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Plug and 100Amp line sticker shock

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Evan, now that I see the picture of your panel and the NEMA 14-50 directly below it, I think you will be fine with the 8/3 NM-B, being the run is probably less than 5 feet of wire total... The wire he used is rated at 45Amps, the Portable EVSE tops out at 40Amps continuous. Given such a short length of wire, there's nothing to be concerned with. If it really bothers you he could surface mount the 14-50 directly below the panel using a short "nipple", and use individual 6AWG THHN wire, but it's really overkill.

As in these pictures:

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Evan, now that I see the picture of your panel and the NEMA 14-50 directly below it, I think you will be fine with the 8/3 NM-B, being the run is probably less than 5 feet of wire total... The wire he used is rated at 45Amps, the Portable EVSE tops out at 40Amps continuous. Given such a short length of wire, there's nothing to be concerned with. If it really bothers you he could surface mount the 14-50 directly below the panel using a short "nipple", and use individual 6AWG THHN wire, but it's really overkill.

As in these pictures:

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I bet it's no more than 24" of wire, 36" max


Evan, Via Tapatalk
 
I bet it's no more than 24" of wire, 36" max
Even though with the short length it won't present any issues with voltage drop, the reason that the codes exist is to prevent the wire from overheating. The length of the run will not affect the amount the wire heats up under load.

The reason that you have to use 60C ampacities even though the wire itself can withstand 90C is that NM wire is it's typically enclosed in a wall space where heat can easily build up and the wire will be in contact with materials not rated for > 60C exposure. In your install, the wire is in contact with insulation in your wall.

8 AWG wire under 40A of load will be dissipating about 2.4 W/ft. Doesn't seem like a lot, but in an enclosed (and insulated) space under prolonged load, it can be an issue. Going to 6 AWG wire will reduce that to about 1.5 W/ft - close to half. The other alternative would be to run conduit and then individual THHN-2 8 AWG wire. But it's going to be way easier to use 6-3 NM wire than to try to fish conduit through the wall unless he changes the wire to route out the bottom of the panel (in which case you could have surface mounted the outlet as well.
 
Regarding the 50 Amp wire used...
Reply from Tesla:
Hello Evan,

We unfortunately cannot comment on the gauge of wire when installing equipment for charging our vehicles. It is up to your electrician to decide on the gauge given the amperage and voltage that will be flowing through the line. As long as he has selected a gauge thick enough (or more than thick enough) for 50amps @ 220v, than you should be okay.



Also, I was not able to reply all and include your electrician on this email. The way that it was received by our system made me unable to do so. I apologize for the inconvenience.

Kindest regards,

Stephen Smith | Ownership Experience Advocate
3500 Deer Creek Rd. | Palo Alto, Ca 94304
p 1.877.778.3752 | e [email protected]



Reply from my Installer:
Hello Evan,
I have been following this but was waiting till I was able to get back to my office to verify the NEC code for #8 AWG.

The temperature ratings of conductors in article 310.13, at 75 deg. Cel. # 8AWG has a 50 amp rating.

At 90 deg. Cel. #8 AWG has a 55 amp rating.

This is the standard that my inspector would pass my work.


That is why I chose #8 AWG copper wire for this install. You should have more than enough to charge your beautiful car. I am really looking forward to seeing it.

You have asked some great questions and I hope that I have been ale to answer them well for you.

Kind regards,

Nathanael Toms

You've got a friend in the business.

P.S. I like the challenge to go back to my code book, I have never failed an inspection in Springfield yet. I don't want to fail that record.
 
I have been following this but was waiting till I was able to get back to my office to verify the NEC code for #8 AWG.

The temperature ratings of conductors in article 310.13, at 75 deg. Cel. # 8AWG has a 50 amp rating.

At 90 deg. Cel. #8 AWG has a 55 amp rating.
The NEC code doesn't matter if he insists on using the wrong table. He should be using the 60C table for NM wire (Southwire even says this on their website), not the 75-90C table for other grades of wire.
 
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The NEC code doesn't matter if he insists on using the wrong table. He should be using the 60C table for NM wire (Southwire even says this on their website), not the 75-90C table for other grades of wire.

I don't know how to read that table or what the temperature ratings mean. If I'm looking at the table right, however, it seems that my 8ga-3 wire install should be good for 40 amps, right? If it's rated lower, where do you see that/how do I read the table. I forwarded your message to my installer (who's probably well and sick of me and thinking he should have charged a LOT more!).
 
