Heat issue on the new Tesla Ver 3 wall connecter

[Nakk]

Yeah, lowest common denominator for sure.



I think you are referencing the “next size up” breaker rule.

While it sounds useful for wall connectors it never is. The reason is that the wall connector is only settable to limited steps that correspond with breaker sizes. So you set it to 48 amps on a 60a capable wire and breaker. On a 55a capable wire (like 6 gauge romex you have to set it to 40 amps since 48amps would be too high for the wire). At that point you may as well use a 50a breaker. (But legally I think you could use a 60a breaker the way the rule reads, but there would be no point and it would just reduce safety slightly).

This *would* be useful if they let you set the wall connector to 44 amps. Then you could use a 60a breaker on 6 gauge romex and get every last bit of legal capacity out (assuming no other deration needed). I suspect the v3 wall connector could do this in software (does it?).

But I am guessing Tesla has no desire to run that close to the margins. Less house fires due to EV charging is good for business.

I think this quote from the installation manual is key:

"Note: Refer to the circuit breaker current
ratings specified on IEC 60898 when installing
the Wall Connector. If in doubt, check with
your local building electrical inspector."

The way I read the rule is that you can use the next size up breaker. 60a. The continuous load can not exceed the ampacity capability of the wire, in this case the capacity is 55 amps and the max continuous load is regulated to 48 amps. (This assumes you have not branched the circuit to include an outlet or another load other than a networked wall charger.) You set the wall charger to 48 amps based on the circuit breaker size of 60 amps. From page 21 of the Version 2 charger:

"3. Set the rotary switch for the appropriate
current setting supported by your circuit
breaker. Typical circuit breaker ratings are:
15A, 20A, 25A, 30A, 35A, 40A, 45A, 50A,
60A, 70A, 80A, 90A, and 100A"

Since 48 is under the capacity of 55 amps, I believe this is a legal installation. That said, I would absolutely draw a permit and check with the inspector first. If the installation is OK with the inspector I'd feel good about it. If not, I'd change the installation.

The best advice I can give anyone is ALWAYS get a permit. The inspector will make sure code is followed which means you will have a good installation. In my experience, 99% of the time a contractor is willing to work without a permit it means he wants to be able to cut corners without an inspector making sure he does his job correctly. I'm sure not all contractors are like that, but every one I've dealt with that suggested a permit was a waste of time and money tried to cut corners. I learned, ALWAYS pull a permit.

 

[eprosenx]

I think this quote from the installation manual is key:

"Note: Refer to the circuit breaker current
ratings specified on IEC 60898 when installing
the Wall Connector. If in doubt, check with
your local building electrical inspector."

The way I read the rule is that you can use the next size up breaker. 60a. The continuous load can not exceed the ampacity capability of the wire, in this case the capacity is 55 amps and the max continuous load is regulated to 48 amps. (This assumes you have not branched the circuit to include an outlet or another load other than a networked wall charger.) You set the wall charger to 48 amps based on the circuit breaker size of 60 amps. From page 21 of the Version 2 charger:

"3. Set the rotary switch for the appropriate
current setting supported by your circuit
breaker. Typical circuit breaker ratings are:
15A, 20A, 25A, 30A, 35A, 40A, 45A, 50A,
60A, 70A, 80A, 90A, and 100A"

Since 48 is under the capacity of 55 amps, I believe this is a legal installation. That said, I would absolutely draw a permit and check with the inspector first. If the installation is OK with the inspector I'd feel good about it. If not, I'd change the installation.

The best advice I can give anyone is ALWAYS get a permit. The inspector will make sure code is followed which means you will have a good installation. In my experience, 99% of the time a contractor is willing to work without a permit it means he wants to be able to cut corners without an inspector making sure he does his job correctly. I'm sure not all contractors are like that, but every one I've dealt with that suggested a permit was a waste of time and money tried to cut corners. I learned, ALWAYS pull a permit.

My apologies for being blunt, but NO this is absolutely wrong (and the record needs to be corrected here so that others don’t try it).

The issue is that EV charging is explicitly called out in the NEC as “a continuous load”. Continuous loads must have wire and breaker ampacity that is 125% of the load. So at 48 amps of continuous load you must have wire and breaker ampacity of at least 60 amps.

I should also call out that you are not allowed to put a receptacle and a wall connector on the same circuit.

