Wire size for wall charger

[DonaldBecker]

I am aware they aren’t required to determine compliance with code. You are paying for an opinion by someone who may or may not know what they are doing. But every electrical violation you find has to deal with violations of NEC code. Removing tamper proof violations is a code violation that an inspector might hit you on. Your little quote is about limiting the liability of the inspectors. They don’t have to, but they may.

To echo this, the home inspections I've read did include multiple issues that 'appeared to be' NEC violations. They also had a disclaimer that not all flaws had necessarily been identified, and that not everything identified was necessarily a code violation.

All of the inspections had boilerplate text about aluminum wiring. Most said that the construction date put it outside the period of concern. They usually included a statement that a cursory check had been made that branch wiring was copper.

Bottom line: home inspectors aren't required to check conformance with code, but they are expected to.

 

[ScoobyDoo82]

Did you even read the thread? We're talking about a 40a circuit to a 14-50, with a mobile adapter plugged into it. Maximum 32a charging, which the 40a circuit with #8 Romex is entirely adequate for. I should know, I've had an EVSE plugged into such a circuit, installed according to the manufacturer's instructions, for 10 years.

Nah.. I didn’t read the whole thread.. don’t have time for that nonsense

 

[Duc916]

I've got a question for the group. I just installed my Tesla Gen 3 Charger and had a question about the breaker.
I have a 100 amp breaker and 3 awg wire connected to my charger.
Question: is it okay (and will it pass inspection) with the above 100amp breaker with 3 awg wires?

I know the above is overkill, but its what I had so I used it. I recently moved my electrical panel and upgraded to 200 amp service. My electrician installed 3 awg wire between the two panels (old 100amp to the new 200 amp panel) while I rewired the new panel. I finished moving all the wires over to the new panel and had more than enough length of the 3 awg wire so I installed the charger to that. I had ordered a 60amp breaker and was going to install it, but it wont accept the large 3 awg wire, so now im wondering if I shouldnt bother and leave the 100amp breaker I currently have installed. Any advise?

Small sub panel with 2 seperate 50 or 60 amp breakers to charge 2 EV’s in the garage ? That’s what we did. But had 2 nema 14-50’s

 

[Justjim]

8 gauge is minimum. Use 6 gauge for less heating and better efficiency.

6 gauge is only warranted if the run is over 30m (100ft). Otherwise 8 is fine for 40A.

 

[Justjim]

T

Small sub panel with 2 seperate 50 or 60 amp breakers to charge 2 EV’s in the garage ? That’s what we did. But had 2 nema 14-50’s

The 3 awg is way over kill. Yes the problem is the diameter of the wire. The charger needs to be protected with 60A breaker. If there is a problem at the charger, a 100A breaker will let it fry. Ask your electrician if he is comfortable cutting some of the strands to make it fit both the breaker and the charger which will also only support 4awg. Personally, I would get 6awg and do it right. I just brought 55ft of it home. It only cost $280 plus tax. Sob....

 

[blulegend]

We have 2AWG for a 75ft run that goes to a Gen2 on a 100A circuit. Also have a new gen3 on a 60A and 6AWG. If we ever want to swap the gen2 out to a gen3 for load sharing, would a couple Polaris connectors work to downsize the 2AWG to 4AWG or 6AWG fit in the rear mounting plate of the gen3?

 

[ScoobyDoo82]

T

The 3 awg is way over kill. Yes the problem is the diameter of the wire. The charger needs to be protected with 60A breaker. If there is a problem at the charger, a 100A breaker will let it fry. Ask your electrician if he is comfortable cutting some of the strands to make it fit both the breaker and the charger which will also only support 4awg. Personally, I would get 6awg and do it right. I just brought 55ft of it home. It only cost $280 plus tax. Sob....

No electrician who is licensed and has anything to loose would ever “trim” a #3 wire to have less strands. This is the number one way to cause an arc condition and potential fire. That’s a huge no no. Guy just needs to re-wire with the proper size..

 

[ScoobyDoo82]

Small sub panel with 2 seperate 50 or 60 amp breakers to charge 2 EV’s in the garage ? That’s what we did. But had 2 nema 14-50’s

This is the most common practice and it makes sense. It costs money. People are always looking for the cheaper way.. lol

 

[Justjim]

T

Small sub panel with 2 seperate 50 or 60 amp breakers to charge 2 EV’s in the garage ? That’s what we did. But had 2 nema 14-50’s

The 3 awg is way over kill. Yes the problem is the diameter of the wire. The charger needs to be protected with 60A breaker. If the is a problem at the charger, a 100A breaker will let it fry. Ask your electrician if he is comfortable cutting some of the strands to make it fit both the breaker and the charger which will also only support 4awg. Personally, I would get 6awg and do it right. I just brought 55ft of it home. It only cost $280 plus tax. Sob....

