Wire size for wall charger

[iluvmacs]

Yes it does apply. I have two and so do you. I found several pages that were discussing this, which were electricians talking about it for regular residential home wiring systems, which are split phase and have two "nominal voltage systems", 120V and 240V. Therefore the need to designate the different wires because you can have more than one hot phase that need to be identified in some way.


...if you mark one of them with tape or some such, which is mentioned in that code section.

I don't believe this to be true. 120V and 240V are two "nominal voltages" but not two "nominal voltage systems". Your (and my) split-phase 120/240 is one "voltage system". A 3-phase 120/208Y would be another system. A 3-phase delta 480V would be another system. Heck, if I had a second 120/240 service in my house, fed from another transformer, that would be another system*.

The operative word here is "system", not "voltage". There is clear need to identify different phases when they originate from different systems. There is not when they belong to the same system, except in certain circumstances (which I mentioned previously).

(* - however, in this case I wouldn't actually have to identify them differently thanks to the exception you so conveniently provided: "Different systems within the same premises that have the same system voltage class shall be permitted to use the same identification." Note this wording also provides logical support for my claims above.)

 

[bcre3306]

Just stating 6 AWG does not tell the whole story. 6 gauge NM-B is not sufficient for 60A circuit but 6 gauge THHN (typically installed in EMT (electrical conduit)) is sufficient for a 60A circuit.

Not trying to be rude but this is not true. 6/4 in general is only rated to 50amp service and it's also limited to distance but 4/4 is the requirement for 100amp service which would be applicable for a 60amp service. Clearly you could run 2 gauge lower for the ground but the point I'm trying to make is code needs to be followed and it varies, should be checked per district.

 

[jcanoe]

Exhibit A: Cerrowire Resources - Ampacity Charts

 

[bcre3306]

Exhibit A: Cerrowire Resources - Ampacity Charts

Again, you aren't taking into environments and distance. This is very generic chart.

 

[jcanoe]

Again, you aren't taking into environments and distance. This is very generic chart.

OK; THHN wire is rated for 90C (194F) should be adequate for attic installations. I have not seen a home installation discussed on TMC where the distance from the service panel or sub panel to the equipment or receptacle exceeded 100 feet. There have not been many TMC discussions of voltage drop. Is is a big concern?

 

[bcre3306]

OK; THHN wire is rated for 90C (194F) should be adequate for attic installations. I have not seen a home installation discussed on TMC where the distance from the service panel or sub panel to the equipment or receptacle exceeded 100 feet. There have not been many TMC discussions of voltage drop. Is is a big concern?

My detached garage is over 100ft from my service panel so you nailed it why I know this! ;-)

 

[MY-Y]

My detached garage is over 100ft from my service panel so you nailed it why I know this! ;-)

I had a 175 amp aluminum wire run to a subpanel in my garage. You might want to consider something like that. I have a pair of 42 amp heaters, which is very nice when working in there. They don't take long to warm up the air.

 

[tombo12354@gma]

I had a similar experience to others in this thread: hired a company to install a Wall Connector and their invoice said 60A circuit but the used NM-B with #6. Personally, I'm not too worried about 48A vs 40A, so I've just changed the settings in the Wall Connector to a 50A breaker so it only charges at 40A max. I need to change the breaker at some point (since they put in a 60A breaker) but with the Wall Charger limiting to 40A I'm not too worried about safety, just code compliance.

Since this thread seems to indicate this happens more then it should (since an electrician really shouldn't be undersized a conductor to a breaker) I wonder if some are interpreting the code differently. What are the criteria for a continuous load? Is it just a duration of hours or a load size? I'm not disputing the code, or saying it shouldn't be done right, just curious if there are ambiguities around EVs in the code.

 

[iluvmacs]

I had a similar experience to others in this thread: hired a company to install a Wall Connector and their invoice said 60A circuit but the used NM-B with #6. Personally, I'm not too worried about 48A vs 40A, so I've just changed the settings in the Wall Connector to a 50A breaker so it only charges at 40A max. I need to change the breaker at some point (since they put in a 60A breaker) but with the Wall Charger limiting to 40A I'm not too worried about safety, just code compliance.

Since this thread seems to indicate this happens more then it should (since an electrician really shouldn't be undersized a conductor to a breaker) I wonder if some are interpreting the code differently. What are the criteria for a continuous load? Is it just a duration of hours or a load size? I'm not disputing the code, or saying it shouldn't be done right, just curious if there are ambiguities around EVs in the code.

Yes, it is a very common issue. The main path to misinterpretation is as follows:
- #6 NM-B is rated to 55A.
- Code allows you to "round up" to the nearest breaker size if the one you need doesn't exist.
- 55A breakers are nonexistent or extremely rare. OK, so you can use a 60A breaker.
- Installer thinks "I used a 60A breaker, so we're all good here, set it to 60A"
--> Faulty logic. The circuit was designed for 55A (44A continuous). Just because you got to "round up" the breaker doesn't mean you get to also use the extra capacity that afforded you.

You can usually convince that person of their folly if you use a range of higher standard breaker sizes instead: "I have a 3100A rated wire, so I rounded up to the 4000A breaker... that means I can plan to draw 4000A on it now, right??"

Or maybe some installers just don't think 5A matters...

 

[Rocky_H]

What are the criteria for a continuous load? Is it just a duration of hours or a load size? I'm not disputing the code, or saying it shouldn't be done right, just curious if there are ambiguities around EVs in the code.

