The National Electric Code (NEC) is published by the National Fire Protection Association (NFPA). NFPA 70E, the Standard for Electrical Safety Requirements for Employee Workplaces, is written to be compatible with Occupational Safety and Health Administration (OSHA) safety standards. This interlinking of standards has made NEC minimum space requirements for conduit installations part of OSHA's safety regulations. Electrical work must be done in compliance with OSHA, NEC and NFPA standards.
OSHA and NEC
Minimum space requirements around conduit ensure access in an emergency such as during a fire as well as sufficient space for safe working conditions during repairs. "The Electrical Safety Program Book" states: "Instead of a set of code or standards, as in OSHA, NEC is a single code." NEC requirements are based on the type of work or the type of hazard. According to the "The Electrical Safety Program Book": "OSHA regulations 29 CFR 1910, Subpart S and 29 CFR 1926, Subpart K define requirements based on the type of work environment, such as general industry, construction or utility."
OSHA regulation 1910.333(A) is based on NFPA 70E-110.8(A). Subpart S of 29 CFR Part 1910 was written based upon the NEC. Electrical installations and conduits are classified as hazardous spaces, according to OSHA. OSHA 1926.404(c)(1) defines the minimum spacing between conductors as well as around them. OSHA 1926.407(a) classifies any location where fire can break out as hazardous. OSHA requires third-party certification of electrical installations to verify its safety and adherence to NEC standards.
Minimum Space around Equipment
The National Electrical Code (NEC) defines the minimum working space around electrical equipment. At least 36 inches of space must be available in front of electrical equipment running at 600 volts or lower. Higher voltage lines have greater minimum clearances due to the increased severity of injuries upon contact. When electrical equipment is enclosed, the minimum distance begins at the closed door of the enclosure. There is no minimum working space for the back side of electrical equipment when regular access is not required. When cranes or hoists must be installed near electrical equipment, a minimum clearance of 30 inches is required. When conduit runs above the ground or a walk way, it must be at least 10 feet above that level.
Minimum Space in Buried Conduit
Underground service conductors must be buried at the depth specified by the National Electric Code or local municipal requirements. Electrical conduits must be buried a minimum of 24 inches below the surface of the ground. The insulated bushing for the steel conduit linking to the power meter must extend a minimum of 18 inches below ground. OSHA Section 1926.651 defines the minimum spacing requirements for trenching such as when conduit is installed underground.
- "Environmental Health and Safety"; OSHA Final Rule Updates Electrical Standard; Josh Cable; February 2007
- NFPA 70E: Standard for Electrical Safety in the Workplace
- "Residential Construction Academy House Wiring"; Gregory Fletcher; 2003
- "OSHA: Stallcup's Construction Regulations Simplified"; Mike Bahr, James Stallcup; 2003
- "The Electrical Safety Program Book"; Kenneth Mastrullo, Ray Jones; 2006
- "Stallcup's Electrical Design Book, 2005 Edition"; James Stallcup; 2006
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