Electrician installed wall connector using Romex 8/3 + 60A breaker

[SageBrush]

It's currently in the wall.

That looks OK from the outside. How was it installed behind the drywall ? I ask mostly out of curiosity, and partly because I don't trust your "electrician."

By the way, #6 AWG NM-B is also not rated for 48A continuous use

 

[android04]

I'm not so sure. The conductors are THWN, which would allow corrections and adjustments based on the 75C column of Table 310.16
But UF is in the 60C column

I've had that website that sells the TCERJP cable bookmarked because it is a special cable, it is not UF-B nor NM-B. It's really expensive because it meets or exceeds the requirements of NM-B and UF-B, as well as crush and impact rating of MC cable. You can read more about it here Is TC-ER-JP Cable The Future of Residential Wiring?

 

[SageBrush]

I've had that website that sells the TCERJP cable bookmarked because it is a special cable, it is not UF-B nor NM-B. It's really expensive because it meets or exceeds the requirements of NM-B and UF-B, as well as crush and impact rating of MC cable. You can read more about it here Is TC-ER-JP Cable The Future of Residential Wiring?

Do you have the NEC entry ?

Addendum:

https://www.nema.org/docs/default-source/technical-document-library/tray-cable-for-use-in-residential-applications.pdf?sfvrsn=6a94dacb_2

The last paragraph of page #1 clarifies that the 75C ampacity column is only allowed for generator hookups.

 

[canbonbon]

Tesla Connector Gen 3 Installation Manual on page 6 says this:->

"If installing for maximum power, use minimum 6 AWG, 90° C-rated copper wire for conductors"

 

[240vPlug]

I'm not so sure. The conductors are THWN, which would allow corrections and adjustments based on the 75C column of Table 310.16
But UF is in the 60C column

THHN needs to be in conduit for ampacity rating

 

[240vPlug]

Tesla Connector Gen 3 Installation Manual on page 6 says this:->

"If installing for maximum power, use minimum 6 AWG, 90° C-rated copper wire for conductors"

#6 wire can be used. NM-B Romex is limited to 60C ampacity as someone else pointed out so it's rated ampacity is only 55amp even when rated for 90C.

If your using #6 wire for a TWC at full 48 amps it needs to be in conduit.

Anyone confused yet?

 

[exxxviii]

My one little data point for the NM-B debate... I do not know if this varies by state or common practice. But in my area, all the electricians that my father and I got quotes from were going to use #6 NM-B for a 60A circuit. Some of these were hard core adherents to code, one insisting that a hardwire installation also needed a disconnect switch in sight of the EVSE. Is the above universal?

 

[SageBrush]

Tesla Connector Gen 3 Installation Manual on page 6 says this:->

"If installing for maximum power, use minimum 6 AWG, 90° C-rated copper wire for conductors"

This is correct ... so far as it goes. But adjustments and corrections derate the wire. NM-B sheath is one cause of derating

 

[SageBrush]

I do not know if this varies by state or common practice. But in my area, all the electricians that my father and I got quotes from were going to use #6 NM-B for a 60A circuit.

I don't think this is NEC compliant

 

[AmaziNMoe]

I’m looking to get this done soon as well, would a 6/2 wire like this work or it has to be 6/3? Looking at the installation guide I thought it only needed 3 wires which this one includes the ground, am I mistaken here? 6/2 W/GRND NM-B Romex 600V

 

[SageBrush]

If your using #6 wire for a TWC at full 48 amps it needs to be in conduit.

The #6 AWG wire also has to be copper, and at least 75C rated

NEC says that wires have to be protected, which in residential wiring is going to result in either sheathed in wall, or in conduit not in wall. Confusion reigns because sheathing often derates the wire.

 

[exxxviii]

I don't think this is NEC compliant

Is NEC 334.80 an absolute that must be universally applied to NM-B. Or are there exceptions where an electrician can make adjustments or corrections based on the installation?

