Why did only one side of the breaker burn out?

I've had this happen before on a breaker that was feeding a 220V hot water heater, and also on another 220 breaker feeding a clothes dryer. Just replace the breaker.
Don't understand what was aluminum, the breaker terminal or the bar the breaker clips into. Aluminum was popular for a while for wiring, but is bad in the real world. You could also replace the outside breaker box.... Joel in Florida =3D=3D=3D=3D=3D=3D=3D

Replace the box, unless you want to lose another breaker. The resistance of connection on that side of the breaker went up enough that it got hot. Scrap the whole mess, unless you want a fire that could destroy your home. Is losing your life worth saving a couple hours?
As far as aluminum, there is nothing wrong with it, as long as the mating connector is suitable. It should have a protective coating like 'no-ox' to keep condensation of of the contact area.

Hi Joel, the lug that the breaker pushes into is aluminum. Copper wire runs from the main breaker box and fastens to that lug with a set screw. It's a dual breaker for 220; one lug is still good, the other is trash. That lug and the breaker both needed to be replaced. As I found out this morning after visiting five different shops, replacing the breaker was easy; the lug was impossible (too old).
One guy suggested pulling the 'guts' from a new box and installing it in the old one. No thanks. Resigned myself to several hours* w/o electricity this weekend while I replace the entire box with a SquareD box n breaker.
Thanks -- Terry *If I was smart 'n everything, I'd probably be able to do the job in 30 minutes. Learned long ago that I'm not that smart and I'll always underestimate the time for the job, especially when I've never done it before... And I'll make at least three more trips to the electrical shop on Saturday, probably...

I don't follow what burnt, but a common issue is:
Bad connection->heat->thermal creep makes screw loosen ->worse connection->more heat->breaker fails and/or fire.
Some commercial insurers require thermograms of the breaker panels annually. You should consider torquing down the connections every year or so.

I'm a little confused why you'll be out power so long...
You say the breaker is in it's own box, so kill power and open the box feeding this one, disconnect the feeder at the source, tape off the exposed ends and tie out of harms way, re-energise the system, now you have a dead feeder in the separate box and can do all your work while the rest of the house has power, once the fix is done, turn off the house and tie the feeder back in.
Stuart

If you don't have any empty space you can put in a couple split breakers to get the the correct amperages and voltages in place of a couple good breakers, it's actually called duplex circuit breaker (or "half-size branch circuit breaker"). They have them at Home Depot. You get two poles in the space of one standard breaker but they're the same side of the power so you need two side by side to get both sides of the 220. You can get different amperages on each duplex breaker so you can match the breakers your replacing and the old 30 amp 220. So you replace the good 30 breaker with one duplex and then the one beside it with a 30 amp and what ever that breaker is duplex. Here's a picture: We use these all the time when the box is full and we need a new circuit.
Karl

I think you already got enough replies, but here's my comment the your first question: Nothing "shorted out". The connection point actually "opened up". A "short" or "short circuit" occurs when two conductors that are at different potentials come into contact with eachother-- as in the wires in a extension cord get rubbed together for a long time and finally the "hot" and the neutral touch. The resistance between the "aluminum lugs" and the tabs on the circuit breaker must be very low for the connection to pass, essentially, all the current in the circuit. If this resistance is VERY low, then the voltage drop across the connection will be very low and then the POWER (heat) disspated at that connection will be very low, too. In your case, all that needed to happen is that any little bit of corrosion at the point where the two parts touch, or any little bit of crud that might have gotten into the connection back when it was assembled, caused the resistance at the junction to increase, causing heat to generated there. The more heat, the faster the corrosion occurs,etc,etc, to failure. I tell you this in answer to your question--- either connection could do this independently of the other one.
Pete Stanaitis -------------------
Terry wrote:

Thanks to everyone for the comments.
Stuart... I toldya I wasn't smart. :-) Special thanks, your solution simply hadn't occurred to me. (I tend to be leery of electrons. Couple years back, I removed a fuse from a circuit to work on it. Happily, the line touched a ground inadvertently. BIG blue-white spark two feet from my face. There was a burn trace in the box that I hadn't noticed, it provided a conductive path. Whole new box installed by professional electrician) Anyway, disconnecting at the mains should be fine.
For "what's burnt": when you push a breaker in place, it makes a connection at the top, where an aluminum (?) tab sticks out from the box. That tab is hot. That tab is now burned off and/or corroded away. Which explains why I can't use a dual skinny breaker. I need both sides of the line to get 220V, and one side is burnt off in the box; there's nothing for the breaker to connect to the line. If I could install a new tab... I'd do it. But the tab is not to be found.
Thanks again, all -- Terry

