60A Breaker Trips in Daytime Vegas Heat Only

[DownshiftDre]

Great convo. We all wish we can get that piece of data of what would just a 60A breaker remove and replace do.

If it doesnt trip, could be a marginal breaker. If it does still trip, means either:

1. ambient temps around breaker driving derate or
2. size of conductor driving a derate.

Or combination.

All the 2 pole breakers are on top of panel. 2 A/C units, car charger and oven. Imagining its all generating heat to add to an already hot situation.

 

[dakhlkt22]

Curious if the temperature rating of wiring plays a factor too? This manufacturer says their NM-B wire should follow ampacity for 60C (140F).

Encore Wire Corporation

Our NM-B Wire building wire is permitted for 600-volt applications and is wiring of luminaries, devices and appliances.

www.encorewire.com

Looking at ampacity charts, wiring with better insulation is rated for higher amperages at a fixed temperature.

I have two electrical jobs going on right now, and I asked both electricians about temperature ratings for wiring, and one fully admitted he had no idea what I was asking about and said he never pays attention to temperature ratings for wiring. Not sure what that says about electrician field practices.

 

[Sophias_dad]

This manufacturer says their NM-B wire should follow ampacity for 60C

The NEC itself says ALL NM-B wiring should be following the 60C rating.

As a side note, the 90C rating is pretty much never usable in a residential setting. It requires that both the wire AND the endpoints be rated for 90C, and residential breakers are almost universally (if not all) rated only to 75C. The HPWC terminals are explicitly stated to be 75C.

 

[dakhlkt22]

The NEC itself says ALL NM-B wiring should be following the 60C rating.

As a side note, the 90C rating is pretty much never usable in a residential setting. It requires that both the wire AND the endpoints be rated for 90C, and residential breakers are almost universally (if not all) rated only to 75C. The HPWC terminals are explicitly stated to be 75C.

Interesting, and good to know. Wish my electrician had responded knowledgably like that.

 

[DownshiftDre]

Update-

With an open minded electrician, the circuit breaker was not replaced…for science and curiousity.

All wiring was changed out to 4AWG in conduit.

The neutral/ground wire that was mounted with a few strands and incorrectly snakes around the panel now correctly mounts to the ground busbar on the right side of panel cleanly.

While the weather has significantly cooled temporarily due to Hilary storm, plan to run extended charging hard in the daytime heat later in week.

If the results are inconclusive, more data capturing will then have to take place in Summer 2024.

 

[bradtem]

Do you technically need to decrease the breaker? If your TWC is set to max the pilot wave at 40a or even 44a, and your wire is rated for 55a, that should be a safe circuit. Yes, by the old rules of physical breaker and wires, you would not put wire rated for 55a on a 60a breaker, but for EVs where current is controlled by software on a hardwired circuit, it should be certifiable that no more than 44a will be drawn continuously (or ever) on that circuit, and thus your 6AWG is sufficient.

Or have the codes not gotten smart about software controlled current levels yet, and need a physical breaker.

Now I suspect if you are like most people, you have never encountered a situation where you needed to push 50a and 44 (or even 40) was not enough to get the charging you needed done. Most people greatly overestimate how much they need, they just want the most they can get. But in fact, many people do fine on Level 1, and it would be a very rare person who isn't fine with 24a of 240v level 2 except maybe on a model X, in a home. (Public chargers where people park for only a few minutes are the only ones who might notice a difference in being able to deliver >30a.)

Now, it is pretty cheap to put in a 50a breaker of course if you are up to doing that yourself, so little reason not to, but setting the TWC is free.

 

[DownshiftDre]

Update with upgraded 4AWG wiring setup without the breaker change.

Today the original breaker tripped again after about 45 mins of charging. It was a 101F (39C) day.

This means there remains two possible issues still:

1. Bad original 60A breaker that is right at the limit of 48A continuous charge. (80% continuous).

2. A 60A breaker in my panel needs to be derated for the current summer ambient conditions since it is above the 40C (104F) calibration rating within the elec panel with other high power breakers (i.e 2 HVAC Units) and heat buildup. Setting the car at 45A may be a solution for summer.

Anybody think there is a 3rd possible issue?

Breaker change with like for like 60A will follow soon and will see if can get any change in results.

 

[mongo]

Update with upgraded 4AWG wiring setup without the breaker change.

Today the original breaker tripped again after about 45 mins of charging. It was a 101F day.

This means there remains two possible issues still:

1. Bad original 60A breaker that is right at the limit of 48A continuous charge. (80% continuous).

2. A 60A breaker in my panel needs to be derated for the current summer ambient conditions since it is above the 40C (104F) calibration rating within the elec panel with other high power breakers (i.e 2 HVAC Units) and heat buildup. Setting the car at 45A may be a solution for summer.

Anybody think there is a 3rd possible issue?

Breaker change with like for like 60A will follow soon and will see if can get any change in results.

2.5 Adjacent breaker is running hot (lossy)

 

[DownshiftDre]

2.5 Adjacent breaker is running hot (lossy)

Interesting. As in need to check/tighten connections?

The 60A charger breaker is on right side row at very top. Direct to its left is AC#1. Under AC#1 is AC#2. Both 35A breakers.

 

[Cosmacelf]

Interesting. As in need to check/tighten connections?

The 60A charger breaker is on right side row at very top. Direct to its left is AC#1. Under AC#1 is AC#2. Both 35A breakers.

Yeah, the AC breakers are probably warm too, contributing to the heating issue. I don’t know why electricians as a matter of course don’t separate high amp breakers like that instead of putting them all together. Still, likely a new 60A breaker will fix. And if your wire lengths allow for it, I’d move a few breakers around…

 

[mongo]

Yeah, the AC breakers are probably warm too, contributing to the heating issue. I don’t know why electricians as a matter of course don’t separate high amp breakers like that instead of putting them all together. Still, likely a new 60A breaker will fix. And if your wire lengths allow for it, I’d move a few breakers around…

May be minimizing the amount of panel busbar the current passes through.

 

[Cosmacelf]

May be minimizing the amount of panel busbar the current passes through.

Yes, but why?

 

[mongo]

Yes, but why?

Reduces overall heat generation and voltage drop.
Even moreso if the feeder and branch circuits exit on the same side.

 

[Ed243]

Wonder if they are just calling it neutral when seeing white, since the white is likely being used for the second pole

If white is hot then it should be labeled at each connection. I usually see red tape.

 

[Ed243]

Could just be a weak breaker but it sounds like the whole installation is sketchy. Pay the $300. Have the job done right. Sleep well at night.

 

[davewill]

Could just be a weak breaker but it sounds like the whole installation is sketchy. Pay the $300. Have the job done right. Sleep well at night.

Dude already paid to have the install redone correctly. They just left the original breaker because they wanted to see if it was the problem. I'm not surprised that it was, as it was pretty obvious from the first post. The bad part of the install, using 6ga NM-B for 60a EV charging, has been repeated endlessly, since most of the electricians in America seem to do it, and they all seem to work.