One Tesla charging leg 20F hotter

[Donskipton]

My main 200amp breaker tripped yesterday. The housing of the breaker was 200F. One leg was hotter than the other by 10F.

I have a 200amp main12 yrs old, feeding a 100amp generator sub panel, then a 50amp breaker going to the Tesla v2 charger. I monitor my main panel with "Emporia Energy" and I never get over 156 amps, at the time of failure I was running around 80 amps.

After letting it cool down I charge the M3 at 40amp for 15 minutes and one leg of the 100amp breaker is 20F hotter and one leg of the 200 amp is 10F hotter. The 50amp sub panel breaker to the tesla charger is not hot. The other main load on the sub panel is a 40amp driving an hvac which runs intermit and is not hot. The connections are tight. I will replace the 100amp breaker today and monitor with short charge sessions. I have a new 200 amp main breaker on order from Amazon.

Any ideas? Thanks.

 

[user212_nr]

Sounds like you have some equipment failures (breaker, panel, etc). 93 C is too hot, so if nothing else tripped, there must have been something wrong in your panel.

 

[MN-MS100D]

Is your 200A main a backfed breaker? What is the manufacturer of the panel/breakers?

 

[jdcollins5]

Have an electrician check your wire connections for tightness. A loose connection will generate heat. A circuit breaker trips on heat.

 

[Donskipton]

Is your 200A main a backfed breaker? What is the manufacturer of the panel/breakers?

Cutler-Hammer BW2200. Gen is isolated with auto transfer switch. I thought at first it was the main and because it got so hot I will replace it. But the down stream 100amp was even hotter on one leg so I am wondering if the tesla charger is somehow imbalanced. But the 50amp to the telsa charge was not hot. I guess that could confirm the 100 amp may be bad.

Don

 

[eprosenx]

My main 200amp breaker tripped yesterday. The housing of the breaker was 200F. One leg was hotter than the other by 10F.

I have a 200amp main12 yrs old, feeding a 100amp generator sub panel, then a 50amp breaker going to the Tesla v2 charger. I monitor my main panel with "Emporia Energy" and I never get over 156 amps, at the time of failure I was running around 80 amps.

After letting it cool down I charge the M3 at 40amp for 15 minutes and one leg of the 100amp breaker is 20F hotter and one leg of the 200 amp is 10F hotter. The 50amp sub panel breaker to the tesla charger is not hot. The other main load on the sub panel is a 40amp driving an hvac which runs intermit and is not hot. The connections are tight. I will replace the 100amp breaker today and monitor with short charge sessions. I have a new 200 amp main breaker on order from Amazon.

Any ideas? Thanks.

You have a loose connection somewhere that is generating heat.

It could be at any connection point or even internal to the breaker.

So in a panel such as you describe it could be the connection from the Tesla wires to the breaker, internal to the breaker, from the breaker to the main bus, the main bus may have segments bolted together, it could be the connection to the main breaker from the bus, it could be internal to the main breaker, or it could be from the main incoming wires to the main breaker.

Try to isolate the heat and replace parts / tighten as necessary. You are on the right track. It happens.

Most residential stuff never sees a fraction of its rating and so if you run it somewhat near capacity you find latent defects. 158 amps is a lot for a 200a residential panel. (Not out of spec, but just more than most)

 

[user212_nr]

But the down stream 100amp was even hotter on one leg so I am wondering if the tesla charger is somehow imbalanced. But the 50amp to the telsa charge was not hot.

The Tesla charger can't be imbalanced. It has to draw equal power from both legs due to the voltages or whatever principle is responsible for that. If you have single-pole breakers on the 100A panel, they could cause an imbalance.

Get yourself a clamp mutimeter right away so that you don't need to wonder about this imbalance theory. The numbers don't add up, if you say your load was 80A off a 200A panel. 80A is a reasonable load for your 100A panel, but that isn't what tripped.

https://www.amazon.com/Multimeter-Auto-Ranging-Resistance-Capacitance-Temperature/dp/B07RMX2QGM

 

[MN-MS100D]

Can you tell me in general what types of loads your residence has? Your load is very high compared to "normal" residential loads.

P.S. If you buy a clamp-on meter, get one that specifically measures true RMS values. Not sure if that cheap amazon meter measures true RMS.

 

[Donskipton]

I pulled the 100 amp and the bus bar plastic was partly melted to one lug. Scraped it clean and reinstalled but same temp problem when I plugged the tesla back in. Called in an electrician and changing out the entire bus bar and main 200amp. Looks like it just started arcing for some reason and the higher loads concentrated on this part of the bus bar. I am around 4,300sf, pool, 2 main hvac, 1 back porch hvac, Houston, a Tesla for 2 yrs, with an Y on the way. I recommend taking your circuit breakers temperature every few months.

 

[MN-MS100D]

Good call. I'd like to see you use a panel with bolt-on breakers but I'm in the minority in the internet with that thought because it costs more.