Bad breaker or too much load?

[Rollie Meyers]

Alimonum wire has a much larger thermal expansion coefficient than copper. The resulting deforming of the wire during heating and shrinkage of the wire during cooling has been traced to many house fires. Quite a number of years ago in Alaska aluminum wiring was outlawed and I remember hearing the trend was speading nationwide but I have no idea how far or how fast it went.

As for me, I'd look hard at replacing the aluminum with copper, but YMMV.

Jim Neeley, EE

Aluminum alloy conductors are allowed by the NEC & if installed correctly is safe & reliable

[Matt Meiser]

Ok, I changed out the breaker and did some load tests this morning.

First the old breaker was a Siemens. The screws on the load side weren't what I'd call tight but weren't noticeably loose. The contacts on the line side are spread further apart than the new CH breaker, and I'd guess they weren't making the best contact.

Base load for the shop, including the lighting, computer, mini fridge, etc showed 20a on one leg, 0.5 on the other. I think I'll rearrange some things in the shop panel to move one of the lighting circuits to the other phase and balance that better. I then turned on the AC, cyclone, and jointer/planer and saw about 45a/35a so I'm really nowhere close, except that I didn't have any blast gates open and wasn't putting a load on the j/p. Still, seems like I would be well away from 100a.

[Paul McGaha]

Matt,

Yeah it does seem you're good load wise, Looks to be less than 50 amps on a 100 amp feeder and that should be great.

Hopefull you've got it fixed with changing out the breaker.

PHM

[Dan Hintz]

As for me, I'd look hard at replacing the aluminum with copper, but YMMV.

The vast majority of houses out there use aluminum feeders coming into the main panel... aluminum works just fine, you simply need to make sure the connections are rated appropriately. Copper everywhere else.

[Jim Neeley]

I did not say, nor did I intend to convey, that aluminum conductors are forbidden by the NEC.

Just in case anyone here is unaware, the NEC per se is not forced on any region in America nor does a new version being issued make it take effect in any area. These are concious choices by local jurisdictions. They can choose to accept a revision, accept it with revisions (usually stricter, sometimes with exemptions), or not accept it.

What I said is:

"Quite a number of years ago in Alaska aluminum wiring was outlawed and I remember hearing the trend was speading nationwide but I have no idea how far or how fast it went."

Alaska outlawed it due to a string of electrical fires and near misses whose root cause was tied to aluminum coming loose in the terminals due to the differing thermal expansion coefficient.

Alaska outlawing it, by definition, indicates it was done at the local (statewide) level. No state controls the NEC; it is an instrument of the National Fire Protection Association (NFPA). Technically, the NEC is known as NFPA70.

[Rob Russell]

Matt,

I think you said you were going to properly torque the connections when you replaced the breaker. That's important - something most folks don't do.

Rob

[Mark Ottenheimer]

If the breaker terminal is copper and connecting an aluminum conducted you must use no-ox or it will loosen up. I have seen heated main breakers because of bad connect from the aluminum service cable. A good practice is to check the main breaker lug every time you are in the panel if you have an aluminum service cable.

[Steven Wayne]

I work as a NETA certified electrical testing technician. In english that means I test electrical systems for a living. While it is true that molded case circuit breakers used in these types of panels do fail, the majority of the time this type of problem is caused by a poor connection. There are two acceptable methods to test this type of connection - a low-resistance ohmmeter (DLRO or ductor) or torque check. The DLRO injects current (usually 10, 100 or 200 amps) and then measures the millivolt drop across the connection. I have seen hundreds, if not thousands of connections that "look" good that would fail this test with current passing through them. Since you most likely don't have a DLRO, torque check the connections.

[Mike Henderson]

I had that exact problem with the main breaker coming into my house. The breaker would get hot and trip. I tracked it down to corrosion between the aluminum wires running from the meter to the breaker and the copper connections on the breaker. I pulled the meter (to turn off the power) and replaced the wires with copper. That fixed the problem permanently.

Mike

[Ken Fitzgerald]

While aluminum may meet specs, I won't have it in my home or shop.

While waiting for base housing to come available while stationed at NAS Meridian, MS I lived in a rented trailer house. The landlord was an excellent landlord. He was an E-6 in the US Navy too. Nice guy. In the evenings after the kids went to bed and the lights were turned low, you could watch the sparks from the aluminum wires attached to the outlets in the house. It was a constant chore for the owner and I to tighten connections.

6 months after we moved into base housing, the trailer burned to the ground due to an electrical fire. I don't do aluminum. My shop I built a few years ago....200 amp service....The utility company's aluminum feed ties to my copper pig tail just outside the mast to the meter box. Copper through out. Yup it's expensive. So is replacing everything due to a fire....insurance doesn't tyically cover everything.

Just my personal preference.