I don't know how to read that table or what the temperature ratings mean. If I'm looking at the table right, however, it seems that my 8ga-3 wire install should be good for 40 amps, right? If it's rated lower, where do you see that/how do I read the table. I forwarded your message to my installer (who's probably well and sick of me and thinking he should have charged a LOT more!).

Evan, It looks like you have a dispute. Take the table, your photo of the wire, and go to the county inspectors office. Offer for your electrician to attend with you. I believe your problem will end quickly.

Your instllation requires 50 amps. 40 amps for continuous draw. He only supplied wire for 40 amps and 32 continuous. He needs to re-do his work IMO.
 
Evan, It looks like you have a dispute. Take the table, your photo of the wire, and go to the county inspectors office. Offer for your electrician to attend with you. I believe your problem will end quickly.
I don't get the impression the installer has pushed back yet. I'd give him/her a chance to respond responsibly before heading to the inspector.
 
Evan, It looks like you have a dispute. Take the table, your photo of the wire, and go to the county inspectors office. Offer for your electrician to attend with you. I believe your problem will end quickly.

Your instllation requires 50 amps. 40 amps for continuous draw. He only supplied wire for 40 amps and 32 continuous. He needs to re-do his work IMO.

Ok, sent an email politely asking that he change out the wiring. Didn't bring up the threat of an inspection at this point. Hoping he'll just come over and change out the $10 worth of wire to be rid of me!


Evan, Via Tapatalk
 
For such a short run of wire, the cost is negligible. Even if it did barely meet code(it doesnt as stated by others), why risk it? Its definately not worth possibly burning the house down. Your electrician should have known better, but by the looks of your install, it's a half assed job. Any reputable installer would have mounted the panel flush. It only takes a bit more time, but looks much more professional.
 
Wow, big project! Hope it goes well.

It did. The old cable was used to pull new "compact conductors" (trapezoid-shaped instead of round) through the existing flex conduit and with enough "rope soap" the cables slid easily through; the old conductors were 00-ga. and the new can handle 350A. The co-op supervisor was very surprised that I was able to run as much as I did through 00-ga. conductors off a transformer rated at only 15 Kva without causing light dimming (and their computer system said that at times I was drawing 195% of rated capacity). All the other assorted goodies (including the meter) were replaced, the transfer switch was added, and we exchanged 11 circuits between panels with little trouble.

There is some work left to do, yet - Monday or Tuesday they will be back to install the 100A sub-panel in the garage. I elected not to put any 240V receptacles onto the standby power sources, figuring that if we have enough of an issue to create a multi-day outage, that 120V will be just fine for charging the Model S. :)

I elected to do a 100A run to a sub-panel in the garage, and from that sub-panel I will connect both the HPWC and an additional 14-50 outlet. Most times I will charge at 40A but I need the 80A capability for those handful of times throughout the year that I need to come back from a business trip and charge up very quickly, then get on the road.

Work's being done by my brother-in-law's father, so I didn't bother to get a quote at all... The sticker shock comes later. :)
 
Got the following email today from Nathanael:

Good morning Evan,
I am hearing you and your concerns. I will fully replace that #8/3 wire to #6/3 w/ ground on my cost, and will bring that receptacle cover when I do this replacement. When would your schedule work for me to arrive and do this work, I am out about 2 weeks?
I apologize for the stress this has caused you. I am proud of you for your research in this.

Kind regards,
Nathanael Toms


Evan, Via Tapatalk
 
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NEMA 14-50 wiring upgrade to 6 gauge

Hey folks,
My electrician came back out today and, free of charge and, honestly, free of hassle, upgraded the wiring to 6 gauge ROMEX for the NEMA 14-50 outlet. I feel much better knowing that it should be a bit safer and that there's that extra margin of safety...don't need to be the next "EV burns down house" story!

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2012-10-01 12.29.33 by efusco, on Flickr

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2012-10-01 12.31.00 by efusco, on Flickr

I'm all set to get the HPWC installed as well as soon as Tesla gets UL certification and ships it out.

- - - Updated - - -

(off-topic)
@efusco with that lawn you may want to make sure your are going electric on your mower too..

A buddy of mine got one of these and they work like a charm - like a Roomba for your lawn! (that can cut in straight lines and is quieter than ICE mowers)
RL2000 Lawn Mower - Robotic Lawn Mowers and Mulch Mowers | Robomow
It's an interesting idea, and considering what we pay for lawn mowing could, potentially, be economical for us. That said, we live on 5.5 acres of some pretty variable terrain that I think would require a team of electric mower bots to cover!