Gen 3 Wall Connector pulling 105 Amps?

[Bleedblue82]

Sorry, dramatic post title but couldn't resist...

I had a Gen3 wall charger installed last year - only thing on a 50A breaker, firmware set to limit charging to 40A, car set to 40A. Last week noticed a burning smell from the Romex. Electrician came out today and measured current at the breaker at 105A (explains the burning smell). We stepped car down to 30A and 20A - at 20A there's 43A coming thru the breaker.

I'm stumped here. More importantly, my electrician is at a complete loss after five hours examining the circuit. If the car's receiving 40A but there's 105A coming thru the line, where's the excess energy going? The wall charger isn't hot (and the car hasn't exploded), but general voltage drop doesn't seem to be an appropriate explanation.

What do I do next? Do I try a warranty claim with Tesla and get a new charging unit? Help and advice greatly appreciated.

 

[Big Earl]

Sorry, dramatic post title but couldn't resist...

I had a Gen3 wall charger installed last year - only thing on a 50A breaker, firmware set to limit charging to 40A, car set to 40A. Last week noticed a burning smell from the Romex. Electrician came out today and measured current at the breaker at 105A (explains the burning smell). We stepped car down to 30A and 20A - at 20A there's 43A coming thru the breaker.

I'm stumped here. More importantly, my electrician is at a complete loss after five hours examining the circuit. If the car's receiving 40A but there's 105A coming thru the line, where's the excess energy going? The wall charger isn't hot (and the car hasn't exploded), but general voltage drop doesn't seem to be an appropriate explanation.

What do I do next? Do I try a warranty claim with Tesla and get a new charging unit? Help and advice greatly appreciated.

Seems implausible. If there really are 105 amps flowing through a 50 amp breaker, why isn’t it tripping?

 

[Bleedblue82]

I had the same question for my electrician (reputable company that’s done work for me before). His response was - shrug, they don’t trip immediately. He also replaced the breaker and found the same overage.

Could his amp meter be wrong, sure. But the burning smell lends credence to something going awry.

I’m just really confused at this point so if the answer is “send another electrician out” that’s fine.

 

[SilverString]

Hmm. Curious how he measured the 105 amps. I am not an electrician but it seems a 50 amp breaker should pop right away on a 105 amp load - certainly before the wiring starts to smell. Maybe some of the electrician crowd here can chime in on this. But that aside it sounds like there is a partial short in your HPWC, especially if it just started after having worked previously.

 

[DerbyDave]

Call Tesla Home Charging Support team at 877-961-7652 during PDT business hours. Wall connector is guaranteed for 4 years, and they will remotely diagnose the issue. If needed, they will ship you a new wall connector

 

[vcor]

If you smell burning, something is likely burning! If you are still getting 40 amps charging, then it is not shorted. Is the wire aluminum? If so, it could be the connections have failed. The Tesla WC is designed only for copper wire (see manual page 4). Using aluminum wire will cause problems like this. Can't say about the 105 amps.

 

[Bleedblue82]

Copper wire, professionally installed by qualified and licensed electricians... and operating great for 9 months. no faults in the cable, nothing else on the circuit. I can't explain it. Beyond confused. Calling Tesla and seeing if they'll send a replacement just to eliminate that variable.

 

[beatle]

Where is the burning coming from? It's true that a breaker may not trip immediately, but it will trip before it melts itself. I suspect a loose terminal. They can fatigue from the heat cycles and loosen themselves, even if they were tightened down properly during installation. 9 months seems a little short though unless you're charging a lot.

I had a loose terminal melt my 14-50 receptacle on my gen1 UMC (no termperature sensor), and a few months later I tripped my breaker from excess heat. While the receptacle melted to the point that I smelled it, the breaker merely got hot. I retorqued the wires at the breaker and the temperature came down to normal levels.

 

[Bleedblue82]

I talked to Tesla as @DerbyDave kindly suggested - they think it's a ground fault (high temp at terminals). I coincidentally had a mobile tech out today and he thinks the unit's probably faulty given sudden failure, but I'm getting (another) electrician to come check the boxes for tesla so I can get it warrantied out. Talk about a PITA... my last wall charger went for three years without one single tiny modicum of issues...

