switch cables between, so decided to add another UWC on the other wall, which I did yesterday.

I ran S40 PVC conduit and 2 #6 THHN, as well as 1 #10 THHN for the ground. It's super easy to physically add the new wires. I routed from the bottom (original to the breaker came from top), up and over the garage, and down into the second UWC. Gee, thanks...

Here is where it gets interesting/frustrating. I, like many here probably, am a perfectionist. It took me 6 hours to do what an electrician would probably do in 1-2.

But when I opened the original box, I immediately noticed he routed the wire directly into the top lugs, instead of down/around to the bottom as shown in the instructions. And no extra wire to change it myself.

Then, I went to tighten the wires to the correct torque specs. I know that's important, and had that reinforced from the thread here with the fire. I torqued mine to 50 in/lbs. "Hey, let me check the -certified electrician's- lugs... 20-25 in/lbs... WTF?" Now I want to have the other end in the panel checked, as I don't trust they are torqued right either.

Setting up the Group Share is easy as long as you kept the paper with the codes from your WC. Just log in using the Tesla One app, and follow the instructions. Basic setup of the Leader, then basic setup of the Follower. Then back to the Leader page, Set the Max for the breaker, add the Follower to the Group, Enable Group Share (Has to be disabled for changes). Easy peasy.

Sorry for the long diatribe, my point is most electricians just honestly aren't going to care about your house nearly as much as you do.

 

[eswimm]

Agreed. But this is from the manual:

https://digitalassets.tesla.com/tes.../gen-3-wall-connector-installation-manual.pdf

Branch Circuit Conductors and Ground Wire

• If installing for less than maximum power, refer to local electrical code to select correct
conductors and ground wire size that are suitable for the chosen circuit breaker.

For maximum power, check temperature rating of circuit breaker used:

For 60°C rated circuit breaker, use minimum 4AWG, 90°C THWN-2-rated copper wire for conductors.

For 75°C rated circuit breaker, use minimum 6AWG, 90°C THWN-2-rated copper wire for conductors.

• For sites with multiple Wall Connectors, the power sharing feature can enable the safe utilization of a single branch circuit. See single line examples in Breaker and Branch Circuit Setup on page 33.

• COPPER WIRE TERMINATIONS ONLY for landing in Wall Connector wirebox terminals. Conductors can be stranded or solid. • Hardwire branch circuits to disconnects or circuit breakers. Do NOT install cord-and-plug type connections.

• For outdoor installations, use watertight fittings when securing feeder wires to the wirebox.

None of that is wrong, although Romex is allowable, especially because THHN or THWN aren't rated for in-wall usage without conduit. Romex has different temperature requirements however and therefore lower current capacities. It's why the OP is charging at 40A on 6/2 Romex, because it isn't rated for the 60A required to charge at 48A. One of my wall connectors uses 3/2 Aluminum wire from the panel to a disconnect right before the wall connector and 6 AWG THHN copper for the couple feet between the disconnect and the wall connector. The disconnect allows for much cheaper Aluminum wire (even though it has to be 3 AWG for the current) for 70' of the run and then a short run of also cheap 6 AWG THHN in conduit for the 4-5 exposed feet at the end. All Aluminum isn't an option because the wall connector isn't rated for Al conductors and all copper would have doubled the wiring costs without simplifying the job. It would have still needed to transition wire types since you can't run THHN without conduit and Romex has stricter conduit requirements.

 

[The Duke]

Both vehicles will try to pull 48a and trip the breaker, run a second set of wires for safety and convenience.

Incorrect. The chargers can be set to split available power. They talk to each other. Alone, one will pull full amps, together they will pull half amps.

Of course you have to know what you are doing to set this up. Not hard at all. I set up mine by getting the info online.

50 amp breaker wired to junction box (50 ft away) that splits into the two chargers. One car charges at 50 amps when needed, two cars charge at 25 amps.

 

[The Duke]

Your electrician should recommend a second complete circuit with its own breaker. Hopefully you won't have to upgrade service for your home to accomodate the extra amperage draw.

He may or may not. If you don't need to charge both at once there is no need to run the extra wire.
And even if you do charge both at once, you probably don't need to charge both at max amps.

 

[Jimo]

He may or may not. If you don't need to charge both at once there is no need to run the extra wire.
And even if you do charge both at once, you probably don't need to charge both at max amps.

I'm not certain of the electrical code; but I believe it's like double-tapping a breaker. Ideally you could use one charger at a time BUT that ONE TIME you used both simultaneously would trip the breaker.

 

[Jimo]

No and No and No
1. The is continous amp draw and that is a 80% rule or 48amp/.80=60 amps
2. Wire for 60 amps
3. Plug must be 60 amps
4. Torque wire screw and hold for 5sec and re torque and re held.
and
You can not series wire amps.
Correction
You can series wire amps but you must double the amp desing.
and
That was your original question can I series wire an EV charge circuit and use the existing wires and plugs (which what you have is no per code and could cause fire)
Be Safe
Put in one of those 5 year battery operated smoke detector in your charge area.

Just being a little nit-picky, but I think he wanted to wire it in parallel. Series would be a whole different animal

 

[Ivessm]

1. Wiring should not be Romex. Should be 6/2 MC.
2. Breaker should be 60 amp double pole to adhere to 80% limitation on constant draw circuits 80% of 60 amp = 48 amp max draw
3. DO NOT use receptacles. Hard write only.
4. Torque ALL lug points to spec and recheck.
5. READ THE DIRECTIONS!

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