| What do “old gray box” (OGB)
electrical enclosures have in common with Chicago’s historic Monadnock
Building? Load bearing walls.
This 17-story brick building at 53 West Jackson Boulevard was state of
the art when it was designed in 1889. But at that time designs based on
a framework of structural girders protected from the environment by
architectural panels were not yet in common use, so the Monadnock
Building relied on load bearing walls that had to be six feet thick at
its base to support the weight of the building, tapering to 18 inches
thick at the top.
Although their wall thicknesses don’t
taper, OGB electrical enclosures commonly used in U.S. electrical
control panels have one thing in common with the Monadnock Building:
Their structural integrity relies on their wall thickness instead of on
a sturdy framework protected from the surrounding environment by panels
affixed to that framework.
In the case of the Monadnock Building,
too-thick walls meant reductions in rentable office space. In the case
of OGB electrical enclosures, too-thick walls mean:
- Smaller door openings (and hence
smaller sub panels) because larger openings in OGB's front faces
would undermine the OGB's structural integrity.
- Walls that can't be removed for
easier access to during manufacture and installation;
- Thicker-than-needed walls that are
tougher to punch or cut, and;
- Excessively heavy enclosures that
are harder to move in the shop and more expensive to ship.
Rittal enclosures have more in common
with a modern skyscraper such as Chicago’s Sears Tower (now Willis
Tower) than with the Monadnock building. Like any modern skyscraper
built with a protective skin over a structure of girders, Rittal
enclosures rely for structural strength on a strong, solid frame and for
protection from the surrounding environment on panels affixed to that
frame.
Photo courtesy of Wikipedia: http://en.wikipedia.org/wiki/Monadnock_Building |
