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Issue link: http://read.dmtmag.com/i/557483
LANDSCAPE DESIGN AND CONSTRUCTION today (100 to 300 watts) we should still use a 12, 13, 14, and 15 multi-tap transformer. Besides the potential shortening of lamp life, we should also think about the future and the potential "what-ifs." For example, what if your system is on the edge of 10 volts and you want to add lights? Or, what if your voltage changes from daytime to night- time? This is a typical situation and happens all the time because we usually check voltage in the daytime when it is typically higher by 5 to 10 volts than at night. Daytime line voltage at 130 volts 'in' giving 13 volts out of the transformer and 10 volts at the lamps can change at night to 120 volts 'in' giving 12 volts out of the transformer and 9 volts at the lamps. The other big voltage drop killer is that we typically tap into an existing outlet, and the home- owner adds something to that circuit, thus causing voltage drop. How do you solve this issue? If you have a multi-tap transformer, all you have to do is change to a higher tap at the transformer, and the voltage will increase to the lamp. WIRING METHODS Now let's move on to wiring methods. One of the most com- mon methods of wiring has been the "daisy chain." The daisy chain brings power to the first lamp (fixture) on a wire run, often called the "home run." That first fixture receives the most volt- age or power. The remaining fixtures get less and less voltage in sequence. The number of fixtures and the wattage of lamps along with the wire distance will determine the voltage disparity. Some- times in lighting designs, you are very limited on your wiring space. The one and only time a daisy chain method can be useful is when you mount fixtures above ground and out of the earth. As soon as you put the system into the ground, you are asking for trouble with bad or poorly made wire connections. There is really only one advantage to the daisy chain method, and that is when placing fixtures in hard-to-reach areas such as rain gutters, second stories and under fascia. There are many more disadvantages, including too many points of connection, time consuming install, difficult to troubleshoot, short wire leads do not allow for much movement at the fixture, and daisy chain- ing does not get equal voltage to all lamps. One last point of concern with the daisy chain method is that generally every fixture needs splicing into place, creating the mul- tiple points of connection expressed above. This greatly increases the potential of having a failed connection due to water infiltra- tion, or a bad mechanical connection resulting in a heat buildup and melting of the wire. Due to the large amount of potential voltage drop, you might also experience failing lamps and a poor- looking lighting job due to unequal voltage. Another common method of wiring is known as the "loop" method. The loop method brings the same voltage and power to both ends of the wire run. When using this method, the home run wire goes to the first fixture, other fixtures are then daisy chained while maintaining wire polarity (very important). After install- ing the last lamp, the second wire is "looped-back" to the first lamp and tied in. A similar method is used in irrigation by double feeding the sprinkler zone to help equalize the water pressure throughout. It works the same way in electrical wiring by pro- www.landscapeirrigation.com Landscape and Irrigation September 2015 21