As a side note, I will always recommend a permit, but I will also call out that most inspectors really don’t know everything. I have seen lots of shady stuff “passed” that never should have been.

Getting stuff inspected is good, but don’t assume it will 100% protect you.

 

[Gadget-X]

Just for completeness. The local code required an in garage cutoff switch. The installation notes says not to install any cutoff switch between Breaker and Wall Connector. The breaker is a 60amp and all wire id 6 ga copper stranded. The breaker has cooled down almost 12 deg f since he removed the cutoff switch. Inspected and done with this now. Breaker is running 103 Deg F for 48AMP during a 2 1/2 hour charge. Thank you everyone who took the time to reply.

M

 

[Nakk]

My apologies for being blunt, but NO this is absolutely wrong (and the record needs to be corrected here so that others don’t try it).

The issue is that EV charging is explicitly called out in the NEC as “a continuous load”. Continuous loads must have wire and breaker ampacity that is 125% of the load. So at 48 amps of continuous load you must have wire and breaker ampacity of at least 60 amps.

I should also call out that you are not allowed to put a receptacle and a wall connector on the same circuit.

As a side note, I will always recommend a permit, but I will also call out that most inspectors really don’t know everything. I have seen lots of shady stuff “passed” that never should have been.

Getting stuff inspected is good, but don’t assume it will 100% protect you.

Please don't apologize! Be blunt. I prefer learning the truth to someone trying to coddle my feelings, LOL. What I missed is wire AND breaker requirement to be 125% of a continuous load. What I could find listed the requirement for the breaker but not the wire. The way I read it was that the wire size had to support the breaker, and that you could step up the breaker to the nearest size as long as regulated current was under the ampacity of the wire. Could you please reference where I can find the dual requirement for the 125% on wire and breaker? I am not saying you are wrong, my guess is you are right. But I can't find the requirement and I'd like to be able to reference the code. Thanks!!

 

[Gadget-X]

This is what the Florida Residential code says for breakers...

M

 

[Nakk]

This is what the Florida Residential code says for breakers...

Right. That's where it requires that the breaker be 125% of the load. I'm still looking for where the ampacity of the wire is required to be 125% of load. I found a section that requires the regulated load to be under the ampacity of the wire, but I can't find the 125% requirement for the amapacity of the wire.

 

[Gadget-X]

This is all I found for branch circuits ...

M

 

[SilverString]

I think this quote from the installation manual is key:

"Note: Refer to the circuit breaker current
ratings specified on IEC 60898 when installing
the Wall Connector. If in doubt, check with
your local building electrical inspector."

The way I read the rule is that you can use the next size up breaker. 60a. The continuous load can not exceed the ampacity capability of the wire, in this case the capacity is 55 amps and the max continuous load is regulated to 48 amps. (This assumes you have not branched the circuit to include an outlet or another load other than a networked wall charger.) You set the wall charger to 48 amps based on the circuit breaker size of 60 amps. From page 21 of the Version 2 charger:

"3. Set the rotary switch for the appropriate
current setting supported by your circuit
breaker. Typical circuit breaker ratings are:
15A, 20A, 25A, 30A, 35A, 40A, 45A, 50A,
60A, 70A, 80A, 90A, and 100A"

Since 48 is under the capacity of 55 amps, I believe this is a legal installation. That said, I would absolutely draw a permit and check with the inspector first. If the installation is OK with the inspector I'd feel good about it. If not, I'd change the installation.

The best advice I can give anyone is ALWAYS get a permit. The inspector will make sure code is followed which means you will have a good installation. In my experience, 99% of the time a contractor is willing to work without a permit it means he wants to be able to cut corners without an inspector making sure he does his job correctly. I'm sure not all contractors are like that, but every one I've dealt with that suggested a permit was a waste of time and money tried to cut corners. I learned, ALWAYS pull a permit.

Wow. I am glad I live in Texas where I just pulled #6 through the wall to my Cool As A Cucumber hard wired HPWC and 60 amp breaker. Austin Energy has zero regulatory past the meter outside the city limits and we like it that way!

 

[Nakk]

Wow. I am glad I live in Texas where I just pulled #6 through the wall to my Cool As A Cucumber hard wired HPWC and 60 amp breaker. Austin Energy has zero regulatory past the meter outside the city limits and we like it that way!

