14-30 charging

Fuma586 · Feb 4, 2016

I have a 14-30 outlet installed in my garage. I plugged my UMC in and forgot to Dial the charging draw down on the vehicle. It charged just fine at 40amps. Even charged at full speed of 28mph.

It got me wondering why the heck didn't it pop the 30amp circuit breaker that outlet is wired to. The UMC draws 40amps. I can view my household electrical use in real time via my "smart meter" and confirmed the charging did in fact draw the full 40Amps. Hmmmmm.

Everything I have read on this forum indicated that the breaker should pop if I don't dial down the charging amperage to about 24amps.

I think I have found the answer and I would like to vet it to the tesla community knowledge base.

The answer, I believe, lies in the fact that a 10-30 outlet is rated at 30amps PER POLE. Each wire and each breaker and each contact is rated for 30amps. Making it a 60amp outlet.

Can someone try and punch holes in this? I have done a lot of research and I am also an aircraft electrician by trade so I do have a firm grasp of electrical theory. It's just that my conclusion runs counter to every other thread I've found on this Forum.

Cottonwood · Feb 4, 2016

No, a 14-30 is a 30-Amp receptacle, and the 2-pole, 240-Volt breaker that should feed it is a 30 Amp breaker, feeding a 30-Amp circuit. While you can split the 30-Amp, 240-Volt circuit into 2, 30-Amp, 120-Volt circuits, it is still a 30 Amp circuit.

My best guess is that you have a bad breaker. Verify that it is in fact a 30-Amp breaker feeding the 14-30. If it is a 30-Amp breaker and is not tripping on 40 Amps continuous load, the breaker is defective and should be replaced. A defective breaker is a potential fire hazard.

Brass Guy · Feb 4, 2016

What Cottonwood said. At 240V, 40A on one pole is 40A on the other pole.
Your wires were probably getting hot. It warrants repeating: that is a fire hazard.

Fuma586 · Feb 4, 2016

It does use a 2 pole breaker. But each pole is 30 amps.

Fuma586 · Feb 4, 2016

Cottonwood said:
No, a 14-30 is a 30-Amp receptacle, and the 2-pole, 240-Volt breaker that should feed it is a 30 Amp breaker, feeding a 30-Amp circuit. While you can split the 30-Amp, 240-Volt circuit into 2, 30-Amp, 120-Volt circuits, it is still a 30 Amp circuit.

My best guess is that you have a bad breaker. Verify that it is in fact a 30-Amp breaker feeding the 14-30. If it is a 30-Amp breaker and is not tripping on 40 Amps continuous load, the breaker is defective and should be replaced. A defective breaker is a potential fire hazard.

It is a brand new 30amp breaker. Maybe it is defective out of the box.

Cottonwood · Feb 4, 2016

Fuma586 said:
It does use a 2 pole breaker. But each pole is 30 amps.

Exactly! That is the correct breaker to feed a 30-Amp, 240-Volt circuit.

If that is your breaker and it did not trip on a 40 Amp load, then replace the breaker ASAP; the breaker is faulty and a potential fire hazard.

- - - Updated - - -

Fuma586 said:
It is a brand new 30amp breaker. Maybe it is defective out of the box.

Something is wrong...

Fuma586 · Feb 4, 2016

Thanks for straightening me out Cottonwood. I'm buying a new breaker tonight on my drive home from work.

Chris TX · Feb 4, 2016

Fuma586 said:
I have a 14-30 outlet installed in my garage. I plugged my UMC in and forgot to Dial the charging draw down on the vehicle. It charged just fine at 40amps. Even charged at full speed of 28mph.

It got me wondering why the heck didn't it pop the 30amp circuit breaker that outlet is wired to. The UMC draws 40amps. I can view my household electrical use in real time via my "smart meter" and confirmed the charging did in fact draw the full 40Amps. Hmmmmm.

Everything I have read on this forum indicated that the breaker should pop if I don't dial down the charging amperage to about 24amps.

I think I have found the answer and I would like to vet it to the tesla community knowledge base.

The answer, I believe, lies in the fact that a 10-30 outlet is rated at 30amps PER POLE. Each wire and each breaker and each contact is rated for 30amps. Making it a 60amp outlet.

Can someone try and punch holes in this? I have done a lot of research and I am also an aircraft electrician by trade so I do have a firm grasp of electrical theory. It's just that my conclusion runs counter to every other thread I've found on this Forum.

Are you using the Tesla 14-30 adapter? If so, it automatically dials it down to 24A. If you're adapting the 14-50 to 14-30 and the breaker isn't flipping, it could be DOA or the Michigan winter is keeping the breaker cold enough to not pop. Cold breakers/wires take longer to build up heat.

Cyclone · Feb 4, 2016

Fuma586 said:
I have a 14-30 outlet installed in my garage. I plugged my UMC in and forgot to Dial the charging draw down on the vehicle. It charged just fine at 40amps. Even charged at full speed of 28mph.

I stopped right there. Something doesn't add up. Are you sure you don't have a 14-50 outlet, even if its wired to a 30-amp breaker?

