kwired
Electron manager
- Location
- NE Nebraska
Not with induction motors loads.
Breakers tripping - heat related???
- Thread starter Greg Swartz
- Start date
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
I would also be interested in hearing back on the fix or if you were able to narrow it down.
A power monitor installed on the service entrance conductor and on the EV charger circuit might help.
A EV chargers on a plug in connection has had multiple posts on here about heat issues. You could advise them to reduce the charging current on the App during the summer to avoid issues. I would say to about 50% of the circuit rating, so about ~20A. Or avoid charging during the day.
If you have checked everything that is reasonable, then I can only think of more niche reasons, like power quality (harmonics), reduced service entrance conductor / neutral conductor and small utility wires. The high heat is very odd. I have only seen that happen once before. I was investigating a 4000A gear and the B phase bus was melting. There was a loose bolt that the IR camera picked up to be +200°C. They tightened the bolt but the heat was still above ~150°C. The underground service entrance conductors were undersized and didn't have duct bank spacing. The transformer was overloaded during peaks (oil level was fine and voltage wasn't a problem). Now this is not entirely relevant to your case, but the utility's conductors or transformer being undersized can also impact the panel's ability to dissipate heat. Although for a overhead service, that is unlikely.
A power monitor installed on the service entrance conductor and on the EV charger circuit might help.
A EV chargers on a plug in connection has had multiple posts on here about heat issues. You could advise them to reduce the charging current on the App during the summer to avoid issues. I would say to about 50% of the circuit rating, so about ~20A. Or avoid charging during the day.
If you have checked everything that is reasonable, then I can only think of more niche reasons, like power quality (harmonics), reduced service entrance conductor / neutral conductor and small utility wires. The high heat is very odd. I have only seen that happen once before. I was investigating a 4000A gear and the B phase bus was melting. There was a loose bolt that the IR camera picked up to be +200°C. They tightened the bolt but the heat was still above ~150°C. The underground service entrance conductors were undersized and didn't have duct bank spacing. The transformer was overloaded during peaks (oil level was fine and voltage wasn't a problem). Now this is not entirely relevant to your case, but the utility's conductors or transformer being undersized can also impact the panel's ability to dissipate heat. Although for a overhead service, that is unlikely.
James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
It seems everybody has missed the obvious answer.
There's a very common misconception that circuit breakers trip with a certain amount of amperage. But that's not true
There's not an amp meter inside the breaker, it's basically like a thermometer in there.
The amps going through it cause heat.
That's why the ambient temperature is important. If the temperature around the breaker is too high, then you add more heat because of the amperage going through it, that breaker can trip before the prescribed number of amps
And if it's outside, you better believe it..
If you've ever worked loading trucks, or have you ever sat in a car with the windows up in the summertime, you know that inside of a metal cabinet the temperature can be 40 or 50° higher than what the air temperature is.
Considering that most breakers trip at around 140° it's not a stretch to think that if you have 110° weather and that main breaker is outside in a metal cabinet which is 40° hotter inside than what the air is outside, you're already at a trip point without any load
I've seen outdoor main breakers tripped with only 35 or 40 amps on them.
There's a very common misconception that circuit breakers trip with a certain amount of amperage. But that's not true
There's not an amp meter inside the breaker, it's basically like a thermometer in there.
The amps going through it cause heat.
That's why the ambient temperature is important. If the temperature around the breaker is too high, then you add more heat because of the amperage going through it, that breaker can trip before the prescribed number of amps
And if it's outside, you better believe it..
If you've ever worked loading trucks, or have you ever sat in a car with the windows up in the summertime, you know that inside of a metal cabinet the temperature can be 40 or 50° higher than what the air temperature is.
Considering that most breakers trip at around 140° it's not a stretch to think that if you have 110° weather and that main breaker is outside in a metal cabinet which is 40° hotter inside than what the air is outside, you're already at a trip point without any load
I've seen outdoor main breakers tripped with only 35 or 40 amps on them.
ptonsparky
Tom
- Occupation
- EC - retired
Break a breaker open. Consider it a sacrifice to gods of education . You should be able to identify what's what and how it works. Typical CB is about as uncomplicated as an Edison base fuse.
Magnetic trip for short circuit and ground fault, and thermal trip for overcurrent.Thermal magnetic...I wonder what that means?
