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

[mongo]

100 feet of aluminum wire: fifty bucks
100 feet of copper wire: hundred and fifty bucks
Setting your house on fire: priceless

The aluminum wasn't the problem. Copper can overheat a bad connection too.

Al 4/3 SER: $1.78/ ft
Cu THHN 6,6,10 (without neutral) would be $3.74/ft + conduit

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[REM]

It can't get hot though, that's the point. The only reason it got hot in this case is arcing. Here is what the AI calculated for a couple of examples :

4AWG copper @ 48A

Now 4AWG @ 48 Aluminum

I think the short copper run above was 6AWG, so just case another calculation

4AWG aluminum and 6AWG copper ended up giving the same result

 

[cybercricket]

The aluminum wasn't the problem. Copper can overheat a bad connection too.

Al 4/3 SER: $1.78/ ft
Cu THHN 6,6,10 (without neutral) would be $3.74/ft + conduit

Yeah, but as you point out the point of failure was the bolt... which wouldn't have been needed in the first place if they had a continuous run all the way to the Wall Connector... which you said they could have had, given it was a purpose-installed circuit during new construction. Even if the bolt was the correct type, a connection is a connection - potential failure point especially when human is factored in. So logically speaking CyberGus is correct.

 

[CyberGus]

So logically speaking CyberGus is correct.

I'm printing this and putting it on my wall

It all goes back to Mongo's caveat "when done correctly..." because I basically don't trust anyone to do it correctly. Or, if you prefer, I like to minimize the number of possible mistake vectors.

Paying extra for a continuous run of copper is cheap insurance against mistakes or malfeasance IMHO.

(To be fair, I didn't actually send a wire sample to the lab for verification lol)

 

[Mr Sir]

I am a retired union electrician and contractor from San Francisco. I would be called a master electrician by some. I was born into the trade and lucky enough to be trained additionally by "oldtimers".

This install has serious issues covered mostly here. Not all were mentioned even by me. Some issues missed are :

EVERY TIME ALUMINUM WIRE IS USED, IT MUST HAVE AN OXIDE INHIBITOR USED. BOTH ENDS OF WIRE.
EVERY TIME AL WIRE IS USED, IT MUST BE RE-TORKED AT REGULAR INTERVALS.

THERE NEVER WAS A RISK OF FIRE. THIS IS WHY ALL CONNECTIONS ARE IN METAL (FIRE PROOF) ENCLOSURES PER NATIONAL ELECTRICAL CODE.

 

[mongo]

I am a retired union electrician and contractor from San Francisco. I would be called a master electrician by some. I was born into the trade and lucky enough to be trained additionally by "oldtimers".

This install has serious issues covered mostly here. Not all were mentioned even by me. Some issues missed are :

EVERY TIME ALUMINUM WIRE IS USED, IT MUST HAVE AN OXIDE INHIBITOR USED. BOTH ENDS OF WIRE.
EVERY TIME AL WIRE IS USED, IT MUST BE RE-TORKED AT REGULAR INTERVALS.

THERE NEVER WAS A RISK OF FIRE. THIS IS WHY ALL CONNECTIONS ARE IN METAL (FIRE PROOF) ENCLOSURES PER NATIONAL ELECTRICAL CODE.

Retorquing is NOT recommended by manufacturers nor NEC.
The box wasn't metal, but metal can get hot enough to start fires(arc welder). The box melted and burning stuff was falling out of it.

 

[CyberGus]

I like the new micro smoke detectors and what is great they now have a 10 battery.

I like the idea, but I'd want a "smart home" detector. Depending on the configuration of your home, you might not hear an alarm blaring inside the garage.

 

[MIGUEL GONZALEZ DEL REY]

A SIDE NOTE: When the electrician installed my Tesla Wall Connector, he made a loop of extra wire coming from the panel before entering the wall connector. He stated that this was necessary for heat dissipation purposes. He said he had over 100 installations and does this with every one.

Making a loop???? this is the must stupid thing I have heard in a long time time. A loop of cable will contribute to heating is going to create a magnetic field increasing the impedance of the cable and hence the heating also longer cables means more loses.... I will go with the wright size of cable, cooper #6awg if the distance is under 100ft, and make shure all conectors are really tight, a loose conector can create a lot of heat.

 

[Mr Sir]

You are spot on. This is why there are State Electrician tests.
Spell check please so everyone here completely understands you, if you have it. ;-)

 

[Bridgeboy69]

Spell check please so everyone here completely understands you,

I understood what he meant even with the mispellings...they were close enough

 

[Mr Sir]

Making a loop???? this is the must stupid thing I have heard in a long time time. A loop of cable will contribute to heating is going to create a magnetic field increasing the impedance of the cable and hence the heating also longer cables means more loses.... I will go with the wright size of cable, cooper #6awg if the distance is under 100ft, and make shure all conectors are really tight, a loose conector can create a lot of heat.

No disrespect Sir! I only meant it as a communication assist.

 

[TickTock]

No disrespect Sir! I only meant it as a communication assist.

This thread inspired me to do an inspection. Two Tesla chargers daisy chained master-slave. Configured for 48A max. About 3 years of service with both chargers (another 5 years with just one). 60A breaker. There is some black gunk on the ground wire which appears to be left-over electrical tape residue - not oxidation). It does appear the feed on the bottom may have gotten hot enough to glass the outer surface of the insulation on the black wire but no signs of oxidation on the copper. Any code violations or other concerns?

 

[Aces-Truck]

This thread inspired me to do an inspection. Two Tesla chargers daisy chained master-slave. Configured for 48A max. About 3 years of service with both chargers (another 5 years with just one). 60A breaker. There is some black gunk on the ground wire which appears to be left-over electrical tape residue - not oxidation). It does appear the feed on the bottom may have gotten hot enough to glass the outer surface of the insulation on the black wire but no signs of oxidation on the copper. Any code violations or other concerns?

Did you re-torq the terminals, at 50 in-lb? If so, did the screws rotate, in order to again meet the torq spec?

 

[TickTock]

Did you re-torq the terminals, at 50 in-lb? If so, did the screws rotate, in order to again meet the torq spec?

No. I did pull on the wires to see if they were secure but that is all.

 

[mongo]

This thread inspired me to do an inspection. Two Tesla chargers daisy chained master-slave. Configured for 48A max. About 3 years of service with both chargers (another 5 years with just one). 60A breaker. There is some black gunk on the ground wire which appears to be left-over electrical tape residue - not oxidation). It does appear the feed on the bottom may have gotten hot enough to glass the outer surface of the insulation on the black wire but no signs of oxidation on the copper. Any code violations or other concerns?

Only the Universal Wall Connector has the double lugs for pass through

There should probably be a grommet or at least more sheathing

Edit :
Further, that is NM-B so needs to be 4 AWG, and the terminals have a max gauge of 4, so doubling up violates that spec also.

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