EV Tesla Chargers melting breakers

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Alexagyagos

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I talked to my old boss the other day giving me a warning not to install a Tesla Charger on any panels 150amp or less. I know they were having some problems with NEMA 15-50 and suggested is the "lifetime warranty" 14-50. She does a lot of Tesla chargers and finding they are melting the breakers and causing overheating issues and suggests upgrading panel to be factored in to bid / permit. Has anyone had any similar experiences?
 
I have seen this observation on several other sites, not electrician sites. I have seen pictures of melted receptacles, melted wires, and seriously discolored circuit breakers.

Might be some kind of operator error or installation flaw. Might be some kind of poor quality parts being used.

I suppose it's possible that there is some kind of compatibility issue with the current waveform going into the charger. You would have thought UL would have done a very serious check on that though before listing the charger.
 
Well, basically any charger nowadays is a big Switch Mode Power Supply so on a single phase service, it will have somewhat high harmonics, including 3rd order that on a 3 phase service would have cancelled each other out. Current harmonic distortion (demand distortion) increases a lot as you approach the size limits of the transformer feeding it, so it’s conceivable that if the utility transformer was marginal to begin with on a 150A service, adding a large non-linear load to it could cause a significant increase in voltage harmonic distortion which could then cause over heating of the breakers and bus bars. That heating effect may be higher than what normal sine wave current at the same level would cause, which could damage the breaker, bus connections or both, especially if any connections themselves were marginal.
 
Jraef said:
Well, basically any charger nowadays is a big Switch Mode Power Supply so on a single phase service, it will have somewhat high harmonics, including 3rd order that on a 3 phase service would have cancelled each other out. Current harmonic distortion (demand distortion) increases a lot as you approach the size limits of the transformer feeding it, so it’s conceivable that if the utility transformer was marginal to begin with on a 150A service, adding a large non-linear load to it could cause a significant increase in voltage harmonic distortion which could then cause over heating of the breakers and bus bars. That heating effect may be higher than what normal sine wave current at the same level would cause, which could damage the breaker, bus connections or both, especially if any connections themselves were marginal.
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wouldnt the neutral be the conductor that experiences overheating?
 
Yes, that too. But it doesn’t mean the line circuits don’t. I’ve done a lot of VFD work and when someone uses a VFD to give them 3 phase for a motor from a single phase service, I’ve seen this happen on a few occasions.

We don’t really know what kind of numbers game the utility will play with their service transformer sizing, especially on residential service drops. They assume the financial risk in terms of having to replace the transformer if it fries, but we (consumers) are not free from the consequences of their decisions.
 
She sent me some pictures
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Sent from my SM-F926U1 using Tapatalk
 
That looks like and old panel. Challenger? I bet that tesla breaker is the first time this thing has seen a (relative) high amp continuous load. I wonder if thats an AL bus before they started tin plating them and the breaker to bus connection had a bit of voltage drop across it.
 
Todd0x1 said:
That looks like and old panel. Challenger? I bet that tesla breaker is the first time this thing has seen a (relative) high amp continuous load. I wonder if thats an AL bus before they started tin plating them and the breaker to bus connection had a bit of voltage drop across it.
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I agree. Sounds like a panel that never had a breaker in that spot and after years of siting in the open air probably had some oxidation on the bus tabs. Even worse for an outside panel and near salt water coast. I have seen a number of melt down like this over the years.
 
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