aluminum conductors

[electricalperson]

got a service call today. customers electric range didnt work. went downstairs and found myself a nice lovely FPE panel. i opened the panel and found the 2 pole breaker tripped. i also found very loose connections on the breaker so i tightened them down. i turn the breaker on and checked the breaker using the FOP method. all normal no problems there.

then iturned on the oven all burners and oven on broil and then checked amperage. all normal there. then i checked the conductors with a infared thermometer and they were hot!! soon after the breaker tripped so i take the conductors off of the terminals and noticed they were all scratched up and they had an impresson from superman tightening down the terminal.

it looks like someone taken linesmen pliers and twisted them around the conductor damaging it in the process. i cut off the bad end and stripped it properly and installed it on hte breaker and the heat went away. i believe the problem was those scratched up and damaged conductor ends. everyone agree? whats everyones opinion?

 

[bphgravity]

Yes. Terminations are likely the number cause of problems associated with aluminum.

 

[electricalperson]

so a scratched, damaged piece of aluminum even when the conductor is tightened down can still heat up and trip the breaker because thats what i believe was happening

 

[infinity]

so a scratched, damaged piece of aluminum even when the conductor is tightened down can still heat up and trip the breaker because thats what i believe was happening

I'm not understanding why that condition would trip the CB?

 

[electricalperson]

I'm not understanding why that condition would trip the CB?

the heat from a loose connection causes breakers to trip

 

[LarryFine]

i turn the breaker on and checked the breaker using the FOP method.

then i turned on the oven all burners and oven on broil and then checked amperage.

You missed the opportunity to repeat that FOP test under load.

 

[LarryFine]

I'm not understanding why that condition would trip the CB?

The heat is carried into the breaker by conduction (not electrical) and affects the overload (thermal) portion of the breaker mechanism.

 

[TOOL_5150]

The heat is carried into the breaker by conduction (not electrical) and affects the overload (thermal) portion of the breaker mechanism.

FPE has thermal overload protection? :-?

~Matt

 

[LarryFine]

FPE has thermal overload protection? :-?

Yeah, the more you overload them, the hotter they get.

For troubleshooting, you don't use a clamp-on ammeter, you use a thermometer.

 

[jrannis]

Yes. Terminations are likely the number cause of problems associated with aluminum.

Same thing with copper conductors. Second biggest problem with copper..........theft.

 

[electricalperson]

You missed the opportunity to repeat that FOP test under load.

normally i do test it underload. i might of just forgot to turn the oven on first that might be the reason why the FOP test didnt show anything wrong

 

[LarryFine]

normally i do test it underload. i might of just forgot to turn the oven on first that might be the reason why the FOP test didnt show anything wrong

That's all I was getting at.

 

[wallyworld]

FOP method??

 

[JohnJ0906]

FOP method??

Fall-of-potential

 

[electricalperson]

FOP method??

measure mv across a loaded breaker and depending on the millivolt reading tells you the contacts inside the breaker are worn or not. we use it to check breakers that seem to trip out of no where

 

[GilbeSpark]

measure mv across a loaded breaker and depending on the millivolt reading tells you the contacts inside the breaker are worn or not. we use it to check breakers that seem to trip out of no where

Without having expensive testing equiptment, how do you measure across the breaker if it's loaded? Wouldn't that mean that it's installed onto the buss?

 

[LarryFine]

Without having expensive testing equiptment, how do you measure across the breaker if it's loaded? Wouldn't that mean that it's installed onto the buss?

Yes. This is one of those situations where you have to test with the equipment energized and under load.

First of all, always start with the voltmeter's range set to the full voltage of the system, just in case you discover an open somwhere. Test every point, then reduce the voltage range. An auto-ranging meter is best.

 

[Doug S.]

Has any one else found this to be potentially flaky? (FOP) I know my 87 shows AC millivolt readings in the presence of fluorescent lighting, so I have a hard time trusting it. I've tried this type of reading and I can wiggle the leads and get the reading to change, with the leads firmly pressed into the lugs. Again leading to distrust.

Regards,
Doug S.