 

[MP3Mike]

Most likely an installation fault. Something not quite torqued to spec. Depending on where it was replacing the breaker may have resolved the issue. (Assuming it was properly torqued.)

But it sounds like the electrician you had out either had a faulty meter or they didn't know how to use it properly. (Or were they measuring the entire house, and not just the Wall Charger?)

In any case the fault is likely wherever the smell was coming from...

 

[vcor]

Another good trick is while charging, use a thermal camera or even an infrared temperature gauge along where the wires run, WC, and the breakers. It should help identify where the problem is.

 

[Vines]

I would suspect the burning smell and the over-amperage to be connected issues. It sounds like somewhere there is a terminal that is bad and overheating but not to the point where it is tripping the breaker.

What size wire is it?

I might try a different charger or a different device like a NEMA 14-50 outlet temporarily to see if there is still this overamperage condition.

I suspect a hardware failure at the HPWC or one of the terminations. Does your electrician have a thermal camera? It would be worth a check.

Definitely don't charge while it smells like burning lol. Also see the IT curves of a typical 50A breaker. Depending on the quality and style, there can be a delay of a couple of minutes when pulling 100A from a 50A breaker. The problem connection might be intermittent.

 

[brkaus]

I'd think a 50a breaker would trip near instantly at 2x the rating, unless it's one of those old recalled ones. I'm not sure I trust the readings.

Also, try to charge at a different location? I'm not visualizing a way that the current would be way over and change w/ the car settings and be a problem in the WC.

 

[Bleedblue82]

Electrician swapped the breaker for a brand new one; that one didn't trip either even when the car was set to 40A and amp meter showed 105A. I am more and more convinced electrician's amp meter was wrong. Just thinking thru the math - excess 60A x 240V is a lot of heat to dissipate out into the ether, and the HPWC wasn't blazing hot or anything (normal warmth under operation).

Thermal camera is a genius idea. Burning smell shows up just north of the panel where the romex exits the box, but it's hard to pinpoint.

@Vines I've recently plugged into a supercharger, Level 2 chargers, and outlets. No issues. I can plug into an outlet but without an amp meter of my own I can't test the circuit. Car is not exhibiting any behavior (e.g. rapid battery percentage increase) that leads me to think it's actually pulling more amperage than it's telling me it is. any ideas on how I can run a good test?

thank you all for the helpful commentary. really appreciate this community - as a non-electrician with a very limited set of DIY skills, getting some of these ideas at least makes me better at dealing with the service pros who come out!

 

[brkaus]

My math, that's 380w per foot of wire if your WC is 20 ft away and the heat is distributed evenly.

 

[brkaus]

My math, that's 380w per foot of wire if your WC is 20 ft away and the heat is distributed evenly.

Actually, considering the two wires next to each other, that's 740w per foot.

 

[SilverString]

I'm betting the new HPWC solves the problem.

 

[dannycamps]

I'm having a similar issue. Gen 3 wall charger installed as only thing on 50A breaker and configured for 40A. Has worked relatively fine for a year. The past few days upon plugging in the car, it will trip the breaker after a random period of time. Sometimes in a few minutes, other times in a few hours.

The last time it tripped, I happened to be close by and went to reset the breaker and it was pretty hot to the touch. I just left it off and I am scheduling an electrician to come out to replace the breaker which will hopefully resolve the issue.

 

[brkaus]

I'm having a similar issue. Gen 3 wall charger installed as only thing on 50A breaker and configured for 40A. Has worked relatively fine for a year. The past few days upon plugging in the car, it will trip the breaker after a random period of time. Sometimes in a few minutes, other times in a few hours.

The last time it tripped, I happened to be close by and went to reset the breaker and it was pretty hot to the touch. I just left it off and I am scheduling an electrician to come out to replace the breaker which will hopefully resolve the issue.

my brand new install went through two breakers in two weeks. Got hot and tripped. 3rd was a charm and no issues since. The install was in 2017.

 

[zoomer0056]

Great video from Munro Live