Tesla to Upgrade Wall Adapters After Reports of Garage Fires - Bloomberg News

[jerry33]

Another mentioned practice that can be very dangerous, is unplugging a charger during a charge. This can damage connectors, charging system and injure the user. It can burn the connectors, it could send thousands of volts through the charging system, and could cause molten metal to be ejected. The arc also could cause a fire or explosion.

When you press the button on either the UMC or HWPC the charging stops before the connector unlock happens (LEDs turn light blue/white). No danger.

 

[scaesare]

However, if one unplugs the UMC head plug from the 14-50 (or similar) while a charge is in progress, the issue remains. Not that this is a Tesla issue, but the dangers the OP referred to still exist.

 

[jerry33]

However, if one unplugs the UMC head plug from the 14-50 (or similar) while a charge is in progress, the issue remains. Not that this is a Tesla issue, but the dangers the OP referred to still exist.

That's certainly true. You always unplug the car first.

 

[qwk]

However, if one unplugs the UMC head plug from the 14-50 (or similar) while a charge is in progress, the issue remains. Not that this is a Tesla issue, but the dangers the OP referred to still exist.

About the only way I can see this happening, is when someone that knows nothing about your car, tries to steal your UMC.

 

[scaesare]

About the only way I can see this happening, is when someone that knows nothing about your car, tries to steal your UMC.

With 10's (and soon to be 100's) of thousands of Teslas out there, it's a statistical certainty that even owners will try every combination of inadvisable actions.

 

[qwk]

With 10's (and soon to be 100's) of thousands of Teslas out there, it's a statistical certainty that even owners will try every combination inadvisable actions.

Unfortunately, you are probably right.

 

[xhawk101]

When you press the button on either the UMC or HWPC the charging stops before the connector unlock happens (LEDs turn light blue/white). No danger.

Rainbow is a troll

 

[roblab]

However, if one unplugs the UMC head plug from the 14-50 (or similar) while a charge is in progress, the issue remains. Not that this is a Tesla issue, but the dangers the OP referred to still exist.

How in the world have RVs been able to plug into 14-50 outlets for YEARS and not figured out how to kill themselves??

Of course it's a danger. Has the danger been calculated as to the risk of fire if you fill your car at a gas station? But who cares?

 

[NigelM]

Another mentioned practice that can be very dangerous, is unplugging a charger during a charge. This can damage connectors, charging system and injure the user. It can burn the connectors, it could send thousands of volts through the charging system, and could cause molten metal to be ejected. The arc also could cause a fire or explosion.

Nonsense. And certainly no more dangerous than unplugging your dryer while it's running.

 

[bonnie]

That's dangerous advice. A plug that is so hot that it burns a person, should not be used. It could still be dangerous at 60 amps. It is dangerous to use electrical equipment with known safety faults.

Another mentioned practice that can be very dangerous, is unplugging a charger during a charge. This can damage connectors, charging system and injure the user. It can burn the connectors, it could send thousands of volts through the charging system, and could cause molten metal to be ejected. The arc also could cause a fire or explosion.

I certainly would hope that Tesla would have been proactive on delivery of the vehicles by providing instructions advising against unsafe usage. IE Advising against using Chargers after connections have get excessively hot and/or connections that are burned. Advising against unplugging charge connections, while the charger is still charging.

I think it would be safer to hard wire HPWCs.

You should probably learn a little more about how the Tesla charging system works (and disengages) before posting slanderous things like this.

 

[Doug_G]

Nonsense. And certainly no more dangerous than unplugging your dryer while it's running.

He is referring to arc flash, which is basically an electrical explosion producing 5000 degrees temperature and spraying molten metal. This does exist, and it's the reason why higher power circuits are permanently wired instead of having plugs.

You are NOT going to get anywhere that level of arc flash by interrupting an operating 240V, 40A circuit. Heck even SHORTING the circuit to ground isn't going to create an arc large enough to cause personal injury. That is total nonsense. If there was such a danger the electrical code wouldn't permit NEMA 14-50 plugs to exist.

