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Tesla Wall charger on a "50 amp circuit"

Electrician installed Gen 3 wall connector and puts 60A breaker.
Can i charge Tesla 3 Standard Range which is only used 7.7 kW or 32-amp?
Of course. EVSE will advertise 48A, but the car will only take 32A. They negotiate based on the capabilities of both and whichever value is lower is what actually gets delivered.
 
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If Car takes 32A, meaning will use less electricity to charge it?
Depends what you call electricity. It will use less current (32 Amps instead of 48 Amps) but that also means you have to charge longer. The amount of energy you put into the battery is the same, so charging slower isn't going to save you any money if that was your question.
 

Sophias_dad

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Jul 29, 2018
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Depends what you call electricity. It will use less current (32 Amps instead of 48 Amps) but that also means you have to charge longer. The amount of energy you put into the battery is the same, so charging slower isn't going to save you any money if that was your question.
I had interpreted the question as "is that extra 16 amps going to be thrown away, tremendously increasing my recharge cost with no benefit".
 
The current setting in the wall connector is what the charger will tell the car it can deliver. The car will draw what it wants up to that limit or below. Level 1/2 chargers are fundamentally very dumb devices. Their main job is just to tell that car what it can draw from the connection and turn the power on and off, but the actual AC power is just passed straight through to the car. Some obviously come with extra bells and whistles like time of use stuff or billing, but those are extra functionality.
 

appleguru

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Mar 15, 2017
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This is misleading because the termination points have to be considered. You can probably read from the 75C column of Table 310.16 in the NEC.
Indeed.. I did say “up to” didn’t I? ;-) But yes, since most residential breakers have 75c rated terminals, you’d be limited to the 75c column, so 65A in this case for #6. But you still get to derate from the 90c column (75A), eg for thermals!

The risks here are two-fold: 1, that the breaker trips one too many times and then does not work as intended. Or 2, that the breaker does not trip and the conductors over-heat at the termination points.

Sure, but 1) if the breaker is tripping, OP would know and 2) since the conductors are properly sized (based on the limited information we have here), overheating should not be a concern.

Is the #6 AWG THWN2 enough for 48 Amp draw ? It depends on corrections and adjustments, like maximum ambient temperature. E.g. the 75 max Amps of TWHN2 can be derated 20% and still carry the 48 Amp EV load. An ambient max temp over 122F would require a larger size conductor.
Obviously an electrician familiar with the actual install should evaluate and do the calcs, but real world #6 THWN-2 in conduit is sufficient for a 48A code compliant install 99% of the time.

625.41 is pretty clear that the breaker should be 60A for a 48A EVSE install though, but I still contend that using a lower current breaker is not a safety issue unless you are trying to land a wire improperly sized for the breaker on it.
 

Rocky_H

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Feb 19, 2015
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@dho112 I just got through reading all of the replies, but the topic of this thread is based entirely on your misunderstanding of the issue and what Sandy Munro was warning about. It has nothing to do with the amp rating of the circuit, whether it's 60A or 50A. The real issue that is kind of a safety concern is with things being either hard wired, or using a plug cord into an outlet. That can be a very big deal with the common cheap garbage-quality outlets that are used too often and can really be a bad idea.

From reading about your installation, it sounds like you have wire in conduit, directly hard wired into a wall connector. It is sufficient wire gauge for either a 50 or 60A circuit. Either is just as safe, and there's nothing wrong or less safe with having it set up as a 50A circuit.
 
I read several threads where people were asking about connecting their Tesla Wall Chargers onto an existing 50 amp circuits in their electrical panel. I believe most of these were talking about utilizing existing 14-50 electrical dryer circuits for their Wall Chargers installs.

I was watching a recent Sandy Munro video where he was talking about (warning about) people who connect using the wiring and breaker to this circuit (48 amps wall charger) Warning that these residential circuits are not meant for a continuous 50 amp load and are intended for partial duty loads as you would see with an electric dryer, which is not going to run continually at full load for hours and hours on end perhaps every single day. He showed samples of melted connectors, torched wiring from people who had installed their wall chargers this way and were charging every day etc... He talked about how you need to have 60amp circuit for a Wall Charger and use good components meant for continuous duty.

I just had a dedicated circuit installed for my Model 3 Performance by an electrician (before I saw the Munro video), and I remember the installer saying that the 50 amp circuit they were installing was more than fine for my charger. Especially since he used a double 50amp breaker that I supplied that he said worked fine in my Eaton electrical panel. He actually said it was overkill. It is a Siemens unit and cost me over $100 (I just asked the guy at the counter (what's the best one you have?) :)

But I was worried because Mr Munro said the circuit is supposed to be designed for a certain percentage in AMPS above what you're sending thru it. I can't remember what that percentage was.

Worried, I looked at my invoice for the work that was done, and the wiring length is 23' of "#6 THWN-2 in flex metal conduit" and with my 50amp Siemens breaker and Tesla Wall Charger listed as customer provided.

My understanding is that the Wall Charger pulls 48amps max. Is the fact I have a "only" 50 amp breaker installed bad? Doesn't that mean that it will trip at 50+ rather than 60+ if I had that sized breaker installed? I looked up THWN-2 #6 wire and it said it is rated for 190 C and 75amps so am I good to go the way I have it set up? Or is there something I'm not considering (not an electrician here)

Thanks in Advance!
Your #6 Wiring is actually rated for 65 amps as we cannot use the 90 degree rating unless the equipment is specifically rated for 90 degree terminations, which is very rare. Anyway.. that wiring could be terminated on a 60 amp breaker which would allow 48 amps of continuous current to flow through before tripping.

You may be fine using the 50 amp breaker and never have issues with it tripping, however I would recommend having the 50 changed for a 60 to avoid the possibility. That being said, if the wiring installed was connected to a 14-50R Receptacle, the maximum sized breaker allowed would be a 50.

You also shouldn't be using a Siemens breaker in an Eaton Panel, especially for such a high power application Siemens breakers are not approved for use in Eaton panels and vice versa. Over time, there could be arcing and melting of components in your panel. I've seen this before.

Big lesson is find someone qualified, who has experience with the particular job and have them supply and install everything. That way, if something fails, it's on them to warranty.
 
Wow! Thank you all for the great, informative replies. So much to learn it's good to have info. I know I can overanalyze things FAR too much, too often. The wife says it's a Virgo thing LoL!

I ended up calling the electrician company that did my install, and they confirmed that the install was correct, and I re-confirmed that they were both licensed and bonded in California, and the install had actually been signed off on by a city building inspector (which I didn't know happened actually on the very same day as the install!) I missed that, because he came and went very quickly near the end of the install.

So I'm going to call it good and focus my attention on getting another set of wheels for the Tesla LoL!
 

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