Cable Sizes for Low Voltage Under Cabinets

Low Voltage

• When dealing with low voltages it is important to properly plan out the circuit prior to installation. As determined from Ohm's law, a low voltage is maintained with either a low current circuit or a circuit that possesses a very low resistance. While current may be lowered by removing devices from the circuit, resistance can only be lowered by changing the wire in the circuit. Changing the wire is only useful to a point, because the cost of very low resistance wire is often prohibitive or not practical.

Resistance

• The resistance is dictated by the device or devices that place electrical load on the circuit. In low voltage situations it is not uncommon for only one device to be placed on a circuit. Resistance may be lowered by using electrical wire with material of lower resistance, for example, copper instead of aluminum. Lowering the gauge of the wire -- using wire with a larger cross sectional area -- decreases resistance as well.

Current

• Current is the "positive flow" of energy through the circuit. At a specific voltage, only so much current may be allowed for any given resistance. This is the heart of Ohm's law. High current devices that use low voltage will require very low gauge wire to accommodate the device being used. In some cases it may be beneficial to use standard wire up to the appliance with a transformer that converts the current and voltage directly before the device itself.

Cable Sizes

• Resistance in a wire produces heat. This heat represents the lost kinetic energy from current as it is slowed inside the wire. It is imperative that the wire be able to accommodate the current requirements of the circuit. Failure to do this places the circuit in a position to ignite, causing an electrical fire. The NEC, National Electrical Code, provides data, including wire gauge charts, concerning electrical requirements for different circuits at different levels of current. When in doubt always go one cable size larger. The cost of doing so is well justified in terms of safety.

Common Wire Sizes Under a Cabinet

• The most common wire sizes that are installed beneath a cabinet range from approximately 8- to 12-gauge, as measured in the American wire gauge system. Twelve-gauge wire is the most common gauge found within a home and is used for almost all standard wall outlets and lighting. Cabinet lighting and electrical outlets installed within the cabinet are well served with 12-gauge wire. Larger gauges, such as 8 or 10-gauge wire, may be required for devices that place a larger load on the circuit -- such as a garbage disposal installed underneath a cabinet.