With regard to required spaces for routing conductors, it is the NESC that is silent. As we will show, however, in this case there probably will be plenty of room at the unoccupied end of the manhole. This particular NESC rule fits quite well with NEC provisions and we think it can and should be enforced. We think, however, that in instances such as this, where the NEC is silent as to required work spaces, the NESC should be consulted. Its provisions are generally less strict than the NEC. The NESC is designed to be used by highly qualified and supervised utility personnel. For example, in cases where NEC clearance rules apply, they should be applied because those rules are generally more strict. ![]() Remember, the idea is to apply the NESC in concert with the NEC, not to replace the NEC. EXCEPTION 1: Where one boundary of the working space is an unoccupied wall and the opposite boundary consists of cables only, the horizontal working space between these boundaries may be reduced to 30 in. The vertical dimensions shall be not less than 6 ft (1.80 m) except in manholes where the opening is less than 1 ft (300 mm), horizontally, of the adjacent interior side wall of the manhole. The horizontal dimension of the clear working space shall be not less than 3 ft (900 mm). Manholes shall meet the following requirements: A clear working space sufficient for performing the necessary work shall be maintained. (FPN): For additional information concerning such installations in an industrial or multibuilding complex, see the National Electrical Safety Code, ANSI C-2-1990. We think that the requirements in this section should be applied in concert with those in the NEC, as indicated in Sec. 323 of that code covers, in great detail, the required strength, dimensions, access dimensions and locations, cover supports, ladder requirements, drainage, ventilation, mechanical protection, and identification of manholes. There is, however, a workspace rule in the National Electrical Safety Code (NESC) that does apply. If, as in the case at issue, there is nothing that would trigger workspace requirements, then there is no minimum dimension limit in the NEC that directly applies to workspace access. If there were terminations that must be worked hot, however, then the installation would need to comply with the clearances given in Table 110-16(a) or Table 110-34(a) as applicable. 370-70), this requirement applies at all voltages. 370-28(b) (generalized to medium voltage by Sec. 110-12(b) requires accessibility to be maintained, but without giving any minimum dimensions. This isn't true of any other pull box, and the NEC does not include provisions that directly address this point, at least in terms of dimensional size. A manhole is unique in that, quite clearly, personnel must be able to enter and work within its confines. ![]() Nevertheless, the NEC does not include all the answers. ![]() The fact that the voltage is over 600V is irrelevant to whether or not it is within the scope of the NEC. We think that the installation is squarely within the scope of the NEC as covered in Sec. In this case, however, the service point is on the line side of this installation and the work appeared to be all premises wiring covered by the NEC. Note that with the voltage over 600V, traditionally this type of work has belonged to the electric utilities. In other words, the manhole is being used as a very large tee. Half of the conductors coming in from the 24-duct bank turn out toward the reader, and the other half go the other way. ![]() We were asked to comment on an installation similar to the one pictured in the drawing.
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