Voltage issues are a common problem when traditional (non LED) landscape lighting is installed by homeowners (non-professionals).
I get a lot of customers who are frustrated when their light bulbs burn out prematurely or when the lights at the end of the run are dim and not as bright as those closer to the transformer. A few rules of thumb I like to use are the following:
1- Always leave 15 feet of #12 cable between your transformer and your first light. This will prevent the first couple lights from getting 2 much voltage and having premature lamp burnout.
2-Don’t go over 100 watts per 100 feet on #12-2 wire. If you have runs less than 100′, you can put more wattage on you run and vice versa if you have a run longer than 100′, you need to put less than 100 watts. There is also a formula you could use below for measuring voltage drop.
Total Watts X Length of Run / Cable Size Contstant
Your Cable Size Constants are the following: #18=1,380, #16=2,200, #14=3,500, #12=7,500, #10=11,920, #8=18,960
If you stick these 2 rules, you will eliminate your voltage issues.
Another key element is PLAN before you start digging. Draw a simple diagram of how your fixtures will be placed with wire lengths from that transformer.
I hope you are reading this prior to installation, however, if not, it can be fixed!! In addtion, Landscape Lighting Company provides free design services if you purchase your lighting material with us.
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Have a Blessed day!
Dawn