WC 3rd gen wiring question

[Fat_daddy78]

Just ordered a 3rd gen Wall Connector. Grabbed a 60a breaker but am hearing different opinions on the wire size. I know Tesla said to use 6 gauge at least to get it's full potential. Problem is, I have a pretty long run to my garage from my secondary panel. Will I have to much drop at 60'-70' to achieve 48 amps at the charger using 6/3 Romex? Or would that still provide max power?

 

[UncleCreepy]

With 6 AWG, 70 ft cable length and 48 A you'll get the following results:

Voltage drop: 2.65
Voltage drop percentage: 1.11%
Voltage at the end: 237.35

That's the voltage drop from the cable only. There will be more wiring from the sub panel to the charger and lastly, there is the cable on the charger which gets quite warm at 48 A.
If it's within your budget, I'd run a thicker cable. I use a 1/0 AWG ACWU cable between the main and the sub panel. It's less expensive than a copper cable with similar characteristics.

 

[paulk]

Just ordered a 3rd gen Wall Connector. Grabbed a 60a breaker but am hearing different opinions on the wire size. I know Tesla said to use 6 gauge at least to get it's full potential. Problem is, I have a pretty long run to my garage from my secondary panel. Will I have to much drop at 60'-70' to achieve 48 amps at the charger using 6/3 Romex? Or would that still provide max power?

Romex 6/3 is only rated for 55 amps, individual wires (THWN) in conduit is rated for 65 amps and can get a bit hotter before failure. If it’s a long but simple wire run you should use the biggest wire you can for future expansion and to avoid voltage drop. I had run 2/0 gauge aluminum, which doesn’t even closely fit into the lugs, and had to use a box to change the wire to 3 gauge copper for my gen 2 wall connector. It was a pain to run, but I figured it’s future proof. A year later we got a second Tesla and I was able to share the wire with another gen 2, easy.

If you don’t care about future proofing, you should probably use 4 gauge Romex in a wall space or 6 gauge THWN/THHN in conduit.

Also, you don’t need 3 conductor wire for a wall connector, it only uses two conductors and a ground. That said, I would still run 3 conductors in case a future wall connector uses it.

 

[Rocky_H]

Seconding what @paulk said, 6 gauge Romex is not allowed for a 60A circuit. But beyond just taking people's opinions on the internet, here is a chart of the ampacity ratings for various wire sizes and types:
Ampacity Charts - Cerrowire

That first column is for NM-B, which is Romex, and you can see that the 6 gauge line is only allowed for 55A.

For the next thing, if it were just 5 or 10 feet, sure, whatever, run the fourth unneeded wire--not much cost difference. But for the 70-80 feet you are talking about, that's a noticeable waste of money, and I wouldn't do that if you still have the choice in buying materials at this point.

 

[Fat_daddy78]

With 6 AWG, 70 ft cable length and 48 A you'll get the following results:

Voltage drop: 2.65
Voltage drop percentage: 1.11%
Voltage at the end: 237.35

That's the voltage drop from the cable only. There will be more wiring from the sub panel to the charger and lastly, there is the cable on the charger which gets quite warm at 48 A.
If it's within your budget, I'd run a thicker cable. I use a 1/0 AWG ACWU cable between the main and the sub panel. It's less expensive than a copper cable with similar characteristics.

Doesn't sound like much of a drop in voltage, I wonder how that affects the amperage.

 

[Fat_daddy78]

Romex 6/3 is only rated for 55 amps, individual wires (THWN) in conduit is rated for 65 amps and can get a bit hotter before failure. If it’s a long but simple wire run you should use the biggest wire you can for future expansion and to avoid voltage drop. I had run 2/0 gauge aluminum, which doesn’t even closely fit into the lugs, and had to use a box to change the wire to 3 gauge copper for my gen 2 wall connector. It was a pain to run, but I figured it’s future proof. A year later we got a second Tesla and I was able to share the wire with another gen 2, easy.

If you don’t care about future proofing, you should probably use 4 gauge Romex in a wall space or 6 gauge THWN/THHN in conduit.

Also, you don’t need 3 conductor wire for a wall connector, it only uses two conductors and a ground. That said, I would still run 3 conductors in case a future wall connector uses it.

I can only dream of adding a second Tesla at this point !
But I'd love to "Be Prepared"

 

[Fat_daddy78]

Seconding what @paulk said, 6 gauge Romex is not allowed for a 60A circuit. But beyond just taking people's opinions on the internet, here is a chart of the ampacity ratings for various wire sizes and types:
Ampacity Charts - Cerrowire

That first column is for NM-B, which is Romex, and you can see that the 6 gauge line is only allowed for 55A.

For the next thing, if it were just 5 or 10 feet, sure, whatever, run the fourth unneeded wire--not much cost difference. But for the 70-80 feet you are talking about, that's a noticeable waste of money, and I wouldn't do that if you still have the choice in buying materials at this point.