Here's some basic reading on the topic: Arc flash - Wikipedia, the free encyclopedia

 

[dsm363]

That's dangerous advice. A plug that is so hot that it burns a person, should not be used. It could still be dangerous at 60 amps. It is dangerous to use electrical equipment with known safety faults.

Another mentioned practice that can be very dangerous, is unplugging a charger during a charge. This can damage connectors, charging system and injure the user. It can burn the connectors, it could send thousands of volts through the charging system, and could cause molten metal to be ejected. The arc also could cause a fire or explosion.

I certainly would hope that Tesla would have been proactive on delivery of the vehicles by providing instructions advising against unsafe usage. IE Advising against using Chargers after connections have get excessively hot and/or connections that are burned. Advising against unplugging charge connections, while the charger is still charging.

I think it would be safer to hard wire HPWCs.

I think you may be onto something. I unplugged my car while charging and saw this

 

[FlasherZ]

He is referring to arc flash, which is basically an electrical explosion producing 5000 degrees temperature and spraying molten metal. This does exist, and it's the reason why higher power circuits are permanently wired instead of having plugs.

You are NOT going to get anywhere that level of arc flash by interrupting an operating 240V, 40A circuit. Heck even SHORTING the circuit to ground isn't going to create an arc large enough to cause personal injury. That is total nonsense. If there was such a danger the electrical code wouldn't permit NEMA 14-50 plugs to exist.

Here's some basic reading on the topic: Arc flash - Wikipedia, the free encyclopedia

True that an arc flash from a circuit supplied by a #6 or #8 conductor is highly unlikely to spray molten metal; however, it is indeed capable of personal injury under a short. I saw an electrician once short a #6 120V leg to ground when manipulating a spliced conductor within a metal junction box, and the box cut through the insulation. The resulting UV light from the arc blinded him for a few moments (and the flash was seen by a bystander 2 doors away). However, the biggest risk in those types of arc flashes are the human's reaction to them. He jerked his hand away at high speed and smacked it hard against the edge of a ceiling joist, severely bruising it.

However, a 14-50 receptacle is well designed. The receptacle's clasping prongs are deep within the receptacle, and unless you are purposely trying to arc the receptacle, it is not possible to sustain an arc that would become visible outside the 14-50 receptacle; you would break the arc distance-wise long before that arc flash would affect you. There is no truth to the argument that unplugging a 14-50 will create any damage to either the Tesla or the person doing so.

 

[Doug_G]

Okay, yes, the flash certainly might dazzle you, but as you say his injury was from an instinctive reaction to it, not the flash itself.

Agreed that it would be nearly impossible to be injured pulling a NEMA 14-50 out of the socket.

 

[brianstorms]

As long as you are not wearing a red shirt when you pull a live NEMA 14-50 adapter out of a wall plug while the car is charging, you should be okay. Otherwise, this happens, as the crew of the Enterprise found out:

 

[Rainbow]

You are NOT going to get anywhere that level of arc flash by interrupting an operating 240V, 40A circuit. Heck even SHORTING the circuit to ground isn't going to create an arc large enough to cause personal injury. That is total nonsense.

I was across the room when a florescent ballast shorted out. Was quite surprised how powerful it was. It blew through the sheet metal case of the ballast. Then blasted through another layer of sheet metal that covered the ballast. It sounded like a gunshot and an arc. Molten metal went several directions. The largest piece I found, was the size of a pea.

I know a guy that was checking wire size with a vernier caliper, but he forgot to shut off the power. It was only one leg of a 220 circuit so it was only 120 when he touched the caliper to ground. He got slag burns on his face and shirt. He might have been blinded by slag if it wasn't for his glasses.

I know a guy that was starting up an air compressor, but the compressor was frozen. He didn't want to throw the off switch because the belt was smoking and slinging molten rubber near the switch, so he pulled the plug. He got some minor burns from splattering metal about the size of grains of sand.

There is no truth to the argument that unplugging a 14-50 will create any damage to either the Tesla or the person doing so.

