Almost Burned my House Down... Thoughts / Theories?

[mongo]

So my problem appears to be that I have ROMEX 6/2 running from my panel, thru my walls to my Tesla Wall Charger. ROMEX 6/2 is only rated for 55 amps. So running a continuous load at 48 amps exceeds the capacity.

Yep, common issue.

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[NotMyTruck]

So my problem appears to be that I have ROMEX 6/2 running from my panel, thru my walls to my Tesla Wall Charger. ROMEX 6/2 is only rated for 55 amps. So running a continuous load at 48 amps exceeds the capacity.
I also wouldn’t recommend you run this setup at 48amps. If you do have an issue - your cable won’t get got enough to trip the breaker. You have to run 50amps at 60amp breaker

That is not entirely true. Again. I wish I still had IEEE code access, Romex is only to be used for indoor installations. It should never be installed in conduit, however you can if you have (again I forgot what code quotes for expansion percentage). I hope someone with access can comment instead of googling shit.

Two. If your 6/2 Romex is on a single run, as in the only thing that cable and breaker serves is your car - you can go up to 55 amps on a 60 amp breaker using Romex 6/2. If that’s what your electrician did - that is totally fine. Your electrician is correct.

You also should run your setup at 48amps. That is exactly 80%.

In summary, Tesla installation guide is straight forward. You have these local electricians reinvent the wheel for no reason with custom cut offs and other shenanigans.

Edit: I need to do a better job with editing

 

[Carlos Thomas]

According to Grok:


Tesla’s Specifications: The Tesla Wall Connector installation manual specifies that for a 60-amp circuit delivering 48 amps, you should use 6 AWG copper wire rated at 90°C (e.g., THHN/THWN-2 in conduit, which is rated for 65–75 amps depending on conditions) or a larger conductor like 4 AWG NM-B (rated for 70 amps at 60°C). The manual explicitly recommends against using NM-B (Romex) for 48-amp charging unless it meets the 60-amp requirement, which 6/2 does not.


Safety Concerns: Using 6/2 Romex for a 48-amp continuous load risks overheating, as the wire’s 55-amp rating is too close to or below the required capacity. This could lead to insulation degradation, potential fire hazards, or tripped breakers. Some sources report that 6 AWG Romex has been used in practice but is considered non-compliant and risky for continuous 48-amp charging.


Recommendation: Do not use 6/2 Romex for 48-amp charging; it’s not code-compliant and could be unsafe. Use 6 AWG THHN in conduit and Consult a licensed electrician to confirm the setup and local & state code compliance.

 

[mongo]

That is not entirely true. Again. I wish I still had IEEE code access, Romex is only to be used for indoor installations. It should never be installed in conduit, however you can if you have (again I forgot what code quotes for expansion percentage). I hope someone with access can comment instead of googling shit.

Two. If your 6/2 Romex is on a single run, as in the only thing that cable and breaker serves is your car - you can go up to 55 amps on a 60 amp breaker using Romex 6/2. If that’s what your electrician did - that is totally fine. Your electrician is correct.

You also should run your setup at 48amps. That is exactly 80%.

In summary, Tesla installation guide is straight forward. You have these local electricians reinvent the wheel for no reason with custom cut offs and other shenanigans.

Edit: I need to do a better job with editing

You can upside the breaker if it's not a common size, but you cannot upside the load.
80% of 55A is 44A, that is the maximum allowable continuous load.

 

[NotMyTruck]

You can upside the breaker if it's not a common size, but you cannot upside the load.
80% of 55A is 44A, that is the maximum allowable continuous load.

Yes. I got a 50 amp breaker and charge at 40amps. But this Not OP’s situation.

 

[Trekboy]

That looks like a split bolt with copper wire and aluminum wire in direct contact. Your electrician is an idiot.

 

[Vegetaban]

Sorry tech term
Root cause analysis RCA
Wall Connector WC

too many acronyms

For what it’s worth, I knew your acronyms. But I do teach root cause analysis at a university for pharma lol

 

[HaulingAss]

This is why I do my own installs instead of hiring a "professional" electrician. Not only do I know I did it right, it's easier than going through the process of hiring someone else, checking their work and paying them. I take far more care to do a bulletproof install than someone who cares very little about your family and is mostly trying to bang out the job in record time and make a good living.

 

[CyberGus]

There is no issue using properly sized and terminated aluminum wire

That looks like a split bolt with copper wire and aluminum wire in direct contact. Your electrician is an idiot.

I guess “properly sized and terminated” is the real trick, eh?

But isn’t that what professionals are for? If I want it done improperly, I’ll save money and do it myself

 

[mongo]

Yes. I got a 50 amp breaker and charge at 40amps. But this Not OP’s situation.

I'm confused, they have 6 Gauge NM-B on a 60A breaker and were charging at 48. You were replying to:

So my problem appears to be that I have ROMEX 6/2 running from my panel, thru my walls to my Tesla Wall Charger. ROMEX 6/2 is only rated for 55 amps. So running a continuous load at 48 amps exceeds the capacity.

With:

Two. If your 6/2 Romex is on a single run, as in the only thing that cable and breaker serves is your car - you can go up to 55 amps on a 60 amp breaker using Romex 6/2. If that’s what your electrician did - that is totally fine. Your electrician is correct.

You also should run your setup at 48amps. That is exactly 80%.

48A is exactly 80% of 60, which is the breaker size, not the cable capacity.

 

[mongo]

So my problem appears to be that I have ROMEX 6/2 running from my panel, thru my walls to my Tesla Wall Charger. ROMEX 6/2 is only rated for 55 amps. So running a continuous load at 48 amps exceeds the capacity.

I don't think aluminum comes in NM-B/ Romex variants. Aluminum 6/6/6/6 SER does exist but is only good for 50 Amps (75C versus Copper at 60V). And would be paired with a 50A breaker.

For 48A charging, the cable would need to be 4/4/4/6 SER which is good for 65A at 75C.

The short run to the WC was 6/3 NM-B and undersized, but the thermal issue was likely due to the wrong split bolt being used to join the aluminum to the copper.

 

[Carlos Thomas]

I'm confused, they have 6 Gauge NM-B on a 60A breaker and were charging at 48. You were replying to:

With:

48A is exactly 80% of 60, which is the breaker size, not the cable capacity.

Talk me through what you are seeing and the chart you posted please?

 

[mongo]

Talk me through what you are seeing and the chart you posted please?

The chart is from the manufacturer of the short length of copper wire (Superslick Elite). Black outer sheath indicates 6 or 8 gauge. If it was 6/3+Ground, that is only rated for 55A. Applying the 80% continuous load derating, that means 44A max allowable charge current.

Regarding main panel to the disconnect:
Aluminum wire is less conductive, but service entrance (SE) uses the 75C column for current rating rather than the 60C that NM-B type does. Still, 48Amp charging reguire 60A capacity which would be #4 in Aluminum. If that is #6, it is undersized.

Your new setup uses individual THHN type wires to the WC which can handle 48A charging. It also uses Polaris instead of the wrong type of split bolt connector that was there, so that is good.

However, the disconnect box does not appear to be grounded. That's bad.

The white neutal line doesn't do anything, but having it not switched by the disconnect would be the normal prefered configuration (using the disconnect saved the cost of another Polaris connector).

 

[mongo]

@Carlos Thomas, did they check the second Wall Connector? If it has the same incorrect split bolts, it will fail in the future also.

 

[Carlos Thomas]

@Carlos Thomas, did they check the second Wall Connector? If it has the same incorrect split bolts, it will fail in the future also.

They changed out that one as well.

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