Use of Romex for Temporary Wiring

Romex is a trade name for non-metallic sheathed cable or type NMC. This cable is covered by an outer plastic insulation that protects two or three current carrying wires. The individual wires are also enshrouded in a continuous insulation. Placed in between the current carrying wires is a bare copper wire that is utilized for a grounding conductor. All electrical wiring is under regulation by the National Electrical Code (NEC). More specifically the temporary use of type NMC or Romex is explicitly covered under Article 305. Local electrical regulations maybe more strict than those rules listed in the NEC Article 305.

Amount of Power

The temporary use of Romex must not exceed the overall amperage allowed by the NEC. In other words, a 12 gauge Romex cable assembly must not exceed a total current carrying capacity of 20 amperes as allowed by Table(s) 310 in the NEC book. Generally Romex is utilized for the temporary installation of overhead lights and receptacles during a construction phase or an outdoor event. Basic installation rules still apply even though the Romex is not a permanent installation. The most primary of these rules is that the cable must be protected from all mechanical damage. In other words, the cable cannot be laid across a floor in which heavy traffic, vehicle or foot, will damage the plastic sheath. The cable must also be placed high enough so equipment, and personnel will not come into contact with the cable. Supports of the cable will vary due to the installation parameters and any local governing rules.

Circuit Protection

All temporary Romex or type NMC installations must be protected to the cables rated capacity by a ground fault circuit interrupter (GFCI) breaker. This type of circuit breaker is designed for use in outdoor, and wet areas. Due to the hazardous nature of temporary wiring, all circuit protection must be of the GFCI type. As described above, a 12-gauge Romex cable is rated for carrying 20 amperes of power. The circuit breaker protecting this cable must not exceed 20 amperes of protection. In other words, you cannot connect a 12-gauge Romex cable to a 30-ampere or larger breaker.

Length of Use

Type NMC or Romex maybe utilized for the duration of construction or the outdoor event. At the end of the construction phase, when local inspectors deem the permanent electrical installation is complete, the temporary wiring must be taken down immediately. There maybe various exceptions to this rule depending on the local regulations. In cases for certain outdoor events, the wiring may have to be inspected, and a special permit issued in order to allow power through the installed wires. Again local regulations must be consulted as those rules maybe greater than the regulations stipulated in the NEC.

References

• "National Electrical Code"; National Fire Protection Association; 1987
• Romex Wire

Resources

• Occupational Safety and Health Administration