Don't be so sure that a hot disconnect couldn't hurt the electronics in the Tesla charger. Switching circuits around the electronics typically have a capacitor to dampen the collapsing fields in magnetic coils. Hot disconnects, typically don't have the protection of a capacitor. So an extremely high voltage can occur for a fraction of a second.

Take an audio transformer. Hold the output with your bare fingers, and scratch input leads on the terminals of a 9 V battery. Hold the leads of a solenoid with your bare fingers as you scratch the leads on the terminals of a 9 V battery. You should feel a higher voltage than 9 V. Scale that up a bit and you could have something that could do serious damage to electronics and people. A hot disconnect and bad connections that arc can do serious damage to electronics

 

[scaesare]

How in the world have RVs been able to plug into 14-50 outlets for YEARS and not figured out how to kill themselves??

Of course it's a danger. Has the danger been calculated as to the risk of fire if you fill your car at a gas station? But who cares?

I'll let the other posts that speak to the significance of the dangers address that. I'm merely pointing out that it is possible to unplug the outlet-side of the UMC while under full load, the protection offered by the car discontinuing charging before unlocking the charge-port previously mentioned only applies to one end of the UMC.

While the dangers are likely slight, I certainly wouldn't recommend unplugging any 240V/80A connections under full load if you can avoid it.

 

[NigelM]

I was across the room when a florescent ballast shorted out. Was quite surprised how powerful it was. It blew through the sheet metal case of the ballast. Then blasted through another layer of sheet metal that covered the ballast. It sounded like a gunshot and an arc. Molten metal went several directions. The largest piece I found, was the size of a pea.

And the relevance in comparison with a UMC would be?

I know a guy that was checking wire size with a vernier caliper, but he forgot to shut off the power. It was only one leg of a 220 circuit so it was only 120 when he touched the caliper to ground. He got slag burns on his face and shirt. He might have been blinded by slag if it wasn't for his glasses.

Darwin award #1. Checking live wires with a metal caliper and not shutting off the power.....

I know a guy that was starting up an air compressor, but the compressor was frozen. He didn't want to throw the off switch because the belt was smoking and slinging molten rubber near the switch, so he pulled the plug. He got some minor burns from splattering metal about the size of grains of sand.

Darwin award #2. Everyone knows that air expands when warmed so filling a frozen air compressor is asking for all sorts of problems...



P.S. Remind me never to stand anywhere near you and electrical equipment. ;-)

 

[Doug_G]

I was across the room when a florescent ballast shorted out. Was quite surprised how powerful it was. It blew through the sheet metal case of the ballast. Then blasted through another layer of sheet metal that covered the ballast. It sounded like a gunshot and an arc. Molten metal went several directions. The largest piece I found, was the size of a pea.

Ballast is a large inductor - that has energy storage. Different situation.

I shorted 110V directly to ground once. During a visit friend asked me to fix a minor home wiring problem for him, but he switched off the wrong breaker. I didn't have a meter so, being cautious I deliberately bridged the circuit with a screw driver. There was a modest flash and bang, a snap as the breaker flipped, and my screwdriver had a black mark on it. Okay, now we've got the right breaker. End of story. No flying slag, no blinding flash. But again, that is a short circuit, not breaking an active circuit.

In this case we are interrupting a 9.6 kW circuit, and the break is occurring inside a NEMA 14-50 socket. Significantly less power is involved than shorting the circuit. You'll get a little "pop" sound and that's about it.

 

[Chris TX]

I love reading threads like this. They make me feel glad that I did the THREE 14-50 outlets in two of my properties and one at my parents' house. The one at my parents' house had a ~20' run of 6-3 copper to a surface mount outlet. Pulling all 40A for an hour or so yielded a cold 6-3 wire, a slightly warm 50A breaker, and a warm UMC cable. If anyone is concerned about their 14-50 outlet, just shut the breaker off, pull out the 14-50 outlet, and inspect the connections. Torque them down! Those are huge lugs that can take quite a large amount of torque. 6GA Wire needs a lot of love