Breaker thrown. I wonder what root source of problem was?

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EatsShootsandLeafs

Well-known member
Joined
Aug 24, 2012
Messages
716
I have:

50 amp breaker
60 amp-rated wiring
14-50 socket

I have attached an EVSE to the socket. The EVSE is rated at 40 amp continuous. I charge at either 3.3 kWh on one car, or 6.6 kWh on my Leaf (max charging rate on the 2020 Leaf SV).

Last night I had the Leaf plugged in and it was charging at 27 amps or whatever it does (I remember distinctly walking past and the car was blinking as it charged). However, this morning it had barely charged. Turns out the breaker was thrown. I put it back and now I'm charging my lower-charge car at 3.3 kWh.

Possible failure points:
  • Breaker
  • wire
  • socket
  • evse
  • leaf's charger

As for failure point...It can't be the wire (most likely not). It could be a bad breaker (breaker is a year old and only been in use past two months), but that seems unlikely it would trip at barely over half its rating.

A pro electrician installed the breaker and the wire, but I put the 14-50 socket in two months ago. I'm thinking even if I did a bad job and stressed the cabling on this it would either now be creating a complete short (and an instant breaker throw), or excessive heat or something, but nothing to actually throw the breaker...?

I can't imagine the leaf's onboard charger briefly asked for more than 50 amps and the EVSE should have rejected that anyway, right? Therefore I'm thinking the EVSE for some reason briefly pulled over 50 amps. Is that a safe bet?
 
Defective breakers are pretty common, and you don't hear much about them because they usually - but not always - fail by failing to trip. It isn't a GFCI breaker, is it?
 
The first step is to see if there is continuity between either line and ground. Next pull of the covers on the outlet and inspect what you can. Is it aluminum or copper wire? Since it happened after some time it could be those fat wires growing a little and making contact on a sharp edge.
 
It’s not a GFCI breaker.

The cable is aluminum.

I’ve run a couple more events and at 6.6 kWh rate it goes for about 30 (9% charge last time) min then trips. Surely this means there is good continuity and no catastrophic short or loss of circuit somewhere...?

I’ll check continuity... edit: done, but probably too stupid to know how. I know my multimeter is set to continuity mode as I was using it this week on an electric fence, and the electrodes when touched together confirm it. However, no combination of poles in the socket itself generate any apparent continuity. Since the charger works for a while I assume I’m just doing it incorrectly.
 
Is the receptacle rated for Al wiring? Did you use anti-oxidant paste on the wire ends when installing the receptacle? Are the wire connections tight?

I'd guess it's a faulty breaker but check all those things first. If it still keeps happening I'd call the electrician back since this will wear out the breaker in time and may not be 100% safe at the moment.
 
Working with Alu wiring is tricky.

Coward that I am, I would swap out the breaker for a new one and call in an electrician to reinstall the 14-50 receptacle.
 
I definitely didn’t use paste but I only installed receptacle three months ago. I definitely made it very tight. I had no idea a 14-50 receptacle had to be rated for that or not.

I don’t have an amp probe.

The electrician was not somebody I want back (was a “get the job done quick” sort of guy, which is why he never installed the 14-50 either—house was a new build and he wasn’t very detail oriented ), but I am thinking a breaker replacement may be the simplest thing to try. I found installing the 14-50 to be a huge pain due to the stiffness of the wire so in no hurry to redo that!

Here's a pic of breaker for what good this is. I do not see indication of paste, whereas the 200 AMP wiring into the breaker does have some paste.

For what it's worth I have the car charging right now for about 10 minutes and the red wire here is very mildly warm. The black, however, is very hot. In fact, right next to the breaker I can only touch it for around 10 seconds before it's just too hot to touch. As I get further from the breaker it cools down, so a ton of heat is hitting that black wire right at the breaker.

breaker.jpg
 
You said it’s wired with 60 amp rated aluminum wire? That’s unusual to use aluminum rather than copper and that’s some thick stuff.

Sounds like a defective breaker or a poor connection at the breaker.

Does the breaker get hot to touch? If so after it trips I would feel each of the 2 wires at the breaker. A poor high resistance contact at the breaker will heat up the wire and the breaker.

A poor contact on a breaker can really heat things up. This is an example of a 15 amp double pole breaker with high resistance where it connected to the panel backplane. This is from my sub panel.


JgKkR1wl.jpg
 
EatsShootsandLeafs said:
I definitely didn’t use paste but I only installed receptacle three months ago. I definitely made it very tight. I had no idea a 14-50 receptacle had to be rated for that or not.

I don’t have an amp probe.

The electrician was not somebody I want back (was a “get the job done quick” sort of guy, which is why he never installed the 14-50 either—house was a new build and he wasn’t very detail oriented ), but I am thinking a breaker replacement may be the simplest thing to try. I found installing the 14-50 to be a huge pain due to the stiffness of the wire so in no hurry to redo that!

Here's a pic of breaker for what good this is. I do not see indication of paste, whereas the 200 AMP wiring into the breaker does have some paste.

