Why the breaker trips

[kwired]

They did make QO with aluminum bus. I believe they still do in smallest sizes

Those 1970's QO panels with the 100 amp main that spanned all the way across both sides of the panel were typically panels with aluminum bus. If there is a problem with them it often is burned bus to breaker failures. One of their mistakes with that product line. The six and 8 space load centers with horizontal bus are commonly sold with aluminum bus, but is also a catalog number for ones with copper bus, probably tin plated so won't be obvious just looking at it to tell the difference.

 

[EngineeredElectric]

I found a Seimens last week in a QO, I did not leave it.View attachment 2582081

Siemens makes breakers that are approved for use in QO panels

 

[jim dungar]

Those 1970's QO panels with the 100 amp main that spanned all the way across both sides of the panel were typically panels with aluminum bus.

That was the Q1 style breaker. But as that design was replace with the QO breaker the panels were also redesigned to use the new bolt-on QOM series.

 

[pipe_bender]

Those 1970's QO panels with the 100 amp main that spanned all the way across both sides of the panel were typically panels with aluminum bus. If there is a problem with them it often is burned bus to breaker failures. One of their mistakes with that product line. The six and 8 space load centers with horizontal bus are commonly sold with aluminum bus, but is also a catalog number for ones with copper bus, probably tin plated so won't be obvious just looking at it to tell the difference.

Here you'll see aluminum buss at the big box stores, no copper.
I can get copper buss for only a little more at my supply house. My boss thought he was buying the same panels for cheaper at the box store until we noticed its a AL buss.
After doing service work for a while now I will never install an aluminum bus panel again if I can help it. Seems you don't save very much especially compared to the labor.

 

[kwired]

Here you'll see aluminum buss at the big box stores, no copper.
I can get copper buss for only a little more at my supply house. My boss thought he was buying the same panels for cheaper at the box store until we noticed its a AL buss.
After doing service work for a while now I will never install an aluminum bus panel again if I can help it. Seems you don't save very much especially compared to the labor.

Both the aluminum and copper versions are tin plated bus. If you are lightly loading it there likely no real advantage either way.

 

[Sberry]

I am always curious when I use the same equipment without a problem and other guys cant seem to make it thru the week without finding a couple bad ones? I will haver to say this,,, a bigger issue is dry,,, so dry threads squeal and any moistuyre in the air clings to it first thing. Guy next to me has a panel corrode out and mine are st5ill fine, what is the difference? Probably some duct seal where the pipe came up and a whiz of spray inside it before we closed.