Wiring for Wall Connector

[Cosmacelf]

So that's interesting. My NM-B run is 27', through an insulated utility closet. Wall Connector is inside an enclosed garage that's adjacent to the utility room. If the conductors are the same, and it's the vinyl jacket temp rating which is the cause for the 55A rating - then I should be good to go @ 60A considering my installation conditions?

By code no, in practice, well, there’s a reason why electricians continue to make this mistake…

If it were me, I’d let it slide and use it at 48A.

 

[Chewy13]

You cannot use #6 NM-B in a 60A circuit, please read post #3. You must set your wall connector as being on a 50A circuit and you should use a 50A breaker.

So reading the cutsheet on the wire used (CERROMAX-A Slipwire SLP NM-B 6-2) https://www.cerrowire.com/wp-content/uploads/2023/04/Cerrowire-CerroMax-NMB_sheet_230427.pdf

It's rated 90C insulation. Looking at NFPA NEC 310.16 - https://www.nfpa.org/~/media/Files/Code or topic fact sheets/NECAmpacityWorkflow.pdf
It shows #6 is good for up to 75A. Am I misreading/interpreting it?

Edit: Found this graphic on THD from Cerrowire. Like past posts in this thread, NM-B 6/2 is 55A. https://images.thdstatic.com/catalog/pdfImages/b8/b8700922-de06-47dc-b10f-06cb5bab9500.pdf
I'll leave the Wall Connector set up for 50A, better safe than sorry - and meeting code.

 

[Cosmacelf]

So reading the cutsheet on the wire used (CERROMAX-A Slipwire SLP NM-B 6-2) https://www.cerrowire.com/wp-content/uploads/2023/04/Cerrowire-CerroMax-NMB_sheet_230427.pdf

It's rated 90C insulation. Looking at NFPA NEC 310.16 - https://www.nfpa.org/~/media/Files/Code or topic fact sheets/NECAmpacityWorkflow.pdf
It shows #6 is good for up to 75A. Am I misreading/interpreting it?

I don't think that means anything. Southwire also advertises their insulation as being capable of being used in 90 degree C environments (https://assets.southwire.com/ImConvServlet/imconv/cc9ee246a3e9a87c880b862c8b599829546d060e/origin?hybrisId=otmmHybrisPRD&assetDescr=Romex Brand SIMpull Indoor Wire Copper NM-B Cable) but they are honest enough to say ampacity is limited to 60 degree conductors, ie 55 A.

And I apologize, they are PVC jacketed, not just “vinyl”, but the restriction is the same.

As to why this is the case … well I did some more research right now, and the NEC code warriors on the Internet appear stumped. So my statement that this has to do with the insulation melting might not be true. So I have no idea why. But I do know the NEC says 55A max.

But here, use Cerrowire’s own ampacity calculator: Ampacity Calculator

You’ll Find that 6 gauge NM-B has a maximum ampacity of 55A.

 

[sleepydoc]

And I apologize, they are PVC jacketed, not just “vinyl”, but the restriction is the same.

You do know that the ‘V’ in PVC stands for vinyl, right?

As to why this is the case … well I did some more research right now, and the NEC code warriors on the Internet appear stumped. So my statement that this has to do with the insulation melting might not be true. So I have no idea why. But it do know the NEC says 55A max.

The thing all of us need to keep in mind is that the NEC has many people with far more experience and knowledge than any of us. They have nothing to gain by making the code more conservative than it needs to be. Thinking ‘they must have missed something’ is essentially arrogance saying that you think you know more than they do.

 

[Cosmacelf]

You do know that the ‘V’ in PVC stands for vinyl, right?

Yeah I did actually know that, just trying to be 100% accurate here since we are talking about picky points and I wanted to pre-emptively stop someone from saying something.

The thing all of us need to keep in mind is that the NEC has many people with far more experience and knowledge than any of us. They have nothing to gain by making the code more conservative than it needs to be. Thinking ‘they must have missed something’ is essentially arrogance saying that you think you know more than they do.

True. I asked Chat GPT 4 about this, and, well, I remain confused: ChatGPT

 

[fholbert]

My head hurts.

Is all the confusion caused by using Romax? I simply pulled 6 AWG copper wire 45’ though 1” PCV conduit. It’s visible in the garage and I didn’t like the look of exposed Romax or flex.