 

[howardnj]

I am by no means an electrician but a licensed electrician just installed my Wall Connector using Romex 8/3 and a 60A breaker for a 40ft run. I believe a 60A breaker should use at least Romex 6/3. I realized this after he had left, and just called him back to come rectify. He tried to convince me that because the wall connector draws only 48A, I should be good.

I insisted he come swap it out for a 6 gauge cable, as specified in the Tesla installation guide. Am I wrong?

I hope that you paid by a credit card?
Dispute the charge for poor workmanship and request a charge back. Use a local licensed electrician from the list of recommended electricians on the Tesla web site.

 

[canbonbon]

My one little data point for the NM-B debate... I do not know if this varies by state or common practice. But in my area, all the electricians that my father and I got quotes from were going to use #6 NM-B for a 60A circuit. Some of these were hard core adherents to code, one insisting that a hardwire installation also needed a disconnect switch in sight of the EVSE. Is the above universal?

Same here. I now have 4 quotes and all electricians are saying #6/2 on a 60 Amp circuit. One even said #4/2 does not exist or is rare to find. These folks have installed many Tesla connectors in my town with exact same wire and the town inspection passed. No conduit was required. However, if I insisted on #4 THHN, then they said they would have to use Conduit (as I found out in another thread) and cost of the install went up a lot. I am sticking to #6/2 and lowering the Amps to 40 Amp instead. Planning to get the installation done in next couple of weeks.

So what's confusing me is that how come all electricians in my area (Massachusetts) are wrong and folks on this board are all right? Where did you purchase #4/2 NM-B wire? Even the town inspector seems foolish if he is approving all these #6/2 installs. I now have couple of references in town whom I plan to visit to check out the #6/2 install.

 

[240vPlug]

The #6 AWG wire also has to be copper, and at least 75C rated

NEC says that wires have to be protected, which in residential wiring is going to result in either sheathed in wall, or in conduit not in wall. Confusion reigns because sheathing often derates the wire.

Good points

 

[240vPlug]

I don't agree with #6 NM-B and would never use that. There are many electricians though that will argue till the cows come home it's overkill to use #4 and cite that that can round up.

I always say it's not worth it to try and cut corners or push boundaries when your dealing with an EV charger. #4 NM-B is a lot more expensive and not as available as 6/3 which I believe causes some to try and rationalize using it.

This is why, I believe, the majority of jobs I see are #6 THHN in conduit.

 

[SageBrush]

Is NEC 334.80 an absolute that must be universally applied to NM-B. Or are there exceptions where an electrician can make adjustments or corrections based on the installation?

tl;dr: Sometimes less, not more than the 60C column

Long story:
Adjustments and corrections will not increase the ampacity allowed by the 60C column of Table 310.16. They may result in a lower ampacity. The idea here is that you may apply corrections and adjustments in accordance with the ampacity of the conductor/termination rating, but the final ampacity of NM-B is the LESSER of the 60C column or the adjusted/corrected result using Table 310.16 and the adjustment/correction tables.

 

[SageBrush]

I don't agree with #6 NM-B and would never use that. There are many electricians though that will argue till the cows come home it's overkill to use #4 and cite that that can round up.

Rounding up to the next available breaker size is allowed. No such allowance is allowed for conductors

 

[explosive0]

I think it’s time to fire him and call my county inspector. I hate to because he came recommended from a friend who has a personal relationship with him, and I don’t want to be that guy, but whatever.

I pointed out to him that he either needs to use #4 Romex or #6 MC, and provided him this link as an example - Link

He spewed something about MC being for commercial and not residential. I’ve checked local codes and cannot find anything to support this. At this rate, I’m better off just doing the work myself.

 

[240vPlug]

Rounding up to the next available breaker size is allowed. No such allowance is allowed for conductors

I'm not arguing. It drives me nuts some of the stuff I hear.

The problem with NM-B and EVSE is that the wiring may be in very hot attics, crawl spaces, or exterior walls.