We have 2AWG for a 75ft run that goes to a Gen2 on a 100A circuit. Also have a new gen3 on a 60A and 6AWG. If we ever want to swap the gen2 out to a gen3 for load sharing, would a couple Polaris connectors work to downsize the 2AWG to 4AWG or 6AWG fit in the rear mounting plate of the gen3?

Somebody suggested putting a small subpanel on the end of the 2awg and install 60A fuses for one or two chargers on 6/2 extensions. You do have a 60A breaker somewhere for your gen 2?

 

[blulegend]

Somebody suggested putting a small subpanel on the end of the 2awg and install 60A fuses for one or two chargers on 6/2 extensions. You do have a 60A breaker somewhere for your gen 2?

The gen2 is on a 100A circuit from the main outside panel which goes inside the garage to a 100A disconnect. Then the run goes up and over to the opposite side of the garage to the gen2, all with 2AWG. I don't want to add a subpanel there and also wouldn't even have room there on the side of the garage door. Also don't want to have to shorten the 2AWG in case I need the full length in the future to upsize a charger again. That's why I was thinking of stepping down to 4AWG or 6AWG using Polaris connectors if it would fit inside a gen3 back plate if we were to switch the gen2 for a gen3.

The new gen3 on a 60A is on its own circuit also from the main panel.

 

[stopcrazypp]

The gen2 is on a 100A circuit from the main outside panel which goes inside the garage to a 100A disconnect. Then the run goes up and over to the opposite side of the garage to the gen2, all with 2AWG. I don't want to add a subpanel there and also wouldn't even have room there on the side of the garage door. Also don't want to have to shorten the 2AWG in case I need the full length in the future to upsize a charger again. That's why I was thinking of stepping down to 4AWG or 6AWG using Polaris connectors if it would fit inside a gen3 back plate if we were to switch the gen2 for a gen3.

The new gen3 on a 60A is on its own circuit also from the main panel.

You can always do a junction box to do the splicing. It would take up much less space than a subpanel. Not sure if it would be code legal to do it inside the Gen 3 itself even if it has space.

 

[Lumpydog]

Glad I found this thread. I used 6/3 NM-B Romex for a 70 Ft run to my garage and put it on a 60 Amp Breaker... I just finished installation. I would have bought 4/3 Romex had I understood the limitation of Romex vs THHN/Conduit.

That being said, I'm not undoing the wiring - it took a few days, I can't recoup the cost of the Romex and I'd like to go ahead and use the setup. To keep it safe/to code, is it as simple as swapping the 60 Amp breaker for a 50 Amp breaker and setting the V3 Wall Charger to 40Amps? I wouldn't be upset at losing the 7 miles/hour of charging as I charge overnight and would get to the same fully (80%) charged state.

 

[jcanoe]

Glad I found this thread. I used 6/3 NM-B Romex for a 70 Ft run to my garage and put it on a 60 Amp Breaker... I just finished installation. I would have bought 4/3 Rolex had I understood the limitation of Romex vs THHN/Conduit.

That being said, I'm not undoing the wiring - it took a few days, I can't recoup the cost of the Romex and I'd like to go ahead and use the setup. To keep it safe/to code, is it as simple as swapping the 60 Amp breaker for a 50 Amp breaker and setting the V3 Wall Charger to 40Amps? I wouldn't be upset at losing the 7 miles/hour of charging as I charge overnight and would get to the same fully (80%) charge state.

Yes that is all provided the 6/3 NM-B is properly torqued. No issue once you swap out the 60A double pole breaker for a 50A breaker. You need to provision the Tesla Gen3 Wall Connector using your phone, the Wall Connector's local Wi-Fi connection for a 50A circuit. The Wall Connector will automatically limit charging to 40A.

 

[Lumpydog]

Yes that is all provided the 6/3 NM-B is properly torqued. No issue once you swap out the 60A double pole breaker for a 50A breaker. You need to provision the Tesla Gen3 Wall Connector using your phone, the Wall Connector's local Wi-Fi connection for a 50A circuit. The Wall Connector will automatically limit charging to 40A.

jcanoe - much appreciated. Yes, 6/3 NM-B is properly torqued to 50lbs. I initially provisioned the Tesla WC to a 60A breaker (48A charging) when I set it up. I take delivery of my new MYLR in two days - my first EV. I came to this forum to quadruple check my work - I was more concerned about the run length - 70 ft... only to find (in this thread) that Romex and a 60A breaker = no bueno. Cr@p

After reading this thread, I was initially ticked at myself for trusting many videos/posts/blogs that stated 6/3 wiring and a 60A breaker were the way to go and would get you to 48A charging - I missed (my mistake entirely) that there were different types of 6/3 applications - THHN/Conduit vs Romex vs MC, etc. BUT - as I retrace my steps... I'm not super broken up about where I ended up. 70 feet of 4/3 would have been more difficult to manage in my run/application. I needed to go into a wall from my basement and up to a crawl space - and then back down into a wall and then exit that wall cavity. The 6/3 wiring was hard enough to route without any abrupt bends in the wire - I wanted just nice radius bends to minimize resistance. I'm betting 4/3 would have been difficult if not impossible to get to where I wanted the charger.

