Article 702 Optional Standby Systems

I. General



This article applies only to the installation and operation of optional standby systems.



These systems protect business or property where life safety is not dependent on the system. Power can be supplied either automatically or manually.


Application of Other Articles

Unless modified by this article, all provisions of the Code apply.


Equipment Approval

All equipment must be approved for this use.


Capacity and Rating

The system must be able to supply the entire load operating together. It must also be able to withstand the available fault current. The user can select the load which is connected to the system.


Transfer Equipment

Transfer equipment must be suitable for its use and designed and installed to prevent the inadvertent interconnection of the normal and alternate sources of power.

If it is located on the load side of branch-circuit protection, it can have supplementary overcurrent protection with an interrupting rating that can handle the generator available fault current.

There is an exception for temporary connection of a portable generator.



Audible and visual signals must be provided to indicate the derangement of the standby source and that the standby source is carrying the load.



The type and location of the system must be indicated on a sign at the service entrance. There is an exception for certain unit equipment. If the system is grounded to a remote grounding electrode a sign must be placed at the grounding location identifying all optional standby power and normal sources connected there.

II. Circuit Wiring


Wiring Optional Standby Systems

The wiring for this system can occupy the raceways, cables, boxes, etc., as the general wiring.

III. Grounding


Portable Generator Grounding

(A) Separately Derived System. Must be grounded to a grounding electrode in accordance with 250.30.

(B) Nonseparately Derived System. It must be bonded to the system grounding electrode.

IV. Sources of Power


Outdoor Generator Sets

The following article titles are listed for reference: Article 705Interconnected Electric Power Production Sources; Article 720Circuits and Equipment Operating at Less Than 50 Volts; Article 725Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits; Article 727Instrumentation Tray Cable, Type ITC; Article 760Fire Alarm Systems; Article 770Optical Fiber Cables and Raceways; Article 780Closed-Loop and Programmed Power Distribution.

Article 90 Introduction


Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions


Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction

Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120 © 2008-2020.
If you may any questions please contact us: