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Tesla Wall charger on a "50 amp 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!
 

Sophias_dad

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The 50 amp breaker you got was most likely a GFCI breaker, it is expressly not-allowed per the HPWC manual.

You would actually be allowed to use a 60 amp breaker with the wire that's installed. It won't hurt anything to run it at 50 amps(40 delivered) though. You could have saved ~$75 and gotten 20% faster charging by going to home depot and getting the correct breaker.

There's supposed to be a 25% overhead for an EV circuit in the wires/breakers, so a 50 amp breaker and wire can supply 40 amps continously.

For the #6 TWWN-2 you are actually limited to 75C ratings, since the ends (the HPWC and breaker) are only rated to 75C. This means 65 amps, and is still plenty to drive the 48 amp maximum on a HPWC.
 
There are literally dozens if not hundreds of threads about charging, wall connectors, wire sizes etc.

Short answer: with a 50 Amp breaker you can pull 40 Amps continously (80%, rule) and the WC needs to be set up so it will report a max current of 40 Amps to a connected car.

Nothing wrong with this setup except you can't charge at 48 Amps. You'd need a 60 Amp breaker and the appropriate wiring for that.
 

STS-134

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If you have a 50 amp breaker installed, your wall connector should be commissioned for a 50 amp breaker and your car should charge at a maximum of 40 amps (80% of 50).

If your car can charge at a full 48 amps on a 50 amp breaker, your setup is misconfigured.
If it cost > $100, I suspect it is a GFCI breaker, and the WC should not be commissioned on it at all. It should be replaced because connecting the WC to a GFCI breaker is specifically against the instructions.
 
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Yep, it is fine to run the wall connector on a 14-50 cord (Tesla even sold a version of it wired up with the cable already for a while). But yes, you only want to draw 80% of the breaker rating continuous. There is a dip switch in the gen 2 to adjust that, and a software config in the gen 3. If you do wire it up that way though, be sure to properly torque all the terminals the wires go into to avoid a high resistance situation (and a fire hazard). And also make sure the 14-50 socket is in good condition and the plug seats in firmly. FYI, my wall connector has been running continuously in my car port for 4 years wired up this way.
 

jjrandorin

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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!


You mixed up a bunch of stuff here in this post.

1. Typical "Dryer plugs" are not 14-50 / 50 amp circuits. They are usually 30 amp circuits
2. Any warnings you may have seen about using existing wiring might be applicable to existing wiring, but not to something you paid an electrician to install
3. Your understanding of the wall connector is mostly correct, however, THE MAX it can pull is 48 amps if it is setup for a 60 amp circuit. If its on a 50 amp circuit, it should be setup that way (and charge at 40amps.

If you are the one who setup the wall connector, then you need to make sure you setup the software for it so that its on a 50 amp circuit and is only pulling 40 amp continuous. If your electrician set it up for you, you can verify it by either looking at the web page for it, or seeing what your car is actually charging at.

Your car should say XX/YY with XX being the amps its charging at, and YY being the max available. if its on a 50 amp circuit, it should say 40/40.

Information is good, but its absolutely possible to "research yourself into a panic", which it sort of sounds like you are doing here.
 
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appleguru

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Mar 15, 2017
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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 wiring is correctly sized; #6 THWN-2 is good up to 75A. It is usually the right size wire for conduit 48A EVSE installs (unless you need to go larger for voltage drop on a long run or to derate for having multiple circuits together in one pipe).

Your dual pole 50A breaker should have been a dual pole 60A breaker per code, since the 48A draw is continuous. With that said, this is *not* a safety issue. Code says breakers should be sized 20% above continuous loads mainly to avoid nuisance trips.

A 50A breaker can and will happily carry 50A 24/7/365 and never trip. And since your 48A load is the only thing on the breaker, you’ll very likely never have an issue.

If you’re worried about it though, or want a technically code compliant install, putting a 60A breaker in is a 10minute job for the electrician since your wire and everything else is already fine. The breaker should be cheap too, since GFCI is not required (nor recommend) for hardwire installs.
 
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Your wiring is correctly sized; #6 THWN-2 is good up to 75A. It is usually the right size wire for conduit 48A EVSE installs (unless you need to go larger for voltage drop on a long run or to derate for having multiple circuits together in one pipe).

Your dual pole 50A breaker should have been a dual pole 60A breaker per code, since the 48A draw is continuous. With that said, this is *not* a safety issue. Code says breakers should be sized 20% above continuous loads mainly to avoid nuisance trips.

A 50A breaker can and will happily carry 50A 24/7/365 and never trip. And since your 48A load is the only thing on the breaker, you’ll very likely never have an issue.

If you’re worried about it though, or want a technically code compliant install, putting a 60A breaker in is a 10minute job for the electrician since your wire and everything else is already fine. The breaker should be cheap too, since GFCI is not required (nor recommend) for hardwire installs.
isn't 60a breaker needs #4 wire, 6/2 or 6/3 for 50a breaker? maybe im wrong.
 
