How is the main breaker different?

In a typical house electric panel, electrically, a main breaker is the same as a regular breaker. That is if too much amperage is being used, it will trip and shut off the electricity.

Mechanically, a main breaker is pretty much designed to be a part of the panel itself. Not designed to be easily switched out with a different value breaker. Whereas with the other breakers in the panel, these along with their slots are designed to easily install different types and amperages of breakers as needed for particular circuits.

"Main breaker" is defining it's usage, not necessarily how it's built. The same thing with a breaker used as a service disconnect. The breaker is not necessarily different from a similar type breaker used in the same panel, however when used as a service disconnect, it requires a hold down method

Thank you.

Is there a technical reason why electrical panels with a main are so much more expensive (at least at HD) than main lugs?

Yeah, that's how the catalog is printed... :)

In reality doesn't seem there should be as much differential as there typically is other than that a 100 or 200A main is probably somewhat more expensive to manufacture than the typical 50/60A I've seen in the smaller subpanels.

(Maybe its my age and that we don't have any of the BORGs locally so don't know what they're carrying but I haven't seen a full-blown 200A panel w/o a traditional main--maybe they've started for the cheap/mass market and I've just not paid attention, though, granted).

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I would think that the main breaker would have a higher interrupt current rating than a branch circuit breaker, just in case things go really pear-shaped. (that is, if there's a *serious* issue, the main breaker will provide protection in cases of overvoltages/dead shorts that would just arc over an open branch circuit breaker.)

Now whether it works like that in practice, I don't know (IANAE)

nate

It's bolted in place. (you can use a regular breaker as a main, but it's supposed to be bolted in -- there's an inexpensive kit for doing that)

Bob

That is correct. The normal branch circuit breakers have a 10,000 a interrupting capability. Your utility may be providing a higher available fault current.

Another difference between the main and regular breakers is that on the main, the power is fed from the source to the terminal lugs, then to the busbar. A regular breaker gets the power in from the busbar and out through the terminal(s). Can breakers handle power feeds in either direction?

Yes, they can

Yes, I've seen it. One house I worked on the panel, they had a double 100 breaker feeding power in, and then the various breakers going out.

The house had problems with lights dimming, now and again. The HO and I switched the double 100 off, and pulled that breaker. Sanded the buss bar where the breaker fit on. Some anti oxidant on the buss, and into the end of the breaker. Put it all back together, and everything was fine.