 

[sleepydoc]

My head hurts.

Is all the confusion caused by using Romax? I simply pulled 6 AWG copper wire 45’ though 1” PCV conduit. It’s visible in the garage and I didn’t like the look of exposed Romax or flex.

Perfect! How many amps is your circuit? That should be good for 50 amps and if you want to upgrade you can pull thicker wire.

The other warning I have is to make sure your connections are all torqued properly - a bad connection can negate properly sized wire and be a fire risk.

All of this is a good illustration of what you pay an electrician for. It’s big just the materials and labor but the knowledge of how to do the job properly.

 

[fholbert]

Perfect! How many amps is your circuit? That should be good for 50 amps and if you want to upgrade you can pull thicker wire.

The other warning I have is to make sure your connections are all torqued properly - a bad connection can negate properly sized wire and be a fire risk.

All of this is a good illustration of what you pay an electrician for. It’s big just the materials and labor but the knowledge of how to do the job properly.

There was a retired 50amp in the box, so I went with that.

Had I realized how much material cost, I may have hired an electrician.

 

[sleepydoc]

There was a retired 50amp in the box, so I went with that.

Had I realized how much material cost, I may have hired an electrician.

Yeah, but the materials wouldn’t have been any cheaper and labor costs aren’t cheap, either!

I have the exact same setup - you should be good. Now just enjoy your car!

 

[Chewy13]

So reading the cutsheet on the wire used (CERROMAX-A Slipwire SLP NM-B 6-2) https://www.cerrowire.com/wp-content/uploads/2023/04/Cerrowire-CerroMax-NMB_sheet_230427.pdf

It's rated 90C insulation. Looking at NFPA NEC 310.16 - https://www.nfpa.org/~/media/Files/Code or topic fact sheets/NECAmpacityWorkflow.pdf
It shows #6 is good for up to 75A. Am I misreading/interpreting it?

Edit: Found this graphic on THD from Cerrowire. Like past posts in this thread, NM-B 6/2 is 55A. https://images.thdstatic.com/catalog/pdfImages/b8/b8700922-de06-47dc-b10f-06cb5bab9500.pdf
I'll leave the Wall Connector set up for 50A, better safe than sorry - and meeting code.

Figured I'd close the loop on this one.. swapped out to a 50A two pole breaker today. (Already set the Wall Connector to 40A output yesterday.)

 

[kpanda17]

I have 2x gen 3s running on dedicated 60 amp breakers and I did 4 gauge for each to be covered. For 48 amps, go with 4 gauge. For 40 amps, 6 gauge works.

 

[sleepydoc]

I have 2x gen 3s running on dedicated 60 amp breakers and I did 4 gauge for each to be covered. For 48 amps, go with 4 gauge. For 40 amps, 6 gauge works.

Just to clarify, I think you meant for 48A charging on a 60A circuit go with 4 gauge and for 40A charging on a 50A circuit 6 gauge works.


One other point to make is that EV charging circuits are ‘continuous duty’ since they may be used for hours at a time. This leads to more heat build up than with intermittent use. Just another reason not to push the limits on the wire size.

 

[fholbert]

I think one, maybe two of you guys may be licensed electricians, but others appear to be “internet experts” who I wouldn’t use to change a light bulb. The conflicting information found in the threads regarding setting up a home charging system is over the top. Without pointing fingers, some people posts are disagreeing with themself in the same thread.

I‘m not an electrician, but have been a project superintendent for the general contractor on a couple of high rise buildings In Los Angeles and Orange County where building codes are pretty strict.

 

[kpanda17]

Just to clarify, I think you meant for 48A charging on a 60A circuit go with 4 gauge and for 40A charging on a 50A circuit 6 gauge works.


One other point to make is that EV charging circuits are ‘continuous duty’ since they may be used for hours at a time. This leads to more heat build up than with intermittent use. Just another reason not to push the limits on the wire size.

Yes
48 amp charging use 4+60
40 amp charging use 6+50

 

[h2ofun]

Wow, glad I decided to check this thread. Had a licensed electrician do my install, and had him pull a permit for my Wall connector.
Used the Romex 6-2 and wired it to a 60A breaker. Only reason I knew that was because I checked the jacket he threw in the trash to see what he used. Damn.
I just jumped into the web interface of the charger and changed it to 50A service…

That is NOT to code. You say you had a permit? If so, did the inspector approve?

