FAQ: Home Tesla charging infrastructure Q&A

[tga]

@DanInSunnyFL could run 6/3 romex through the block wall instead of conduit. I don't know if inside the block of an exterior wall is considered a wet location, which would require UF cable (more expensive).

For a longer run I'd install a 6-50 (not a 14-50), use 6/2, and spend $35 on a 6-50 adapter. Neither the HPWC nor the UMC use the neutral. Once you get over 25 ft of wire, the cost savings for 6/2 pays for the 6-50 UMC adapter. The 14-50 is kind of dumb; it's a hold-over from the pre-supercharger days when people on road trips charged at campgrounds. Now we're stuck with it.

Although it may be hard to find an outdoor, weatherproof 6-50. Outdoor 14-50's are sold for RV use, etc. So you may need to go with 6/3 anyway...

 

[FlatSix911]

I'd like to do something similar to TampaRich at our new house. I am very familiar with the labor side of running electric lines but I'm not intelligent about requirements so I'll ask here.

FlasherZ, I would like similar setup to Rich, but my HPWC will be located outside. I will probably feed the 50A breaker from the main panel (also outside). It has a run through conduit into the attic and then it's exposed. The HPWC & NEMA plug (possibly) will be outside, on a concrete block wall.

Questions:
1. THWN #6 because it's outdoors and 50A? 30' run.
2. With a rear feed the HPWC and the NEMA box do I need to run conduit? I plan on feeding down through the concrete block wall.
Thanks,
Dan

Dan, I have a similar installation with THWN #6... just be sure to place a warning label to not use both plugs at the same time

 

[PV-EV]

If you are concerned about meeting NEC code, 625.40 says each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.

 

[miimura]

The proper way to put two devices like a Wall Connector and a 14-50 outlet on the same circuit is to use a double throw switch like this one.

That ensures that only one load is powered at a time.

 

[israndy]

If you are concerned about meeting NEC code, 625.40 says each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.

Wow! Then what is the point of Tesla's Wall Charger being able to load share with others? Wouldn't that be so you can have a 100+ amp circuit feeding where the chargers sit? One car takes 80 amps, two cars can take 48 amps each, three cars can take 32 amps each? That seems to be how the destination chargers at the M8trix Casino San Jose are wired.

Or are we talking the difference between hardwired and outlets?

-Randy

 

[robby]

Wow! Then what is the point of Tesla's Wall Charger being able to load share with others? Wouldn't that be so you can have a 100+ amp circuit feeding where the chargers sit? One car takes 80 amps, two cars can take 48 amps each, three cars can take 32 amps each? That seems to be how the destination chargers at the M8trix Casino San Jose are wired.

Or are we talking the difference between hardwired and outlets?

-Randy

Correct, outlets are treated differently than hardwired fixtures. 625.40 would not apply to the HPWC (so long as you hardwire it, as instructed).

 

[gilscales]

I don't know if inside the block of an exterior wall is considered a wet location

It would.

 

[tga]

Wow! Then what is the point of Tesla's Wall Charger being able to load share with others? Wouldn't that be so you can have a 100+ amp circuit feeding where the chargers sit? One car takes 80 amps, two cars can take 48 amps each, three cars can take 32 amps each? That seems to be how the destination chargers at the M8trix Casino San Jose are wired.

Or are we talking the difference between hardwired and outlets?

-Randy

What you are considering an "outlet" is called a "receptacle" in the NEC. In NEC terms, an "outlet" is just a connection point. It is not limited to a plug-and-receptacle connection, as you might think. From the 2011 NEC (2017 similar):

Outlet. A point on the wiring system at which current is taken to supply utilization equipment.
Receptacle. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke.
Receptacle Outlet. An outlet where one or more receptacles are installed.

I think 625.40, as discussed by @PV-EV above, is new to 2017. There is no 625.40 in 2011, and 625.40 in 2014 is completely different (circuit needs to be sized for continuous load). At quick glance, I don't see anything like this in NEC 2011 or 2014. So unless your community has adopted 2017, it's probably a non-issue. If you are on 2017, a subpanel with a dedicated breaker for each Wall Connector solves the problem.

Correct, outlets are treated differently than hardwired fixtures. 625.40 would not apply to the HPWC (so long as you hardwire it, as instructed).

2017 NEC 625.40 talks about outlets, not receptacles (see above), so it would apply to either a 14-50 or hardwired Wall Connector.

 

[tga]

It would.

It definitely is when below grade/in contact with soil (ie, a basement wall), but I couldn't find anything definitive for a block wall above grade. I'd probably use UF anyway to be safe.

 

[gilscales]

It definitely is when below grade/in contact with soil (ie, a basement wall), but I couldn't find anything definitive for a block wall above grade. I'd probably use UF anyway to be safe.

Block walls being porous would make them the same as an outdoor location.

Under 334.12 any inspector would site that a block wall would fall under the embedded in concrete restriction.

334.12

Uses Not Permitted

Type NM, NMC, and NMS cannot be used in any dwelling not permitted in 334.10(1), (2), and (3); as service entrance cable; exposed in suspended or dropped ceilings in other than one family, two family, and multifamily dwellings; in commercial garages; in motion picture studios; in theatres and the like unless otherwise provided in the NEC®; in hoistways or on elevators or escalators; in storage battery rooms; in hazardous locations unless otherwise provided in the NEC®; and embedded in poured cement, concrete, or aggregate. There are additional limitations for Types NM and NMS cable. The reader is referred to this section of the NEC® for a complete list of locations where types NM, NMC, and NMS are not permitted.

