NEMA 14-50 charges perfectly...most of the time (but not always)

[harlanlimpert]

Here's a mystery I've not seen addressed: The NEMA 14-50 I recently had professionally installed in my garage has worked perfectly, until yesterday. When I went to recharge yesterday, it blew the 50 amp circuit breaker. I reset the circuit breaker and tried again -- six times. Each time it tripped. About six hours later I tried again and it worked perfectly, just as it had in previous weeks.

The 220V NEMA 14-50 line was professionally installed, and the fact that it works MOST of the time indicates that is not the problem. I've wondered if it might be a bad cable. (It's original equipment Tesla cable.) That seems unlikely. No apparently problems with the Tesla itself -- I had charged it at a Supercharger earlier that same day.

Any ideas?

Many thanks for any ideas.

Harlan

 

[jjrandorin]

There are a lot of people here with electrical knowledge here so hopefully someone will help you. With that being said, is it possible that you exceeded your homes electrical draw? Meaning... what else was running in your home at this time? How big is the service to your house?

If you had air conditioning running, washing clothes, using an electric oven then plugged in your car on a 100amp circuit, and the car was the last thing you plugged in, maybe there wasnt enough power?

 

[MN-MS100D]

1) Get your electrician out there to review his own work. Tighten connections. Look for heated terminals or other sloppy installation.
2) Have him read amp draw and voltage during a test charge.
3) With so many trips, the breaker should be replaced. It may be faulty, but unlikely.
4) Please tell us when it was installed, what he installed, what size wire, how long a run, type of feeder (in conduit, romex, overhead or underground). Pictures would be great to see.

If you don't do any of these things, please at least dial down the charge current because you have a problem that could be burn your house down if it's not fixed.

 

[harlanlimpert]

There are a lot of people here with electrical knowledge here so hopefully someone will help you. With that being said, is it possible that you exceeded your homes electrical draw? Meaning... what else was running in your home at this time? How big is the service to your house?

If you had air conditioning running, washing clothes, using an electric oven then plugged in your car on a 100amp circuit, and the car was the last thing you plugged in, maybe there wasnt enough power?

Interesting thought. The house is only 20 years old and has a 200 amp service, so I don't THINK that's it. But, I will watch to see of the A/C is on when the problem appears. That could be it. Thanks again.

 

[SSedan]

I would be checking connections or having the electrician do so. I once had a similar experience with a water heater and the connection at the breaker was loose.

 

[harlanlimpert]

1) Get your electrician out there to review his own work. Tighten connections. Look for heated terminals or other sloppy installation.
2) Have him read amp draw and voltage during a test charge.
3) With so many trips, the breaker should be replaced. It may be faulty, but unlikely.
4) Please tell us when it was installed, what he installed, what size wire, how long a run, type of feeder (in conduit, romex, overhead or underground). Pictures would be great to see.

If you don't do any of these things, please at least dial down the charge current because you have a problem that could be burn your house down if it's not fixed.

 

[harlanlimpert]

I just spoke with the electrician who installed my NEMA 14-50 charger. Here's what he says (I'm pretty sure I'm describing this exactly correctly):

Local codes required that he install a GFCI circuit breaker when he initially installed the NEMA 14-50. Tesla, however, says that GFCI breakers cannot be used to charge a Tesla. So the electrician will come out, at no charge, and install the regular circuit breaker. He says this is a common problem among other electric car chargers - Chevy Bolt, Jaguar and Audi.

It still is a mystery as to why it sometimes works and doesn't at other times.

 

[brkaus]

I had a bad breaker installed initially. New from the shelf, but it tripped frequently.

check if the breaker is getting hot when charging?

I agree with @MN-MS100D above

edit - yes, multiple gfci in series can cause problems. Modern ones are much better, but I still see it.

 

[harlanlimpert]

Thank you, MN-MS100D, for your response. I posted a separate post on what the electrician told me.

 

[srs5694]

FWIW, I had a breaker go bad on my electric dryer once, and it exhibited similar symptoms. I'd turn on the dryer and the breaker would immediately trip. I could always get the dryer going after a few tries, and sometimes it'd work the first time. The problem went away when I replaced the breaker. It's conceivable you're seeing the same thing, but with a defective breaker rather than one that was failing of (presumably) old age.

 

[harlanlimpert]

I appreciate this. Needless to say, circuit breakers are wonderful things as safety devices to prevent fires. But like all things in life, they can fail and/or be finicky.

