Electrical Codes Requirements for Low-Voltage Landscape Lighting

Definition

• Article 411 and the subsequent Underwriters Laboratory's paper, "The Standard for Low Voltage Landscape Lighting Systems, UL 1838," are the defining code most municipalities adopt as their own. Specialty UL codes also cover landscaping, interior and recreational vehicles. A low-voltage landscaping system is defined as an isolation transformer and cable to step-down the standard 120V current to low-voltage, connecting cable and the lights, or luminaries. It is not required for the transformer to have a clock or light sensor.

Transformers and Wires

• Transformers must be marked either as "indoor only," "outdoor only," or "indoor/outdoor." Care must be taken to use the correct transformer, as each is certified to a specified task and standard. The connecting cable for outdoor lights is generally SPT-3, Underground Low Energy Circuit wiring, although 16 through 12 AWG (American Wire Gauge) is often used for longer than normal runs. As electricity travels through wires, it loses some of its energy. Thicker wire enables more to be kept to the very end.

Cable Burial

• The number of lights allowed on any one transformer is flexible as long as the draw of the lights, or the amount of power they require, does not exceed the power of the transformer. One common violation of the code is the lack of burial of the connecting cable, according to Mark C. Ode of the "IAEI Magazine" for electrical inspectors. The cable is required to be buried about six inches, standard, and up to 18 inches under where vehicles travel.

Pools and Spas

• Swimming pools and spas are often installed incorrectly with low-voltage wiring, according to Ode. The NEC code requires at least 10 feet of separation between lights and the pool. If the lights are within five feet horizontally, then they have to be at least 12 feet above the water. Standard lighting is allowed between five and 10 feet only if the power supply is protected by a special GFCI circuit, which is not available for low voltage.