Provided by www.MikeHolt.com
All questions and answers are based on the 2020 NEC.
Q. What are the rules related to electrical continuity between metal raceways and metal parts?
A. every second. 300.10 [Electrical Continuity]metal raceways, cable armor, and other metal enclosures must be metallically bonded to a continuous conductor to provide effective electrical continuity [Sec. 110.10 and Sec. 250.4(A)]as shown in Figure 1.
Exception 1: Short metal conduits used to support or protect cables need not be electrically continuous or connected to the equipment ground conductor (EGC). [Sec. 250.86 Exception No. 2 and Sec. 300.12 Exception No. 1].
Q. What are the basic rules regarding electrical circuits and equipment installed to reduce the spread of fire and combustion products?
A. Electrical circuits and equipment must be installed so that fire spread or combustion products are not significantly increased. Openings around electrical penetrations into or through fire-rated walls, partitions, floors, or ceilings must maintain a fire rating (Sec. 300.21) using approved methods. Figure 2.
Note: A directory of electrical construction materials published by an accredited testing laboratory contains the listings and installation limits required to maintain the fire resistance rating of assemblies. Building codes also limit penetration on both sides of a fire wall. Outlet boxes shall have a minimum horizontal spacing of 24 inches when installed on opposite sides of a fire rated assembly. instructions.
Boxes mounted in fire rated assemblies must be listed for the purpose. If using a steel box, it must be secured to the frame member. Cut-in type boxes are not allowed.
Building code requirements limit penetration in fire rated assembly sections from 100 square feet to 100 square inches. So if a 4 by 4 metal box is 16 square inches, only 6 boxes (100 ÷ 16 = 6.25) are allowed in that section of the firewall per IBC 714.4.2, International Building Code.
This requirement also applies to:
- Class 2 power limiting circuit [Sec. 725.3(B)]
- coaxial cable [Sec. 800.26]
- fire alarm [Sec. 760.3(A)]
- fiber optic cable [Sec. 770.26]
These materials are provided by Mike Holt Enterprises, Leesburg, FL. To view Code training materials from this company, visit www.mikeholt.com/code.