I have this happen to me on my solar inverter. I had to talk to the inspector and say it was wrong. He called me back
and said yep, I was right. He called the installers to get them to replace with 4/2 which meets code

 

[Chewy13]

That is NOT to code. You say you had a permit? If so, did the inspector approve?

I have this happen to me on my solar inverter. I had to talk to the inspector and say it was wrong. He called me back
and said yep, I was right. He called the installers to get them to replace with 4/2 which meets code

Yeah, I paid extra for the electrician to pull a permit. Honestly I was going to do the work myself until I realized National Grid would give me $700 back on installation costs. (Work was $960, $700 rebate would make my out of pocket $260 for installing my Wall Connector; $75 was for pulling the permit, the town charges $25 for the permit.)
I double checked with the town, and it shows a permit was pulled, coincidentally the electrician emailed me a copy of the permit today.
Never saw a town inspector come and look at the work, though I noticed the electrician was taking pictures and texting someone - so I wonder if it was inspection via text message...
I'm 50/50 on reaching out to the electrical inspector - work's really busy right now, I've already swapped to a 50A breaker, and while I might miss out on that extra 8A - especially since I'm trying to max SOC at 50%, and charge only when I hit 20-25%, and in the off chance I'm going out and want some extra range before heading out; I probably won't miss the extra capacity, since I target 9 PM charging for off-peak rates and I'll be topped off by the morning.
idk. I'm torn. There's the principle of it, and there's the inconvenience of trying to fight/fix it..

 

[Jerryr]

Interesting

I am getting my Wall Connector installed Tuesday of next week. My electrician stated for a 60 amp service he could not legally use Romex (NM-B) He is going to use 6 AWG “Copper Service Entrance” cable for the run from the breaker panel, though the attic. Then conduit down the garage wall and transition to flex to the Tesla Wall Connector. He said that Service Entrance cable was rated for I believe 65 amps where Romex was only rated for 55 amps.

He charges actual material cost and bills his labor rate for the actual number of hours it takes. He said he estimated it at 3 hours and that would be $800 total. If would likely only take 2 hours and if so the charge would be less. It’s 50 feet of Service entrance cable, conduit where it comes down the garage wall from the attic and any other parts needed.

I’ll post update after it’s installed.

 

[h2ofun]

Interesting

I am getting my Wall Connector installed Tuesday of next week. My electrician stated for a 60 amp service he could not legally use Romex (NM-B) He is going to use 6 AWG “Copper Service Entrance” cable for the run from the breaker panel, though the attic. Then conduit down the garage wall and transition to flex to the Tesla Wall Connector. He said that Service Entrance cable was rated for I believe 65 amps where Romex was only rated for 55 amps.

He charges actual material cost and bills his labor rate for the actual number of hours it takes. He said he estimated it at 3 hours and that would be $800 total. If would likely only take 2 hours and if so the charge would be less. It’s 50 feet of Service entrance cable, conduit where it comes down the garage wall from the attic and any other parts needed.

I’ll post update after it’s installed.

Yep, an electrician who knows code!!!!

 

[h2ofun]

Yeah, I paid extra for the electrician to pull a permit. Honestly I was going to do the work myself until I realized National Grid would give me $700 back on installation costs. (Work was $960, $700 rebate would make my out of pocket $260 for installing my Wall Connector; $75 was for pulling the permit, the town charges $25 for the permit.)
I double checked with the town, and it shows a permit was pulled, coincidentally the electrician emailed me a copy of the permit today.
Never saw a town inspector come and look at the work, though I noticed the electrician was taking pictures and texting someone - so I wonder if it was inspection via text message...
I'm 50/50 on reaching out to the electrical inspector - work's really busy right now, I've already swapped to a 50A breaker, and while I might miss out on that extra 8A - especially since I'm trying to max SOC at 50%, and charge only when I hit 20-25%, and in the off chance I'm going out and want some extra range before heading out; I probably won't miss the extra capacity, since I target 9 PM charging for off-peak rates and I'll be topped off by the morning.
idk. I'm torn. There's the principle of it, and there's the inconvenience of trying to fight/fix it..

What did you pay for?

 

[Chewy13]

What did you pay for?

Copy paste from the paid invoice:

Installed a 240 volt 60 amp circuit