#4 if its romex/NM-B (wire in a sheath), #6 if its individual conductors in conduit(usually THHN or THNN-2 or similar)
This is because of thermal issues, right? And the logic being that if you have individual conductors, there's more space to dissipate the heat? That said, all else being equal, wouldn't #4 be the better choice, due to less voltage drop?
 

Sophias_dad

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This is because of thermal issues, right? And the logic being that if you have individual conductors, there's more space to dissipate the heat? That said, all else being equal, wouldn't #4 be the better choice, due to less voltage drop?
Yes, that's it, and whatever might be combustible will be held further away from the conductors. And yes, #4 would be a generally better choice due to less voltage drop and power waste. But I've never seen 4/2 NMB, and it gets pretty expensive to have three #4 conductors. I assume the NMB also gets REALLY unpleasant to work with at #4 sizes like 4/3.
 

Sophias_dad

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what is nm-b 6/3 wire for 50a or it could also go for 60a?
NM-B is also known by the trade name "Romex", its a cable already made up that contains(usually) 2 or 3 conductors of a given size, plus an uninsulated ground wire of an appropriate size for the conductors that's all wrapped in a single rubbery sheath. The 6/2 or 6/3 refers to the AWG size of the wire, followed by the number of conductors of that size. Side note, I've seen up to 12/4 NMB(usually found in bathrooms or other complex light/fan arrangements)

#6 NM-B wire(6/2 or 6/3) is not allowed to carry 60 amps(or be breakered for 60 amps) because its only rated to 55 amps.
 
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Yes, that's it, and whatever might be combustible will be held further away from the conductors. And yes, #4 would be a generally better choice due to less voltage drop and power waste. But I've never seen 4/2 NMB, and it gets pretty expensive to have three #4 conductors. I assume the NMB also gets REALLY unpleasant to work with at #4 sizes like 4/3.
I have a 4/3 cable run from the panel on one side of the garage to the WC on the other side. Since my garage doesn't have drywall, it was fairly simple to install and doesn't require any sharp bends.
 

Sophias_dad

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I have a 4/3 cable run from the panel on one side of the garage to the WC on the other side. Since my garage doesn't have drywall, it was fairly simple to install and doesn't require any sharp bends.
Not like I'm gonna tell anyone, but I'm pretty sure you aren't allowed to have exposed NM-B in a garage below like 7 feet above the floor. People(including myself, sadly) have a tendency to use the exposed NMB as a convenient way to hold things up in the joist bay. Think driveway reflectors, axes, brooms, whatever will fit behind a chunk of romex that's centered in the bay.
 
Not like I'm gonna tell anyone, but I'm pretty sure you aren't allowed to have exposed NM-B in a garage below like 7 feet above the floor. People(including myself, sadly) have a tendency to use the exposed NMB as a convenient way to hold things up in the joist bay. Think driveway reflectors, axes, brooms, whatever will fit behind a chunk of romex that's centered in the bay.
It runs up the wall (there isn't drywall but there are boards covering the walls) and exits the wall above 7' from the floor, travels across the garage along the beams, then goes down into the other wall which is also covered in boards.
 

SageBrush

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Your wiring is correctly sized; #6 THWN-2 is good up to 75A.
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.
A 50A breaker can and will happily carry 50A 24/7/365 and never trip. And since your 48A load is the only thing on the breaker, you’ll very likely never have an issue.
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.
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I don't remember Sandy's warning but from OP's description it sounds like a reminder to 1, use a dedicated circuit; and 2, to account for continuous usage. The latter means that the wiring is sized for 125% of the maximum amperage draw, and the breaker is sized to protect the wiring.

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. 122F sounds too hot to worry about, unless the conductors are e.g. in a hot attic The safe bet is for OP to set the TWC to a maximum 40 Amp draw. If he wants to swap the breaker to 60 Amps in order to pull 48 Amps he should get his electrician's sign-off to do so. Since this ia a hard-wired circuit for an EVSE, an expensive GFI breaker is not required
 
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mswlogo

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NM-B is also known by the trade name "Romex", its a cable already made up that contains(usually) 2 or 3 conductors of a given size, plus an uninsulated ground wire of an appropriate size for the conductors that's all wrapped in a single rubbery sheath. The 6/2 or 6/3 refers to the AWG size of the wire, followed by the number of conductors of that size. Side note, I've seen up to 12/4 NMB(usually found in bathrooms or other complex light/fan arrangements)

#6 NM-B wire(6/2 or 6/3) is not allowed to carry 60 amps(or be breakered for 60 amps) because its only rated to 55 amps.
Actually since they don’t make 55 amp breakers you are allowed to use a 60 Amp breaker. But you still have to consider it a 55 amp circuit when considering continuous loads. And if you can’t set the load to a 55 A (circuit) you have to round down (e.g. 50 A circuit with a 40 Amp continuous load).
 
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Sophias_dad

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Actually since they don’t make 55 amp breakers you are allowed to use a 60 Amp breaker. But you still have to consider it a 55 amp circuit when considering continuous loads. And if you can’t set the load to a 55 A (circuit) you have to round down (e.g. 50 A circuit with a 40 Amp continuous load).
Yes, I was considering this in the context of an EV charging circuit and didn't want to muddle the waters.
 

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