Add to that - my use case: I will likely plug in and leave my Tesla charging overnight. Assuming I charge up to 80% like most - if I was charging from Zero (unrealistic worst case), the difference between 48A charging and 40A charging is 44mph vs 37mph. In my case - if I plugged in my Tesla at 8:00 pm at zero charge - it would finish charging at 2:00 AM (48A) vs a little after 3:00 AM (40A). Either way - I'm sound asleep and it won't matter. The reality is, I'll be charging from a much higher starting percentage than zero. My observation - rate of charge matters way less at home - than it does when road tripping (which is where super chargers shine). I'm interested to hear if others have use cases where you need the faster @ home charging (so I can plan/foresee).

What I really wanted was an easy-to-use wall charger that could be converted to an NEMA 14-50 plug if I wanted in the future. Would I have liked 48A charging? Yep. Will I miss the difference? Not sure yet. Maybe I got what I needed vs what I wanted...

 

[TBrownTX]

I have 4/3 Romex and a 60A breaker, and have my car set to charge at 24A. Why? It charges in plenty of time even set at 24A with my use case. If I need it to go faster, I can simply crank it up.

I lowered it to help keep the heat down, especially in the hot Texas summer. I'm not worried about it overheating per-se, but would prefer to extend the life of the components if possible.

 

[Art84]

What I really wanted was an easy-to-use wall charger that could be converted to an NEMA 14-50 plug if I wanted in the future. Would I have liked 48A charging? Yep. Will I miss the difference? Not sure yet. Maybe I got what I needed vs what I wanted...

Don't worry about that at all, you ll not miss that.
I have 48A setup, but charge at 32A to not create unnecessary heat stress to the wiring of my house. It's plenty!!
You did absolutely right thing changing your setup to 50A breaker!

 

[EVer Hopeful]

if I plugged in my Tesla at 8:00 pm at zero charge - it would finish charging at 2:00 AM (48A) vs a little after 3:00 AM (40A). Either way - I'm sound asleep and it won't matter

This I think is the most important and most overlooked part of charging

The lower the charge rate the easier it is on all the components, and like you said ... who really cares how long it takes if it's overnight?

 

[Lumpydog]

Looping back to thank you all again for all the insights in this thread - really generous of you all to patiently and painstakingly respond at length with laymen's terms/explanations. I ended up pulling the 60A breaker and put in a 50A breaker. I re-commissioned the Tesla V3WC to a 50A breaker (40A charge). Based on my charge needs, I may reduce that further. It's fun to say you can charge super fast at home - but I'm not sure I actually need to charge super fast at home. I'd rather avoid stressing my equipment in favor of a charge rate that still fully (80%) charges my Tesla within the timeframe I need. While at home - it's really not hard to accomplish that.

I pick up my MYLR tomorrow - I'll loop back here over time and try to pay it back.

 

[jcanoe]

Looping back to thank you all again for all the insights in this thread - really generous of you all to patiently and painstakingly respond at length with laymen's terms/explanations. I ended up pulling the 60A breaker and put in a 50A breaker. I re-commissioned the Tesla V3WC to a 50A breaker (40A charge). Based on my charge needs, I may reduce that further. It's fun to say you can charge super fast at home - but I'm not sure I actually need to charge super fast at home. I'd rather avoid stressing my equipment in favor of a charge rate that still fully (80%) charges my Tesla within the timeframe I need. While at home - it's really not hard to accomplish that.

I pick up my MYLR tomorrow - I'll loop back here over time and try to pay it back.

You can lower (but not raise) the charging amperage from the Wall Connector provisioned setting using the Charging screen or the Tesla app and the Tesla Model Y will usually remember the charging amperage for each location (Home, Work, Other) where you typically charge. (This only applies to Level 1/2 charging, does not apply to Supercharging or DC Fast Charging.)

 

[MY-Y]

Discussions suggesting a slower charge is better often pop up on this forum. Here are some thoughts.

Charging slower benefits:
1. Less heat (some efficiency in lower i^2*R losses)
2. Longevity of components. (I've seen no evidence of this impacting real world longevity with a Tesla system.)

Charging slower drawbacks:
1. The car stays powered on while charging, so the longer charge times waste this energy. I think this far outweighs #1 above.
2. The battery isn't warmed up as much before departure. A bigger deal in the winter.
3. Minor, but more time the HPWC contacts are closed which increases the lightning / surge damage risk to the car.
4. While rare for me, sometimes I need to top off quickly.
5. More time at a higher SoC when setting the charger to departure time. (It's got to start charging earlier.)

Personally, I charge my MY at 48 amps and my M3 at 32 amps. Why? They won't charge any faster than that.