 

[KenC]

I just spoke with the electrician who installed my NEMA 14-50 charger. Here's what he says (I'm pretty sure I'm describing this exactly correctly):

Local codes required that he install a GFCI circuit breaker when he initially installed the NEMA 14-50. Tesla, however, says that GFCI breakers cannot be used to charge a Tesla. So the electrician will come out, at no charge, and install the regular circuit breaker. He says this is a common problem among other electric car chargers - Chevy Bolt, Jaguar and Audi.

It still is a mystery as to why it sometimes works and doesn't at other times.

Yes, there have been threads on this happening. The UMC has a GFCI built-in, and two GFCIs in serial have caused random tripping.

 

[lolder]

It's not a problem with your house load. The GFI may be the problem. The 14-50 outlet should be a Byant or Hubbel type with double V type wire clamps, not flat plate Levitron types. The outlet box should never get as warm as the plug adapter to the UMC-2 gets. The # 6 wire connectors on the breaker and outlet should be really tight.

 

[davewill]

I just spoke with the electrician who installed my NEMA 14-50 charger. Here's what he says (I'm pretty sure I'm describing this exactly correctly):

Local codes required that he install a GFCI circuit breaker when he initially installed the NEMA 14-50. Tesla, however, says that GFCI breakers cannot be used to charge a Tesla. So the electrician will come out, at no charge, and install the regular circuit breaker. He says this is a common problem among other electric car chargers - Chevy Bolt, Jaguar and Audi.

It still is a mystery as to why it sometimes works and doesn't at other times.

This probably isn't a double GFI problem, exactly. When the mobile connector starts up, it tests the ground connection by shunting a small amount of current through it...just the kind of thing that a GFI is supposed to detect and prevent. Normally, it isn't enough to trip a GFI, but in your case, it's right on the edge and the GFI trips sometimes. Once you successfully get past the ground test, I bet everything works fine for the rest of the charging session. Putting in a standard breaker should work fine, it's also possible a different GFI breaker (or a different brand) would also work fine.

 

[timk225]

There's no such thing as a 220 volt 14-50. You have a 240 volt 14-50 like everyone else in America.

 

[lolder]

Sometimes it's 207 v. The 14-50 can supply either. My voltage is sometimes 251.

 

[hcdavis3]

UMC Charger has GFCI built in, per code.

 

[davewill]

UMC Charger has GFCI built in, per code.

I don't actually think there's any "code" requiring that. Most EVSE manufacturers have chosen to include that function, but there's nothing requiring them to, to the best of my knowledge.

I got a little carried away with the following explanation, but here it is anyway....

It turns out that including GFI in a modern EVSE is easy to do. The EVSE already has the ability to cut power to the plug, so all that is needed is to include current transformers on the hot legs, monitor them using the CPU already in the EVSE and cut power the handle if a current leak is detected. Therefore almost all EVSEs include GFI protection. Strictly speaking, EVSEs don't need GFI. The way J1772 protocol keeps people safe from shock is by not energizing the pins on the plug unless the plug is safely inserted in the car. This is done by having the car place a specific pulldown resistance value on the pilot line when the car is ready for power. However, that by itself might allow the plug to become energized accidentally by being dropped in a puddle or by someone poking at the pins with a paperclip by the cable being cut... To prevent this, the car includes a diode on the pilot line that causes the pulldown to only affect the positive swing of the pilot signal(State C below). The EVSE is supposed to check for this and refuse to energize the pins if the pulldown affects the negative swing as well (Red arrow below).

A few manufacturers believe that including GFI in their EVSE is sufficient protection from the admittedly very slight chance of accidental activation and shock, so do not perform the diode check, although I think that they should. This was a problem for LEAF owners because both the EVSE included with the LEAF, and the Aerovironment EVSE sold by Nissan (and installed at all the dealers) neglected the diode check. Unfortunately, a number of the first generation LEAFs had that diode blow, but in a closed state. Those cars would work fine on the EVSE in the car and the ones at the dealership, but would refuse to work on other EVSEs that properly implemented the protocol. Those people had a difficult time convincing their dealers and Nissan that the problem was the car, and not the specific EVSE the car failed to work with.

OpenEVSE SAE J1772 Theory of Operation : Support
Basics of SAE J1772 : Support

 

[harlanlimpert]

Final update on this issue: The electrician came out and replaced the GFI circuit breaker with a regular breaker and now it all works perfectly. Thanks for all those who posted responses.

 

[FrankQ]

So…..he broke the code ?