 

[robby]

What you are considering an "outlet" is called a "receptacle" in the NEC. In NEC terms, an "outlet" is just a connection point. It is not limited to a plug-and-receptacle connection, as you might think. From the 2011 NEC (2017 similar):

I think 625.40, as discussed by @PV-EV above, is new to 2017. There is no 625.40 in 2011, and 625.40 in 2014 is completely different (circuit needs to be sized for continuous load). At quick glance, I don't see anything like this in NEC 2011 or 2014. So unless your community has adopted 2017, it's probably a non-issue. If you are on 2017, a subpanel with a dedicated breaker for each Wall Connector solves the problem.

2017 NEC 625.40 talks about outlets, not receptacles (see above), so it would apply to either a 14-50 or hardwired Wall Connector.

Wow, thank you for this correction. This is frustrating, as my electrician advised we go with two HPWCs rather than two UMCs for exactly this reason (he said the HPWCs wouldn't require separate wire runs all the way back to the panel, but 14-50s would). Sounds like he was mistaken. Maybe we aren't on NEC 2017 yet, but if that's the case, is there any reason why the 14-50s would require separate runs?

 

[miimura]

Wow, thank you for this correction. This is frustrating, as my electrician advised we go with two HPWCs rather than two UMCs for exactly this reason (he said the HPWCs wouldn't require separate wire runs all the way back to the panel, but 14-50s would). Sounds like he was mistaken. Maybe we aren't on NEC 2017 yet, but if that's the case, is there any reason why the 14-50s would require separate runs?

If you have a long run back to the main panel, you're better off putting in a sub-panel close to the outlets, whether those outlets feed receptacles or hard wired devices like Wall Connectors. Sub panels are much cheaper than I thought. A 125A 4-space sub panel and two 50A breakers is less than $50 in parts.

 

[tga]

Wow, thank you for this correction. This is frustrating, as my electrician advised we go with two HPWCs rather than two UMCs for exactly this reason (he said the HPWCs wouldn't require separate wire runs all the way back to the panel, but 14-50s would). Sounds like he was mistaken. Maybe we aren't on NEC 2017 yet, but if that's the case, is there any reason why the 14-50s would require separate runs?

There's been talk here in the past about multiple 240V outlets on a single circuit. The consensus was that there's nothing explicitly forbidding it, so you could install two 14-50's on a single circuit. But if you're subject to the 2017 NEC, it looks like 625.40 disallows it if the outlets were installed for the purpose of EV charging. In any case, I'd probably install a subpanel as @miimura suggested. I don't particularly like the idea of multiple high current 240V outlets sharing breakers, but that's just me.

 

[gilscales]

Sub panel parts are cheap and it is a better way to go but it is also a bit more work if the garage is detached as you have to provide an earth ground in the form of an 8ft. copper plated ground rod driven into the soil and a 4 ga. solid wire ground cable (armored if it is exposed) so they will charge extra for that, it is worth having a sub panel though as any future wiring can be added in the garage easily.

 

[DanInSunnyFL]

Hi all,
Thanks for the info, and sorry for not responding sooner. So 6-3 UF-B seems to be the way to go?

I have abandoned adding a receptacle. My new plan is to run the UF-B from the inside panel, up through it's chase, into the attic but then I'm not sure what I will do. The inside of the garage is drywall and there's probably an inch between the drywall and the concrete block. The top of the block is filled w/ concrete on the other garage so I'm guessing it is on this side as well. So, I'll need to bring the UF-B down through grey PVC conduit and then hopefully I can fish it behind the drywall and then poke a hole in the CB outside. Outside I'm thinking I'll add a flush mount box mount the HPWC on top of it.

My thinking is that having the plastic box would 1.) serve as a cable clamp and 2.) would also allow me to remove the HPWC and put a 14-50 receptacle (though I appreciate the advice on the 6-50) in if I sold the house or the HPWC broke down.

Do I cap off the neutral on both ends or just the box side? Any other thoughts?

Regards,
Dan

 

[davewill]

...
Do I cap off the neutral on both ends or just the box side? Any other thoughts?

Regards,
Dan

Sounds like a solid plan. I agree with running the neutral so you can use a 14-50 if you wish since it's a much more popular plug. Besides, you could conceivably want to plug an RV in some day. Go ahead and connect the white wire to the neutral bus in the panel. The only reason you're capping it at the box end is because there's no place to connect it in the wall connector. You might also consider having a junction box on the inside where you go through the CB wall just in case you ever decide you want to park and charge inside the garage instead.

 

[DanInSunnyFL]

No chance there will ever be an RV in my HOA

So, I met the electrical inspector and he was fine with NM 6/3. He was not concerned with the CB and said the department only requires UF if the wire runs outside of the house - down or through the CB is fine here. Since the only thing stick out of the house is the tail he said that was fine for the area. So, now to buy some wire and an old work box

Thanks,
Dan

 

[AWDtsla]

Does anyone have a list of all on-board chargers offered and their charging efficiencies? I know gen2 was better than gen1, then we had dual gen1 and dual gen2, then 48A, 48A software limited and 72A, then whatever the Model 3 has, and finally perhaps the current 48A only option on S/X is a 4th gen charger, or maybe not?

 

[israndy]

Model 3 has a 48 Amp charger too, seems like the new standard. Makes sense for residential installs. And with a shared destination charger you can take half of a 100 amp circuit.

 

[AWDtsla]

Model 3 has a 48 Amp charger too, seems like the new standard. Makes sense for residential installs. And with a shared destination charger you can take half of a 100 amp circuit.

Not if you have a 100 pack. Almost 10 hours 0-100? I've enjoyed 80A charging. Could I get by without it? Sure. I could also get by with a Honda Civic.

Wall Connector has load balancing built it, don't need the onboard charger to be limited at all. Provides nothing except frustration.