240 – Overcurrent Protection

240.6(C) – Restricted Access Adjustable-Trip Circuit Breakers

Change at a Glance:

New provision added to recognize modern electronic trip units to provide the ability to set a password to keep unauthorized users from changing the settings on an adjustable-trip circuit breaker(s) that has restricted access to the adjusting means.

240.6 Standard Ampere Ratings.

(C) Restricted Access Adjustable-Trip Circuit Breakers. A circuit breaker(s) that has restricted access to the adjusting means shall be permitted to have an ampere rating(s) that is equal to the adjusted current setting (long-time pickup setting). Restricted access shall be defined as located behind achieved by one of the following methods:
(1) Located behind removable and sealable covers over the adjusting means
(2) Located behind bolted equipment enclosure doors
(3) Located behind locked doors accessible only to qualified personnel
(4) Password protected, with password accessible only to qualified personnel

240.87 – Arc Energy Reduction Method to Reduce Clearing Time

Change at a Glance:

Revision to 240.87(B)(5) clarifies that temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.

240.87 Arc Energy Reduction.

(A) Documentation. Documentation shall be available to those authorized to design, install, operate, or inspect the installation as to the location of the circuit breaker(s). Documentation shall also be provided to demonstrate that the method chosen to reduce clearing time is set to operate at a value below the available arcing current.

(B) Method to Reduce Clearing Time. One of the following means shall be provided and shall be set to operate at less than the available arcing current:
(1) Zone-selective interlocking
(2) Differential relaying
(3) Energy-reducing maintenance switching with local status indicator
(4) Energy-reducing active arc flash mitigation system
(5) An instantaneous trip setting that is less than the available arcing current. Temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.
(6) An instantaneous override that is less than the available arcing current
(7) An approved equivalent means

(See NEC text for Informational Notes)

240.88 – Reconditioned Equipment

Change at a Glance:

New section added dealing with reconditioned equipment. Molded- case circuit breakers shall not be permitted to be reconditioned.

240.88 Reconditioned Equipment.

Reconditioned equipment shall be listed as “reconditioned” and the original listing mark removed.

(A) Circuit Breakers. The use of reconditioned circuit breakers shall comply with (1) through (3):
(1) Molded-case circuit breakers shall not be permitted to be reconditioned.
(2) Low- and medium-voltage power circuit breakers shall be permitted to be reconditioned.
(3) High-voltage circuit breakers shall be permitted to be reconditioned.

(B) Components. The use of reconditioned trip units, protective relays, and current transformers shall comply with (1) and (2):
(1) Low-voltage power circuit breaker electronic trip units shall not be permitted to be reconditioned.
(2) Electromechanical protective relays and current transformers shall be permitted to be reconditioned.