Fuma586 · Feb 4, 2016

Chris TX said:
Are you using the Tesla 14-30 adapter? If so, it automatically dials it down to 24A. If you're adapting the 14-50 to 14-30 and the breaker isn't flipping, it could be DOA or the Michigan winter is keeping the breaker cold enough to not pop. Cold breakers/wires take longer to build up heat.

That's a good thought Chris. It was a very cold day when this happened and most of the wiring routes through the attic to an unheated attached garage.

I am using a non tesla adaptor to plug into the 14-30 so the car did not auto adjust.

Cyclone · Feb 4, 2016

Fuma586 said:
I am using a non tesla adaptor to plug into the 14-30 so the car did not auto adjust.

That makes more sense now. As Chris and other suggest, you probably got lucky because of the cold.

ernies · Feb 4, 2016

Fuma586 said:
It does use a 2 pole breaker. But each pole is 30 amps.

[My comment...each individual breaker connected to the bar is rated at 30 amps at 110-125 volts, not 220-250 volts. ]

Fuma586 · Feb 4, 2016

Update:

I replaced the suspect CB with a new 30amp and it still does not trip when drawing 40amp. Very strange.

GasKilla · Feb 4, 2016

Fuma586 said:
Update:

I replaced the suspect CB with a new 30amp and it still does not trip when drawing 40amp. Very strange.

you need to dial down the amp draw. It may "work fine" because your Tesla slowly ramps up the amp draw (as opposed to a motor that starts full load and would trip the breaker) so the breaker might not trip but your wire, breaker, connections etc will heat up and over time burn up the breaker and cause a fire hazard. Plus the long charge times of EVs makes this situation worse

Cosmacelf · Feb 4, 2016

Guys, breakers don't trip immediately when the current is a bit above its rating. It takes a while for heat to build up enough for a trip. In a cold environment, I could see a 30A breaker not tripping under a 40A load. Anyways don't make a habit of it since the wires could be heating up wood shavings or something.

Fuma586 · Feb 4, 2016

Cosmacelf said:
Guys, breakers don't trip immediately when the current is a bit above its rating. It takes a while for heat to build up enough for a trip. In a cold environment, I could see a 30A breaker not tripping under a 40A load. Anyways don't make a habit of it since the wires could be heating up wood shavings or something.

The UL standard permits a 30amp breaker to carry up to 40.2amps continuously.

This is the the answer to the entire thread. I appreciate everyone's concerns about me burning down my house but I have no intentions of pushing the limits of this outlet even if the UL Standards say it's safe.

Anyone have a tesla 14-30 adaptor for sale? PM me please.

Electricfan · Feb 4, 2016

Crap. I never get to the thread in time to answer when I know the answer!! I just recently read the answer to this one, but you got it too quick. But there was one detail you left out. The breaker will carry 135% of its rated load for two hours before tripping. If it didn't trip after 2 hours, then it is defective. At least that's what I read from one of the electrical smart guys who's a member on this forum. I'm just repeating what he said.

snort · Feb 4, 2016

Fuma586 said:
I am using a non tesla adaptor to plug into the 14-30 so the car did not auto adjust.

I'm curious what your connection was: My guess: Wall mount 14-30R. a non-tesla 14-30P connected to a 14-50R. Tesla 14-50P adapter plugged into UMC.

Something that /can/ work: Tesla 14-50P with the neutral leg removed. (it's not actually connected to anything). Or for that matter, a 14-50 extension cord with the neutral conductor removed from the plug end.

There are other routes you might have used too. (In my charger bag, I have a 14-50P with the neutral leg removed, connected to an L6-30R. Then I have an L6-30P that connects to a 10-30R. this will dial down the current to 24A automatically.)

The good news for Fuma is that once the car knows current should be dialed down for a location, it remembers it.

This sort of thing is exactly why I think we should insist upon having adapters from Tesla that dial down the current corresponding to what they're plugged into, and not rely on doing it in the car, and only use extensions and adapters that preserve this. About half the time when I plug into one of these situations for the first time, I'm exhausted from a very long drive. Just exactly when I'm most likely to be confused. Bring back the 14-30 and 10-30!!!

--Snortybartfast

Fuma586 · Feb 4, 2016

Bring back the 14-30!!!

FlasherZ · Feb 5, 2016

Fuma586 said:
The UL standard permits a 30amp breaker to carry up to 40.2amps continuously.

This is the the answer to the entire thread. I appreciate everyone's concerns about me burning down my house but I have no intentions of pushing the limits of this outlet even if the UL Standards say it's safe.

Anyone have a tesla 14-30 adaptor for sale? PM me please.

This is not true.

The UL standard requires that the breaker trip within 2 hours at 135% of its current rating. It does not permit it to carry 40 amps "continuously" (although it could up to 2 hours).

As noted, a 30A breaker will not trip at 30.00001A. Sometimes it will trip at 28A if in direct sun in a small pedestal, or 50A after a few minutes.

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