And regarding this question, continuous generally was defined by a number of hours. I think it was four or more hours (maybe three?). But they didn't want people gaming the system with EV charging, where people might "pinky promise" that they would only charge for three and a half hours at a time instead of four, or nonsense like that, so I think it was in the 2017 version of NEC, they took away that choice in the large section 625 that is all about EV charging. EV charging circuits are now ALWAYS defined as continuous loads. Period.

 

[c3nsored]

New to this, this 6 AWG THHN wire should handle the Wall Connector 3? It's rated for 75A max.

Southwire 100 ft. 6 White Stranded CU SIMpull THHN Wire 20494150 - The Home Depot

Southwire's THHN and THWN-2 is a multi-purpose building wire used in conduit and cable trays for service, feeders and branch circuits in commercial and industrial applications. It is also used as a conductor

www.homedepot.com

Does the white jacket color matter?

Southwire 100 ft. 6 Black Stranded CU SIMpull THHN Wire 20493350 - The Home Depot

Southwire's THHN and THWN-2 is a multi-purpose building wire used in conduit and cable trays for service, feeders and branch circuits in commercial and industrial applications. It is also used as a conductor

www.homedepot.com

This black color 6 AWH THHN only rated for 55A

 

[MY-Y]

New to this, this 6 AWG THHN wire should handle the Wall Connector 3? It's rated for 75A max.

Southwire 100 ft. 6 White Stranded CU SIMpull THHN Wire 20494150 - The Home Depot

Southwire's THHN and THWN-2 is a multi-purpose building wire used in conduit and cable trays for service, feeders and branch circuits in commercial and industrial applications. It is also used as a conductor

www.homedepot.com

Does the white jacket color matter?

Southwire 100 ft. 6 Black Stranded CU SIMpull THHN Wire 20493350 - The Home Depot

Southwire's THHN and THWN-2 is a multi-purpose building wire used in conduit and cable trays for service, feeders and branch circuits in commercial and industrial applications. It is also used as a conductor

www.homedepot.com

This black color 6 AWH THHN only rated for 55A

That's a 90C wire. It's rated for 75 amps. Home Depot's site is giving the ampacity for wet locations.

 

[jcanoe]

That's a 90C wire. It's rated for 75 amps. Home Depot's site is giving the ampacity for wet locations.

My understanding is that circuit breakers and terminal blocks used in residential wiring (including the terminal block inside the Tesla Gen3 Wall Connector) are only rated for a maximum of 75C.

 

[MY-Y]

My understanding is that circuit breakers and terminal blocks used in residential wiring (including the terminal block inside the Tesla Gen3 Wall Connector) are only rated for a maximum of 75C.

Good point. The good news is that the wire in this thread (6 ga THHN) is rates for 65A at 75C. Still good free or a 60 amp circuit.

 

[tjgMY]

Just a quick post on wire size.

When I was finishing my garage I ran 3/3AWG for a future EV charger as at the time Tesla was supporting 80Amp charging and required 3/3. I'm finally getting a Model Y this week and was getting worried it wouldn't fit into a Wall Connector Gen3 as many people said it wouldn't. If it didn't fit I would have used a junction box to step down and later could split for two chargers.

It took a bit of time but the 3/3 AWG did fit directly into the Wall Connector and everything is working perfectly.

Hope this helps someone in case they want to use a larger gauge to future proof for larger charger(CyberTruck??) or splitting into two.

 

[tjgMY]

Just a quick post on wire size.

When I was finishing my garage I ran 3/3AWG for a future EV charger as at the time Tesla was supporting 80Amp charging and required 3/3. I'm finally getting a Model Y this week and was getting worried it wouldn't fit into a Wall Connector Gen3 as many people said it wouldn't. If it didn't fit I would have used a junction box to step down and later could split for two chargers.

It took a bit of time but the 3/3 AWG did fit directly into the Wall Connector and everything is working perfectly.

Hope this helps someone in case they want to use a larger gauge to future proof for larger charger(CyberTruck??) or splitting into two.

To add the exact cable was NMD90, 3/3 gauge rated at 300V, 105 A.

I used the Red and Black for Line and White for Ground/Neutral. The bare ground was coiled at the bottom.

 

[iluvmacs]

To add the exact cable was NMD90, 3/3 gauge rated at 300V, 105 A.

I used the Red and Black for Line and White for Ground/Neutral. The bare ground was coiled at the bottom.

For what it's worth (i.e. other people following this), the terminal blocks are only rated for 4 AWG as the largest acceptable.

Also, you should have used the bare ground wire for ground connection, not the white wire.

 

[rjpjnk]

Also, you should have used the bare ground wire for ground connection, not the white wire.

I agree. Although it will work fine of course, it is very important to distinguish between ground and neutral. Someone might see the white wire and assume it is neutral. I'd swap it to use the bare wire for ground. Should be simple fix.

 

[roc-noc]

To add the exact cable was NMD90, 3/3 gauge rated at 300V, 105 A.

I used the Red and Black for Line and White for Ground/Neutral. The bare ground was coiled at the bottom.

There is no "ground/neutral" wire. Single phase 240v wiring in the US for the Gen 3 Wall Connector specifies 2 hots and a ground (no neutral). If you used the white for ground then you need to add some green electrical tape to both ends where it connects. Or else change to the bare wire as others have suggested. And if you connected to the neutral bus in the breaker box, move it to the ground bus. They really are different although they are bonded together somewhere in your service wiring.

 

[rjpjnk]

That's interesting. In my breaker box the neutrals and grounds are all tied to the same bus in no apparent order. White and bare intermixed.
Do some locations require physically separate busses?