Landscape Contractor / Design Build Maintain

APR 2017

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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April 2017 35 Wiring Garden Light LED recommends that all their LED lumi- naires be connected to a 15-volt AC tap on the transform- er. While all of their fixtures can operate at voltages as low as 12 volts AC, and some at even lower voltages, using the 15-volt AC tap results in the luminaire consuming less current. This is because the constant current driver, which is the device that converts the available input power into the power required to drive the LEDs, uses less current to do so when the voltage is higher. And less current also reduces the stresses seen by the wiring, the connections, and the driver. After wiring a system, Unique Lighting Systems advises to perform what they refer to as "the critical three." The first step is to check primary amperage –the amperage of the 120-volt power line – to make sure that the system is not exceeding the maximum allowed on the transformer. Next, the secondary amperage, that on the low-voltage side, should be checked to ensure that amount on each home run does not exceed the maximum allowed for the gauge of wire used (again using the 80 percent rule of the National Electrical Code). The third step is to check volt - age at the point of connection, such as a hub, to make sure proper voltage is being sent. LC DBM Top, Left For installation layouts, the straight run is the simplest but least efficient as each fixture down the line will receive less voltage due to voltage drop. This method is adequate for short runs where voltage difference is not more than 1.5 volts from first to last fixture according to Focus Industries. The split load method center feeds the cable run, minimizing voltage drop because it reduces only between the first and last fixture on either side of the run. With the loop method, the cable connects back to the transformer, providing voltage from both sides, which produces more uniform voltage to the fixtures. CREDIT: FOCUS INDUSTRIES Top, Right Evening Star advises using 12/2 landscape lighting cable (#6) when connecting fixtures using Power Tap Connectors, which are double-sided and will also accommodate 10/3 dual circuit cable; offering greater design flexibility. When splicing cable, it is recom- mended to use UL listed wire nuts suited for direct burial. CREDIT: EVENING STAR Bottom, Right When calculating the wire runs, Sollos Landscape Lighting suggests adding up fixture wattages per run. Then measure the approximate distance from the transformer to the first fixture on each run and use the chart to determine which voltage tap can be used for each run. CREDIT: SOLLOS LANDSCAPE LIGHTING Loop Run Split Load Run Straight Run

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