It's not Austin energy, it's your city, county or state. And it does apply to you. If you have a fire and your wiring is determined to be overloaded and not up to code, insurance will not cover your loss. The vast majority of code is there for your benefit; it is there to protect you. Any time you don't follow code, you are risking burning down your home, and possibly killing all or some of your loved ones. Seriously. This is exactly why it's important that we get a definitive answer to the wire ampicity overload requirement. Until we have a code reference, you really should change your HPWC current limit to 40 amps to be safe.

 

[Gadget-X]

Nakk, Somewhat confused here. Why should he lower his HPWC to 40 Amps? 6 gauge twisted copper is code and called for in installation of the Tesla Gen 3 Wall Connector. Are you saying he should have 4 gauge twisted copper wire? Why would the installation manual call for 6 Gauge? Is it wrong?

Thank You

M

 

[Nakk]

The issue is that EV charging is explicitly called out in the NEC as “a continuous load”. Continuous loads must have wire and breaker ampacity that is 125% of the load. So at 48 amps of continuous load you must have wire and breaker ampacity of at least 60 amps.

Found it. And as I guessed eprosenx is correct. Thanks for being blunt!!!

2014 Code Language:

210.19(A)(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of 210.19(A)(1)(a) or (b).

(a) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.

(b) The minimum branch-circuit conductor size shall have an allowable ampacity not less than the maximum load to be served after the application of any adjustment or correction factors.

If you have #6 romex feeding your HPWC, IMMEDIATELY reduce max current to 40 amps. If it's all #6 THHN, you are good for 48 amps. Does that sound good to you eprosenx?

 

[SilverString]

Found it. And as I guessed eprosenx is correct. Thanks for being blunt!!!



If you have #6 romex feeding your HPWC, IMMEDIATELY reduce max current to 40 amps. If it's all #6 THHN, you are good for 48 amps. Does that sound good to you eprosenx?

I should have been more clear here - I call everything Romex because I am old, I believe I did use THHN but I am not sure and not concerned because my "run" is only 15 inches from the breaker box. So in my individual case if you apply the NEC ampacity ratings which are for a 100ft run and adjust them to 15 inches, or even 15 feet I am well within a safe tolerance with standard romex no matter what anybody's code states. This is simple Ohms law based off the resistance of the wire itself, and in my case there is so little that the run never changes ambient temp at any point during a full 10% to 90% 48 amp charge.

I am not suggesting that anyone ignore code, or be unsafe, but saying I should replace my breaker and step down the amps is simply nonsense. My HPWC, with it's built-in overload, GFI, and other safety features is is far less likely to be the cause of a fire than operating my, electric dryer, or my electric oven.

 

[Gadget-X]

I should have been more clear here - I call everything Romex because I am old

Hey wait a minute I represent that old fart bit.....

M

 

[Nakk]

I call everything Romex because I am old, I believe I did use THHN but I am not sure.

Romex these days is a generic term for sheathed cable. So you have two or three conductors and a ground all wrapped up in a plastic sheath so it's one cable. It's not all "romex", but is commonly called romex just like all cola drinks are called "coke." THHN and THWN are an individual insulated wire run through raceways or conduit. #6 THHN and THWN wires have an ampacity of 65 to 75 amps, so both would be good for 48 amps with a 125% correction. Most of the romex actually has THHN wire inside, but is ampacity limited because of the sheath. I used to think you could just strip the sheath off and have THHN wires, but they aren't labeled individually and so don't pass inspection.

 

[Nakk]

Nakk, Somewhat confused here. Why should he lower his HPWC to 40 Amps? 6 gauge twisted copper is code and called for in installation of the Tesla Gen 3 Wall Connector. Are you saying he should have 4 gauge twisted copper wire? Why would the installation manual call for 6 Gauge? Is it wrong?

Sorry, I just saw this. If you look in my post above I think it explains this. Individual 6 gauge THHN and THWN wires have an ampacity of 65 to 75 amps, so good to go. Once those wires are wrapped in a sheath to become romex cable, the ampacity drops to 55 amps because of the heat. So 44 amps is the max continuous load. Unfortunately, the HPWC doesn't have a setting for 44 amps. It's 40 or 48. 48 is too high so we are left with 40 amps if there is any 6 gauge romex cable in the installation. If it's all 6 gauge THHN or THWN, 48 amps is good.

 

[Gadget-X]

Thanks the electrician just texted me to let me know he used all #6 THHN individual wires... Total run was 18ft.

M