What Is 10/2 Romex Wire?
10/2 Romex is a nonmetallic-sheathed cable, type NM-B, built with two insulated 10 AWG copper conductors plus a bare copper ground. The “10” refers to the wire gauge and the “2” refers to the number of insulated conductors, a black hot and a white neutral or second hot. Romex is the common trade name for NM-B cable, and Southwire is the brand most electricians reach for. This cable is the standard choice for dedicated 30-amp circuits run inside dry, indoor locations.
10/2 Romex Amp Rating
10/2 NM-B is rated for 30 amps. The 10 AWG copper conductors carry a 30-amp ampacity in the 60 degrees Celsius column of NEC Table 310.16. Even though the individual conductors inside modern NM-B cable are insulated to 90 degrees Celsius, NEC 334.80 limits the usable ampacity of NM cable to the 60 degrees Celsius column. That is why 10/2 Romex is matched to a 30-amp breaker and not a larger one.
Common Uses for 10/2 Romex
Electric Water Heaters
A standard residential electric water heater runs on a dedicated 240-volt, 30-amp circuit. 10/2 Romex is the typical cable, using both insulated conductors as hot legs and the bare conductor as the equipment ground. No neutral is required for a straight 240-volt resistive water heater.
Air Conditioner Condensers
Many central air conditioner condensing units list a minimum circuit ampacity and a maximum overcurrent protection in the 30-amp range. 10/2 Romex serves these units where the equipment terminations and nameplate allow a 30-amp circuit. Always size the circuit to the unit nameplate.
Baseboard Heat and Small Subpanels
10/2 also feeds high-output electric baseboard heaters and short 30-amp subpanel feeders in dry interior locations. Subpanel feeders require careful planning for grounding and neutral separation, so confirm the design before running cable.
10/2 vs 10/3 Romex
10/2 has two insulated conductors and works for 240-volt loads that do not need a neutral, such as water heaters and air conditioners, and for 120-volt 30-amp circuits. 10/3 adds a red conductor and is required when the load needs two hots plus a neutral, such as an electric clothes dryer that uses both 240-volt and 120-volt power. Choose 10/2 for two-wire loads and 10/3 when a separate neutral is needed.
Code and Safety Note
All circuit and panel work should follow the National Electrical Code and any local amendments, and should be verified with your authority having jurisdiction. Match the breaker to the wire ampacity, and use a licensed electrician for new circuits, water heater hookups, and air conditioner connections. IB Lighting is a family-owned reseller led by a licensed master electrician, so the specifications here reflect current NEC practice.
IB Lighting stocks the full Southwire NM-B lineup inside our electrical wire and cable collection, with free freight plus free freight insurance included on every order. Call (800) 674-9019 for help selecting the right gauge for your circuit, or review our wire size chart.