Advice on Wall Connector install

[SlowKnee]

So my electrician installed the following and I have few questions

• The install was done by a licensed electrician
• Tesla Wall Connector Gen 3
• Installed inside the garage right behind the main electric panel, so the wires length is around 2-3 feet
• 60amp breaker
• AWG 6
• All wires are inside the wall. No conduit since the charger is just on the opposite side of the main panel (Not exactly opposite, maybe a feet to the left)
• Currently I have commissioned it for 40amp since I see a lot of people here recommending AWG 4 for 48amp.

So question is : Can I charge at 48amp considering the short wire length or is it a substantial fire risk ? The licensed electrician was confident about the install and my lack of electric knowledge couldn't debate otherwise.

PS : I don't mind 40amp since I charge overnight but ever so often I need quick charge in middle of the day so would like to set it at 48amp if I safety can.

 

[UoMDeacon]

If your electrician knows what they are doing, then there's not delta in risk for 40A vs 48A. Does your city/town require permitting/inspection?
As for the charging rate - there's also no real life benefit to the battery between 40A and 48A.

 

[Cosmacelf]

If the electrician pulled 6 gauge wire inside a PVC or metal conduit or used MC cable (metal sheath), then it is to code for a 60A breaker. If he used NM-B (Romex) cable then it isn't to code for 60A breaker (48A draw). Romex is only rated for 55A instead of 60A (44A or 48A continuous load respectively).

However that rating is conservative since it takes into account the case where people will route it in a hot uninsulated 130 degree summer attic. Considering where yours is installed, I would have zero concerns running it at 48A unless your garage wall interior gets to 130 degrees in which case you've got other problems.

 

[jcanoe]

So question is : Can I charge at 48amp considering the short wire length or is it a substantial fire risk ? The licensed electrician was confident about the install and my lack of electric knowledge couldn't debate otherwise.

It is not only the wire gauge but also the type of wire/electrical cable that matters. 6 gauge nonmetallic B (NM-B) common trade name is Romex, is only rated for up to 55 amps. 6 gauge THHN wire is rated for up to 75 amps. THHN wire must be installed in either metal or plastic conduit. THHN wire is also used in metallic clad (MC) electrical cable.

If you electrician ran 6 gauge THHN in metal or flexible plastic conduit then you can safely set the Wall Connector for 60 amps and the Tesla Model Y will be able to charge at the 48 amp maximum for Level 2 charging. If the electrician installed 6 gauge NM-B then the circuit breaker should be changed to 50 amps; the Tesla Gen3 Wall Connector should be set for 50 amps and the Tesla Model Y will be able to charge at 40 amps.

 

[SlowKnee]

If the electrician pulled 6 gauge wire inside a PVC or metal conduit or used MC cable (metal sheath), then it is to code for a 60A breaker. If he used NM-B (Romex) cable then it isn't to code for 60A breaker (48A draw). Romex is only rated for 55A instead of 60A (44A or 48A continuous load respectively).

However that rating is conservative since it takes into account the case where people will route it in a hot uninsulated 130 degree summer attic. Considering where yours is installed, I would have zero concerns running it at 48A unless your garage wall interior gets to 130 degrees in which case you've got other problems.

Thanks for your insights ! But funny you say that since I live in Arizona and the non-air conditoned garage can go to 120 deg on few unfortunate hellish days.

 

[SlowKnee]

It is not only the wire gauge but also the type of wire/electrical cable that matters. 6 gauge nonmetallic B (NM-B) common trade name is Romex, is only rated for up to 55 amps. 6 gauge THHN wire is rated for up to 75 amps. THHN wire must be installed in either metal or plastic conduit. THHN wire is also used in metallic clad (MC) electrical cable.

If you electrician ran 6 gauge THHN in metal or flexible plastic conduit then you can safely set the Wall Connector for 60 amps and the Tesla Model Y will be able to charge at the 48 amp maximum for Level 2 charging. If the electrician installed 6 gauge NM-B then the circuit breaker should be changed to 50 amps; the Tesla Gen3 Wall Connector should be set for 50 amps and the Tesla Model Y will be able to charge at 40 amps.

I will check with the electrician on the type of wire he used. Thanks for the information. Quick follow-up, assuming he used Romex without PVC, would it be okay to set the connector at 50amp while the breaker is at 60amp since the max pull will never exceed 40amp from the connector

 

[jcanoe]

I will check with the electrician on the type of wire he used. Thanks for the information. Quick follow-up, assuming he used Romex without PVC, would it be okay to set the connector at 50amp while the breaker is at 60amp since the max pull will never exceed 40amp from the connector

In the short term this is not likely to cause any issue. To be code compliant the circuit breaker must not exceed the rating for the circuit. In addition to the breaker the type and gauge of wire used, receptacle or terminal block and installed electrical equipment define rating for the circuit.

