2.5.5.3
Terminal Blocks
a. Terminal blocks for control wiring shall be molded or fabricated
type with barriers, rated not less than 600 volts, type [_____]. The
terminals shall be removable binding, fillister or washer head screw
type, or stud type with contact and locking nuts. The terminals shall
be not less than No. 10 in size and shall have sufficient length and
space for connecting at least 2 indented terminal connectors for No.
19/22 AWG conductors to each terminal. The terminal arrangement shall
be subject to approval. Not less than 10 percent, but in no case less
than 2, spare terminals shall be provided on each block or group of
blocks.
b. Short-circuiting type terminal blocks shall be furnished for all
current transformer secondary leads and shall have provision for
shorting together all leads from each current transformer without first
opening any circuit. These terminal blocks shall be made by the same
manufacturer as the terminal blocks for control wiring listed above,
type [_____].
c. White or other light-colored plastic marking strips, fastened by
screws to each terminal block, shall be provided for control wire
designations. The manufacturer's wire number and the Government's wire
number shall both be shown for each connected terminal on the marking
strips with permanent marking fluid. The marking strips shall be
reversible to permit marking both sides, or two marking strips shall be
furnished with each block, to accommodate the two sets of wire numbers.
d. Load terminal blocks rated not less than 600 volts and of adequate
capacity shall be provided for the conductors of power circuits except
those supplied from air circuit breakers. The terminals shall be of
either the stud type with contact nuts and locking nuts or of the
removable screw type, having length and space for at least two indented
terminal connectors of the size required on the conductors to be
terminated. For conductors rated more than 50 amperes all screws shall
have hexagonal heads. For conductors rated 50 to 99 amperes the
minimum screw size shall be 8 mm 5/16 inch. Conducting parts between
connected terminals shall have adequate contact surface and cross
section to operate without overheating. Each connected terminal shall
have the circuit designation or wire number marked on or near the
terminal in permanent contrasting color.
e. Special attention shall be given to wiring the terminal arrangement
on the terminal blocks to permit the individual conductors of each
external Government-furnished cable to be terminated on adjacent
terminal points. The wire (terminal point) designations used on the
Contractor's wiring diagrams and printed on terminal block marking
strips may be according to the Contractor's standard practice; however,
additional wire and cable designations for identification of remote
(external) circuits may be required.
2.5.6
Grounding
The switchgear assembly shall include a full-length interior ground bus of
copper or aluminum bar to which the housing, framework, cable supports, bus
supports, and non-current carrying metallic parts of all equipment and
conduits shall be grounded insofar as practicable. No soldered connections
shall be used in the ground leads. If the operating mechanism of drawout
units is not permanently grounded, ground contacts shall be provided to
SECTION 16404A
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