IEEE NESCIR583-2017 en National Electrical Safety Code.pdf

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1、 1 Copyright 2017 IEEE. All rights reserved. Interpretation Section 32. Underground conduit systems Rule 323B Manholes, handholes, and vaultsDimensions (2017 Edition, page 254) (11 September 2017) IR583 Question: Do the working spaces described in Rule 323B apply to underground structures with cable

2、s other than manholes? General Discussion: Rule 323B only mentions manholes in describing the working space required for cables. However, Rule 323B is invoked by Rule 341B2 as the clearances to be used in both manholes and vaults. Rule 323B is not written in a manner to describe clearances and equip

3、ment likely to be encountered in some secondary network vaults, which may contain equipment other than cables or an unoccupied wall. Rule 323B in the 2017 NESC Handbook does address manholes with transformers, but describes operating cut-outs that are not found on subway-type network transformers. A

4、lso, in some vaults, the clearances above, below, or adjacent to cables may still provide adequate work space for cables or other duties despite a short clearance directly opposite the cable. Interpretation The answer to the question is that the working space described in Rule 323B applies to manhol

5、es and vaults, but not to handholes. By definition, manholes and vaults are structures that are designed to allow the entry of personnel. The definition of a handhole is a structure into which personnel may reach, but not enter. Rule 323B provides dimensions for adequate working space within a struc

6、ture designed for personnel to enter. Therefore, as stated in Rule 341B2a, Rule 323B applies to manholes and vaults. Because handholes are not designed for entry, Rule 323B does not apply to handholes. _ National Electrical Safety Code and NESC are both registered trademarks and service marks of the Institute of Electrical and Electronics Engineers, Inc. The NESC is available from the Institute of Electrical and Electronics Engineers, Inc. (http:/standards.ieee.org/).