NEC 502.4(B)(4) requires all boxes and fittings to be "dusttight". NEC 500.2 defines dustight as "enclosures constructed so that dust will not enter under specified test conditions". It has a fine print note:
FPN: See ANSI/ISA 12.12.01-2000, Nonincendive Electrical...
I would like to install a 480V, 3ph, 60A, 40hp rated IEC receptacle on the load side of a 100A CB, IEC 60A contactor, and 23-75A adjustable electronic overload for a 30hp motor. I have used receptacles many times to feed portable motor loads that have a portable motor starter on them, but this...
I am looking for design references for busbar design. Specifically the physical design of bolted joints of busbar and the physical design for bracing due to magnetic forces induced by fault currents. My application is for 250VDC around 1000A but any reference would be fine.
Also if anyone...
For NEC Table 310-17, what is the definition of "free air"? A major manufacturer of motor control equipment has sized conductors to motor starters inside enclosures (such as a Hoffman NEMA 4 enclosure) based upon Table 310-17, ampacities in free air. I have always used this table for...
I am sizing motor leads to a 300hp motor. Per NEC, I need ampacity of 361A x 1.25 or 451A. The installation is in a locale that gets very hot. Temperatures over 110 deg. F are not uncommon. Using derate of .82 for 75 deg. C conductors at 105 - 113 deg F. ambient and code requirement of...