It is OK to oversize the wiring (for future needs). It is never OK to under size the wiring for the circuit. The breaker value should match the label on the equipment (in this case the equipment supports different circuit configurations from 15 amps up to 60 amps.) Until the type of wire used has been confirmed assume the wire is only rated for 55 amps. Since the Gen3 Wall Connector does not have a setting for use with a 55 amp circuit use the next lowest setting, i.e. 50 amps.

This all assumes that the home's electrical service and service panel have the available capacity to add a 60 amp or 50 amp circuit. If the service or panel would not support a new 60 amp or 50 amp circuit you would probably be able to install a 40 amp or 30 amp circuit. The Gen3 Wall Connector can be configured for use on 40 amp and 30 amp circuits.

 

[davewill]

I will check with the electrician on the type of wire he used. Thanks for the information. Quick follow-up, assuming he used Romex without PVC, would it be okay to set the connector at 50amp while the breaker is at 60amp since the max pull will never exceed 40amp from the connector

Technically, that's to code, but better to use a 50a breaker. More protection and less confusion in the future with someone seeing the 60a breaker and assuming that they can set the wall connector for 60a.

 

[fiehlsport]

Plenty of people use romex and set their wall connectors to 48 amps, in cases where they shouldn't.

I always say they shouldn't, and am happy to say it's against code.

But man, in this case... 2-3 feet of romex has me leaning towards 48A and forget about it. It's not going to matter. It's worth noting that the electrician DID perform this job incorrectly though. As a licensed electrician, they should know better than to use romex and set it to 48A. But as a reasonable person, no, it's not going to make a difference.

 

[jcanoe]

Plenty of people use romex and set their wall connectors to 48 amps, in cases where they shouldn't.

I always say they shouldn't, and am happy to say it's against code.

But man, in this case... 2-3 feet of romex has me leaning towards 48A and forget about it. It's not going to matter. It's worth noting that the electrician DID perform this job incorrectly though. As a licensed electrician, they should know better than to use romex and set it to 48A. But as a reasonable person, no, it's not going to make a difference.

The length, unless a very long run, does not change anything. The wire will heat up more than if it was 6 gauge THHN in conduit or 4 gauge NM-B. Over time the expansion and contraction of the wire can loosen the connection at the breaker and at the Wall Connector. A loose connection would increase resistance at the wire termination creating additional overheating. The wire insulation could break down and create an electrical short. It is easy to correct by reducing the maximum amperage to 40 amps or else changing the wire and mitigating the risk of an electrical fire.

 

[fiehlsport]

The length, unless a very long run, does not change anything. The wire will heat up more than if it was 6 gauge THHN in conduit or 4 gauge NM-B. Over time the expansion and contraction of the wire can loosen the connection at the breaker and at the Wall Connector. A loose connection would increase resistance at the wire termination creating additional overheating. The wire insulation could break down and create an electrical short. It is easy to correct by reducing the maximum amperage to 40 amps or else changing the wire and mitigating the risk of an electrical fire.

Oh, I'm with you there. But an additional 8 amps isn't realistically going to cause any of this to happen. Saying an electrical fire is in the cards is waaaay overboard for Romex vs. Conduit on 3 feet of #6 wire. We're talking about a difference of a few degrees celsius here. Actual electricians are using #6 Romex all over the country (I see stories of this all the time, including this one) and problems aren't being reported. I wouldn't be surprised if older NEC code actually allowed for #6 Romex in this situation, and it was derated due to some oddball fringe-case circumstance.

With that said, I don't condone using it since it's wrong, but what's done is done, and it isn't causing issues in people's homes.

 

[BelugaWhale]

If the electrician pulled 6 gauge wire inside a PVC or metal conduit or used MC cable (metal sheath), then it is to code for a 60A breaker. If he used NM-B (Romex) cable then it isn't to code for 60A breaker (48A draw). Romex is only rated for 55A instead of 60A (44A or 48A continuous load respectively).

However that rating is conservative since it takes into account the case where people will route it in a hot uninsulated 130 degree summer attic. Considering where yours is installed, I would have zero concerns running it at 48A unless your garage wall interior gets to 130 degrees in which case you've got other problems.

Why concerned with my 6 guage wire choice and not his? Mine will never get to 130 degrees

 

[jcanoe]

Oh, I'm with you there. But an additional 8 amps isn't realistically going to cause any of this to happen. Saying an electrical fire is in the cards is waaaay overboard for Romex vs. Conduit on 3 feet of #6 wire. We're talking about a difference of a few degrees celsius here. Actual electricians are using #6 Romex all over the country (I see stories of this all the time, including this one) and problems aren't being reported. I wouldn't be surprised if older NEC code actually allowed for #6 Romex in this situation, and it was derated due to some oddball fringe-case circumstance.