The Gould ITE box is junk. Was junk on the day it was installed. Finding an old box with more buss is not the way to go.
What Stewart said about making the feeder dead, work away with the house power on.
While you are at it: how about thinking about doing the base work for a proper feed to the garage? Don't need to install the wire now, just leave the appropriate space for it.
Terry wrote:

Gould and ITE were bought out by Siemens. If you want the easiest replacement where the dimensions and physical layout of the knockouts match, get a Murray or Siemens sub-panel.
A) The aluminum buss in the breaker panel went bad, and that killed the breaker stab where it plugs in.
B) It's newer technology, driven by price to the end user - you can't let the competition sell their breaker panel for a buck less, they'll take all your sales. The 'builder model' panels have tin- plated aluminum busses to save a buck over using copper busses, and for the average use in a nice dry location they work just fine for 30 to 50 years - that is, till the tin plating wears through from breaker changes or is otherwise broken, thin plating on an edge with a burr can do it.
The aluminum oxide 'corrosion' eats it's way under the tin plate and the connection goes bad - aluminum oxide is an insulator...
C) You aren't going to get a new terminal - the catalog and the label on the door says they sell replacement interiors for panels. But the reality is you can special order it, wait weeks for them to make and ship it, and pay double the cost of a new panel.
If your old steel can isn't rusted and they still make that brand of breaker (not an orphan like Zinsco or Federal Pacific) and that model of panel (or something close) you can buy one and do a "Gut Swap" - mount the new interior in your old can, and save the trouble of physically swapping the steel box...
But the legalities of a Gut Swap are a bit murky, so it's not the first choice - and NOT for the DIY-er!! You usually have to modify pieces and drill new mounting holes, and it has to be thought through from both the mechanical and electrical angles, insulation sysrtems, . Otherwise the whole thing shorts out when you reenergize it, and there is going to be some 'splainin' to do.
(This is normally used on large interior panels flush-mounted in the wall with a dozen or more conduits leaving, where it would be a two or three day gold-plated bastard of a job to swap the steel can - and the residents can't be off for three days, so you have to rig up temporary power. And then you have to repair the big hole in the wall you made for access, and prime and paint...)
They DO sell new breaker panels with copper busses, but unless you work with a coastal wholesale house that gets a lot of call for them you usually have to special order them. If you are anywhere near the ocean (or working on a boat power system), they are a necessity, the salt air tears up exposed aluminum with a vengeance.
(The Boss had a big go-round with a customer on the cost when I insisted on a copper buss panel - a rental house where the owner didn't want to spend a dime more than necessary, but I didn't want to go do it again in 5 years because "You did a crappy job!!" The house is built on wood pilings over the beach,10' above mean high tide line, the old panel was physically fine except for the corrosion.)
If this sub-panel breaker box was scabbed on to your existing main panel (using the "10 Foot Tap Rule") because it is out of spaces, sounds more like you need to change out the Main Panel. Changing this sub-panel might be putting a band-aid on a limb amputation.
What does the rest of the electrical system consist of, and how big is the house? (Define the REAL problem...)
Changing out the Main can be a huge job if you have to upgrade from a 30A 4-circuit plug fuse fusebox from the 1930's or 70A "Crowfoot" six-breaker panel from the 1950's to a modern 200A 40-breaker panel, and then rooting out the bad wire in the house (anything before the 1950's is probably Rubber insulation, and suspect) to something approaching current standards - but it's still a Whole Lot Cheaper than rebuilding the house after the fire. Trust me on this.
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On Apr 26, 1:51=A0am, Bruce L. Bergman
When did the change to aluminum buss bars occur? I was not aware they had done that. Will have to check the panels here.
Dan

Oh heck, that started in the late Fifties, when Copper got more expensive than AL. They are the norm now for small panels - If the bars are tin plated, they are most likely Aluminum.
Some large industrial panelboards were designed to use Aluminum main busses in larger amperages - a lot of Zinsco (Sylvania) switchboard distribution sections and panelboards still out there that push 400A through big L-shaped extruded aluminum busbars to Q style breakers.
They usually leave Copper busbars bare, and the patina is the real symbol of Quality.
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The real problem here is that the breaker was on an aluminum tab . Al oxidizes , which creates a poor connection , which produces heat , which fries the tab . And that's why I replaced my whole house breaker box a couple years ago . I didn't have enough good tabs left for the essential circuits , much less the shop/shed and other niceties . Got a nice big one now with copper bus bars and tabs . And a dedicate hunnerd amp breaker for the shed ... now I need the city to upgrade my service !