The National Electrical Code® (NEC) is the preeminent electrical installation code in the United States. However, the NEC takes on real significance when adopted into law by states and local jurisdictions. The NEMA Field Representative Program advocates for the adoption of the most current edition of the NEC, with no state or local amendments, through participation in the code adoption process and collaboration with NEMA Member companies and other industry partners. As a founding Member of the Electrical Code Coalition, NEMA has partnered with the National Fire Protection Association (NFPA) to offer the following resources related to NEC adoption in the United States.

NATIONAL ELECTRICAL CODE (NEC)
NATIONAL FIRE PROTECTION ASSOCIATION (NFPA-7)
NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION (NEMA)
THE ELECTRICAL SAFETY FOUNDATION INTERNATIONAL (ESFI)

Adopted in all 50 states, NFPA 70, National Electrical Code (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards.

 

Abbreviation	Meaning	Description
S	SERVICE GRADE	Cord is flexible and designed for general use.
J	HARD SERVICE	Cord has a standard 300-volt insulation. If there is no J in the designation, the cord has thicker, 600-volt insulation, designed for heavier use.
W	OUTDOOR	Cord is rated for outdoor use includes sunlight resistant jacket and wet location rated conductors (formerly “W-A”)
P	PARALLEL CORD	Cord has a parallel wire construction, used in air conditioner cords and household extension cords (also known as zip cord)—Always light duty
E	THERMOPLASTIC ELASTOMER	Cord jacket is made from thermoplastic elastomer rubber (TPE) (UL/NEC designation ONLY)
T	THERMOPLASTIC	Cord jacket is made from vinyl thermoplastic
O	OIL RESISTANT	Cord is oil-resistant.
V	VACUUM CLEANER	Vacuum cleaner cord (also light duty cable)
H	HEATER CABLE	Heater cable
VW-1	FLAME RETARDANT	Flame retardant
FT2	FLAME RETARDANT	cord is flame retardant.
CL2S		wire is designed for in-wall construction
SRDT		wire is heavy duty and good for high amperage products.
HPN		Cord’s performance won’t be affected by the high temperatures associated with appliances.
SPT-1	STRANDED, PARALLEL, THERMOPLASTIC	0.030″ Insulation  2 or 3 conductors for grounding. (PVC) Indoor Use Only
SPT-2	STRANDED, PARALLEL, THERMOPLASTIC	0.045″ Insulation  2 or 3 conductors for grounding. (PVC) Indoor Use Only (SAME AS SPT-1 JUST heavier PVC)
SPT-3	STRANDED, PARALLEL, THERMOPLASTIC	0.060″ Insulation  2 or 3 conductors for grounding. (PVC) Indoor Use Only (SAME AS SPT-2 JUST heavier PVC)

Not enough cord for your lamp or radio to reach the nearest outlet? Just plowing through the junk drawer for an extension cord? This may not be a good idea. Extension cords can be very helpful in delivering power right where we need it. However, regardless of the gauge or rating of the cord, an extension cord is a temporary solution and is not meant to be used as a long-term extension of your household’s electrical system.

Using extension cords properly is critical to your safety. With continu­ous use over time, an extension cord can rapidly deteriorate, creating a potentially dangerous electric shock or fire hazard. The Electrical Safety Foundation International (ESFI) offers the following tips for staying safe from electric shock and electrical fires:

• Do not overload extension cords or allow them to run through water or snow on the ground.
• Do not substitute extension cords for permanent wiring.
• Do not run through walls, doorways, ceilings, or floors. If a cord is covered, heat cannot escape, which may result in a fire hazard.
• Do not use an extension cord for more than one appliance.
• Heavy reliance on extension cords is an indication that you have too few outlets to address your needs. Have additional outlets installed where you need them.
• Multiple plug outlets must be plugged directly into mounted electrical receptacles; they cannot be chained together.
• Make sure the extension cord or temporary power strip you use is rated for the products to be plugged in, and is marked for either indoor or outdoor use.
• The appliance or tool that you are using the cord with will have a wattage rating on it. Match this up with your extension cord, and do not use a cord that has a lower rating.
• Never use a cord that feels hot or is damaged in any way. Touching even a single exposed strand can give you an electric shock or burn.
• Never use three-prong plugs with outlets that only have two slots for the plug. Do not cut off the ground pin to force a fit. This defeats the purpose of a three-prong plug and could lead to an electrical shock. Never force a plug into an outlet if it doesn’t fit.
• Use extension cords with polarized and/or three-prong plugs.
• Buy only cords approved by an independent testing laboratory, such as Underwriters Laboratories (UL), Intertek (ETL), or Canadian Standards Association (CSA).

 

Extension Cord Designations

• S: Designed for general Use
• W: Rated for Outdoor Use
• J: Standard 300 Voltage Insulation
• T: made from Vinyl Thermoplastic
• P: Parallel Wire Construction (Air Conditioner Cords and Household Extension Cords)
• O: Oil-Resistant
• E: Made from TPE

Cord Length and Amperage Limits

• 25 – 50 Feet Extension Cords
  • 16 Gauge(1-13 Amps)
  • 14 Gauge (14-15 Amps)
  • 12-10 Gauge (16-20 Amps)
• 100 Feet Extension Cords
  • 16 Gauge (1-10 Amps)
  • 14 Gauge (11-13 Amps)
  • 12 Gauge (14-15 Amps)
  • 10 Gauge (16-20 Amps)
• 150 Feet Extension Cords
  • 14 Gauge (1-7 Amps)
  • 12 Gauge (8-10 Amps)
  • 10 Gauge (11-15 Amps)