For what it's worth I have the car charging right now for about 10 minutes and the red wire here is very mildly warm. The black, however, is very hot. In fact, right next to the breaker I can only touch it for around 10 seconds before it's just too hot to touch. As I get further from the breaker it cools down, so a ton of heat is hitting that black wire right at the breaker.[]

breaker.jpg



HIGH RESISTANCE CONTACT AT BREAKER WHERE BLACK CONNECTS.

turn off power, remove and fully reseat the black wire and retorque the set screw.

If it still gets hot replace the breaker.
 
Just looking at the photo, the red wire looks well seated underneath the screw while the black wire does not.
 
The black wire has slipped part way out of the connector--if you look closely, you can see where the screw was tightened against the wire (about 1/4-inch from the screw). The loose connection is heating the thermal overcurrent element in the breaker and causing it to trip even though the current is normal. I am concerned about the wire size--it does not look large enough to be rated for 50 amperes. If you keep the aluminum wire, you will need to tighten the terminal screws periodically (at breaker and at receptacle) because aluminum expands and contracts with heating/cooling of the wire every charge cycle. Copper generally runs a little cooler and does not expand/contract as much as aluminum so connections are less likely to loosen over time.
 
EatsShootsandLeafs said:
I have attached an EVSE to the socket. The EVSE is rated at 40 amp continuous. I charge at either 3.3 kWh on one car, or 6.6 kWh on my Leaf (max charging rate on the 2020 Leaf SV).

Last night I had the Leaf plugged in and it was charging at 27 amps or whatever it does (I remember distinctly walking past and the car was blinking as it charged). However, this morning it had barely charged. Turns out the breaker was thrown. I put it back and now I'm charging my lower-charge car at 3.3 kWh.
Charging rate is measured in kW, not kWh.

If you charge at 3.3 kW * 1 hour --> 3.3 kWh came out of the wall. (Multiply the units and values.)
3.3 kW * 2 hours --> 6.6 kWh came out of the wall.
 
The black wire has slipped part way out of the connector--if you look closely, you can see where the screw was tightened against the wire (about 1/4-inch from the screw).

I see the same pattern (but more shallow) on the other wire. The electrician may have gripped them with linesman's pliers to strip them. I still can't tell by looking whether the black wire is in all the way or not.
 
I've had a similar problem with my OpenEVSE. One of the phases (L1 or L2) shows signs of overheating (extremely charred) at the spade connector on the outlet side to the EV connector. This resulted in heat buildup and shutdown of the EVSE eventually - which then locked up the J-1772 connection at the Leaf (don't understand why that happened - but theorizing the burnout of a voltage sensor wire at the charred spade connector sent an error signal). I'm going to replace the spade connector today and hopefully all will go back to proper operation.

I've had issues with a L6-30 cable/connections overheating on this 30 amp circuit (even at 24 amps). Is it possible that one of the phases was carrying a substantial amount of the power - back to ground - if the resistance was very high in the other phase? I might have the ground fault turned off on the EVSE due to solar "experiments" at another location? I'll check also when I get back to operation?

IMG_7642.JPG
 
What about the use of paste on the Al wires at the breaker end? Is that recommended? I've never replaced a breaker before.
 
Nubo said:
What about the use of paste on the Al wires at the breaker end? Is that recommended? I've never replaced a breaker before.

YouTube is your friend https://youtu.be/ta0CvuSGQgY

AL anti ox “paste” https://www.amazon.com/gp/product/B000BODU66?pf_rd_r=YHMJJNB1V9FY75X34M8K&pf_rd_p=5ae2c7f8-e0c6-4f35-9071-dc3240e894a8&pd_rd_r=c1e3fe3c-9029-4b01-b052-95ef56be3da8&pd_rd_w=uhHFV&pd_rd_wg=vabhq&ref_=pd_gw_unk. Not necessary but it will not hurt.

I highly suspect the issue may be just the wire was not completely inserted into the breaker properly and the hold down screw is not making good contact. That bad contact caused high resistance which caused the heat. Be aware that the screw may be difficult to unscrew due to heat damage. If that’s the case you may also need to replace the breaker.

It’s best to use a #2 Robertson square drive screwdriver rather than a flat blade driver to tighten and loosen that hold down screw. You can get better grip with the square drive driver. https://www.amazon.com/Channellock-R204a-Professional-Recess-Screwdriver/dp/B00XNBS1W2/

Good luck and let us know how you make out.
 
A few general comments:

If a breaker trips like that after an extended period of using the load, the most likely cause is what the further information revealed, a poor connection from wire to breaker, or breaker to bus bar, causing excessive heating.

How many times have you reset the tripped breaker and continued to use it? If a couple times, the breaker is likely OK to continue using, but if, say, 10 times, it should be replaced by a qualified person.

The conductor terminations at the breaker should be redone by a qualified person, with less exposed conductor (1/16" is good, 1/8" is probably OK), and torqued to the manufacturer's specification with a torque screwdriver. The ends of the conductor should be inspected for damage and possibly cut back. The busbars should be inspected for discoloration, although I would think that with the bad connection being at the breaker terminals, this is not so likely.

The use of NoAlOx paste is good practice but generally not required by the breaker manufacturer. Its use or absence would be unrelated to a problem that develops after only 3 months of use.

Cheers, Wayne
 
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