With that said, I don't condone using it since it's wrong, but what's done is done, and it isn't causing issues in people's homes.

The issue is someone reads this example and wrongly assumes that it is OK to run 100+ feet of #6 NM-B for a 60 amp circuit (48 amp continuous load while charging an EV) run through an attic, in the southwestern US, in summer, etc.

 

[brkaus]

I would disagree about being “just a little bit more”. The heat generated is going to be a function of I^2. So around 40% more going from 40a to 48a.

Assuming my brain math isn’t totally out for lunch today.

 

[davewill]

Why concerned with my 6 guage wire choice and not his? Mine will never get to 130 degrees

Here's the whole thing in a nutshell.

1. 6/3 NM-B doesn't meet the spec for a 60a EV charging circuit for a Tesla Wall Connector.
2. Because of the way Tesla wrote their install instructions, and because for non-EV applications 6/3 NM-B works fine for most "60a" circuit applications, lots of professional electricians, even "Tesla certified" ones have been using it, anyway.
3. For the same reasons, some local inspectors have even been approving them.
4. We have yet to see anyone here reporting a significant problem from one of these installs.

If you want to go ahead with the install you've done, you now have all the information you need to make your own choice.

 

[SlowKnee]

Here's the whole thing in a nutshell.

1. 6/3 NM-B doesn't meet the spec for a 60a EV charging circuit for a Tesla Wall Connector.
2. Because of the way Tesla wrote their install instructions, and because for non-EV applications 6/3 NM-B works fine for most "60a" circuit applications, lots of professional electricians, even "Tesla certified" ones have been using it, anyway.
3. For the same reasons, some local inspectors have even been approving them.
4. We have yet to see anyone here reporting a significant problem from one of these installs.

If you want to go ahead with the install you've done, you now have all the information you need to make your own choice.

Thanks for summarizing. Lots of really detailed useful information in this thread.

For closure, I am setting it to 40amps just as a precaution as it doesn't have any significant impact on my charging situation right now, meanwhile the electrician agreed to replace it with #4 Romex allowing me run with 48amp later.


PS : For anyone near Phoenix, if you need a good electrician DM me and I'll give you his contact. Very amicable and agreed to replacing it without hesitation. Required a few iteration but in the end customer satisfaction at core.

 

[Cosmacelf]

Why concerned with my 6 guage wire choice and not his? Mine will never get to 130 degrees

Because, unless I got threads mixed up (very possible), your run is in an uninsulated attic which could indeed get to 130 degrees F in the summer, whereas the other guy was in a wall stud which won’t.

 

[ACRei]

May I please ask - in your installation, did you incorporate a whole home surge protector? I was curious if the Gen 3 Tesla Wall Connector already took care of that aspect (surge protection).

 

[Mrbrock]

Thanks for summarizing. Lots of really detailed useful information in this thread.

For closure, I am setting it to 40amps just as a precaution as it doesn't have any significant impact on my charging situation right now, meanwhile the electrician agreed to replace it with #4 Romex allowing me run with 48amp later.


PS : For anyone near Phoenix, if you need a good electrician DM me and I'll give you his contact. Very amicable and agreed to replacing it without hesitation. Required a few iteration but in the end customer satisfaction at core.

Are you setting to 40A or 50A? I believe commissioning to 40A is the circuit size so you will only get 32A charging. With your wiring you can commission for 50A (40A charging).

Is the electrician going to charge you for fixing his mistake (additional cost for larger wiring)? If so, it would be much easier to just swap to a 50A breaker and be done with this. The extra 2kw provided by 48A vs 40A charging is rarely going to be noticed for home charging (usually overnight). 0-100% at 9.6kw (40A) will take about 8 hours. 0-100% at 48A will shave an hour off the time. Realistically the increased cost isn't huge over 3 ft but a breaker swap would be quite simple.

 

[SlowKnee]

Are you setting to 40A or 50A? I believe commissioning to 40A is the circuit size so you will only get 32A charging. With your wiring you can commission for 50A (40A charging).

Is the electrician going to charge you for fixing his mistake (additional cost for larger wiring)? If so, it would be much easier to just swap to a 50A breaker and be done with this. The extra 2kw provided by 48A vs 40A charging is rarely going to be noticed for home charging (usually overnight). 0-100% at 9.6kw (40A) will take about 8 hours. 0-100% at 48A will shave an hour off the time. Realistically the increased cost isn't huge over 3 ft but a breaker swap would be quite simple.

I had commisioned it to 50A. Nonetheless the electrician did come back and replaced the wire with AWG#4 and changed the breaker to 60A for no additional charge. I have now commisioned it to 60A but might consider dialing back to 50A to reduce battery strain