Appreciate that, I thought the 6g did the job...
Yeah I definitely want to have all the power I can. Unfortunately it is like 35 feet through joists in basement, then through basement concrete wall or band board to attached garage and another 30 feet or so on the basement wall. Not sure if I need conduit there yet. I have gray conduit around my other garage outlets.

 

[Fat_daddy78]

Thanks all!
Guess I better get searching for some heavier wire.
I had the 6/3 to do a 14-50 (much shorter ) for my camper, my original intent was to use that as well.

 

[Sophias_dad]

Doesn't sound like much of a drop in voltage, I wonder how that affects the amperage.

The amperage would still be 48, but the power delivered would be dropped by that same 1.11%... essentially nothing.

And as you have been told, the max you can get out of the 6/3 romex for EV use is 44 amps continuously. Unless you really NEED that extra charging speed, just set the Gen3 to 40amps(or 44 if that's an option)

 

[Rocky_H]

Thanks all!
Guess I better get searching for some heavier wire.
I had the 6/3 to do a 14-50 (much shorter ) for my camper, my original intent was to use that as well.

You always have the choices. You can still use the 6 gauge, but it will just need to be set down to a 50A circuit, not a 60A circuit. That's still 40A continuous supply to the car, and that's still pretty fast charging for at home.

 

[Sophias_dad]

You might find its cheaper to run two 6 gauge conductors and smaller ground in conduit than to get 4/3 or (4/2 if it exists!) romex.

Note that none of these(wires or conduits) need to be run through joists.. they can be face-stapled(assuming other rules about exposed romex are followed). I found 6/2 romex to be fairly easy to work with, being flat.

 

[Sophias_dad]

You might find its cheaper to run two 6 gauge conductors and smaller ground in conduit than to get 4/3 or (4/2 if it exists!) romex.

Note that none of these(wires or conduits) need to be run through joists.. they can be face-stapled(assuming other rules about exposed romex are followed). I found 6/2 romex to be fairly easy to work with, being flat.

Just to clarify my own statement... face stapling is allowed for 8/3 or 6/2 or larger cables... anything less is expected to be drilled through the wood. Obviously if the wire isn't crossing the wood it should be stapled to the side(regardless of size) far enough from the edges that a nail or screw won't be likely to hit it(usually the middle, but if you are dealing with a 2x10, the middle isn't necessary!)

 

[Rocky_H]

Just to clarify my own statement... face stapling is allowed for 8/3 or 6/2 or larger cables... anything less is expected to be drilled through the wood. Obviously if the wire isn't crossing the wood it should be stapled to the side(regardless of size) far enough from the edges that a nail or screw won't be likely to hit it(usually the middle, but if you are dealing with a 2x10, the middle isn't necessary!)

I don't have a citation for this, but I thought Romex was never allowed to be just attached exposed on the surface of a wall. I thought it could be by itself inside a wall, or in a ceiling or crawlspace, but but if you are going to run it along a wall's surface, I thought that needed conduit then.

 

[SilverString]

Doesn't sound like much of a drop in voltage, I wonder how that affects the amperage.

that's not much loss current will likely remain at 48 amps, it surely will not go higher. My 240v often runs at 247v on off peak hours and the car will cut the HPWC down to a 47 amp charge

 

[Sophias_dad]

I don't have a citation for this, but I thought Romex was never allowed to be just attached exposed on the surface of a wall. I thought it could be by itself inside a wall, or in a ceiling or crawlspace, but but if you are going to run it along a wall's surface, I thought that needed conduit then.

Yes, I think its gotta be 7 feet off the floor, and about half of mine is in utility space while the other half is above a drop-ceiling(all above 7 feet)

 

[Fat_daddy78]

Thanks for the added info. I've been looking into 4 awg thhn that's sold by the foot at the big box stores. I think I might grab that today if they have it still.

* On a side note, I haven't got alerts to the newest replies for some reason, I wasn't ignoring them.
Guess I probably need to adjust my notifications somewhere next

 

[Fat_daddy78]

oh, and yes. I want the fastest possible charge. I drive a lot. 100 miles just to/ from work daily, and much more regularly. I hope this car holds up. I already have 2,600 miles on her!

 

[Fat_daddy78]

There's many times I'm only home for a few hours so I need to make the most of it in charging

 

[1100MCM]

I had a short run (4 ft) but I ended up using individual THHN 6 AWG wires rated for 55 A continuous inside 3/4 EMT. I figured 48 A should be no issue for that wire.

 

[gfunkdave]

I had a short run (4 ft) but I ended up using individual THHN 6 AWG wires rated for 55 A continuous inside 3/4 EMT. I figured 48 A should be no issue for that wire. View attachment 550103

It's not about your feelings on the matter. 6 AWG THHN/THWN is good to 65A at the 75C rating, which you probably would use because your circuit breakers are probably rated to 75C.

Furthermore, three 6 AWG wires in a 3/4" conduit is about 28% fill, which is allowed. So regardless of what you figure, it is an OK installation.