Way, way back in the olden days...
There was a 42 circuit limit on LIGHTING PANELS. (Only)
In a footnote, it was mentioned that if there were no lighting (and appliance-- eg 1-phase recepticals and such) loads, the panel was not deemed a LIGHTING PANEL.
That little detail skipped by most of us commercial electricians because we almost never touched a panel that would not be deemed a LIGHTING panel.
If you dig out your ancient Square D catalogs -- and peruse their I Line offerings it will be quickly apparent that 54 circuit panels were an industrial option from... forever.
The ancient panels would often termed 'controlling' because the industrial firm would turn the big motor(s) on and off back at the panel.
This practice pre-dates modern notions of motor control.
In the beginning, even switches were expensive, and so reduced to the bare minimum.
This practice dates into the 19th Century. You can see such devices in museums, or old photos. It's hard to believe that knife switches were used to control high horsepower switches -- but they certainly did in the field of electric traction motors! (railroads)
BTW, the guys throwing those switches looked like Dr. Frankenstien -- of moviedom -- with his googles and massive insulating gloves, as he threw his 'monster' switch.
That practice is exactly where the movie crew got the whole idea.
The actual wording never stated that it was permitted to exceed 42 spaces -- the wording was that LIGHTING panels were RESTRICTED to 42 spaces. It then went on to describe our common variety breaker panels as being just such restricted panels.
That restriction has been lifted because of the AFCI. It's now hopeless to construct a McMansion with only 42 spaces -- while meeting the code -- and using but one panel.
So, NEMA threw the limit away, and had the NEC agree.
BTW, there was a period when fuse boxes were restricted to just six fuses. Again, that limit was eliminated when it proved inconvenient. But, you will find simply no end of antique fuse boxes limited to just six.
With them, the residence could technically eliminate a MAINS cut-off. That's just how cheesy things were. (Think retrofit shacks.)
France, BTW, is still big into fuses, not circuit breakers. It's a sweet deal for fuse sales -- and fuse makers. Naturally, only French fuses will do.
Last edited by Tesla; 12/22/12 11:28 PM.