| This article will be a breath of fresh | | | | 2-gauge wire, which has a constant of |
| air for some of you and a gut wrenching | | | | 11920, or a 12/2-gauge wire, which has a |
| process for others. Without getting too | | | | constant of 7500. |
| involved within the process, I will say | | | | With this information and the constants, |
| this particular piece of the puzzle is | | | | lets figure a "run for fun". This |
| designed for the person that thinks with | | | | example shows a run for 80 feet and on |
| the left side of your brain. Their many | | | | the run, there are 4 fixtures that have |
| studies and books written about the left | | | | a 20-watt lamp in each. We have a total |
| side and right side of our brains. Many | | | | of 80 watts on a run of 80 feet and 12/2 |
| people enjoy a "good" living dealing | | | | gauge wire is used for the run. 80-watts |
| with issues relating to the left and | | | | x 80 feet =6400, 6400/7500 (constant) = |
| right side of our brains. This could be | | | | .85 voltage drop. Now subtract .85 |
| the start of another book relating to | | | | (voltage drop) from 12 (amount of volts |
| that subject; however, I am not going | | | | from source) and we have a resulting |
| there. Too keep this to the simplest | | | | voltage reading of 11.15 volts. I like |
| form I can, I will say our brain is | | | | to keep lamps in a range of 10.5 volts |
| divided into two sides. We have the left | | | | to 11.7 volts for peak performance; |
| side and the right side. | | | | therefore, the reading of 11.15 volts |
| The left side of the brain functions by | | | | fits very will within the range. The |
| way of using logic, facts, knowledge, | | | | main thing to remember is to choose the |
| math and science and is detailed | | | | lamp you want and need to do the job you |
| oriented. If you fall into this | | | | want. Once you decide on the lamp, |
| category, you will enjoy this article. | | | | engineer the system to supply the proper |
| Meanwhile, the right side of the brain | | | | voltage to the lamp. |
| functions by using feelings, images, | | | | A rule of thumb on sizing wire for runs |
| symbols, sees the "big picture", is very | | | | is to always go bigger if there is some |
| imaginative and believes things are | | | | doubt. The 10/2 gauge wire expense is |
| possible by taking risks. If you fall | | | | just slightly higher than the 12/2 gauge |
| into this category, I hope your partner | | | | wire; however, the peace of mind is well |
| is a left-brain person. This article | | | | worth the difference. I have included a |
| will be dull and boring for you even | | | | flowchart to use as an estimate on which |
| though it is an extremely important | | | | gauge wire to use on which run. This |
| process for you to achieve your "big | | | | does not replace the voltage drop |
| picture" on your home to create the | | | | formula and measuring every lead to |
| "WOW" effect you want. | | | | every fixture using a multi meter to get |
| My wife and I are a good team because | | | | the proper reading. For runs over 100 |
| she is a professional photographer, thus | | | | feet I recommend using the 12/2 gauge |
| a right brain person. I am a left-brain | | | | cable just because it can handle more |
| person. We compliment each other and | | | | with less voltage drop. QUICK WIRE |
| guess who takes pictures of my | | | | SIZING GUIDE: Use the guide to select |
| landscape-lighting installations. A good | | | | wire sizes for each run - "Are there |
| starting subject for this article is | | | | more than 100 watts lamp load on the |
| "voltage drop". Voltage drop is created | | | | run"? If your answer is, yes then you |
| by internal resistance to the flow of | | | | Use #10-2 / If your answer is no then |
| electricity through electric wire or | | | | the next question is "Is the run longer |
| cable. It is the difference between the | | | | than 100 feet? If your answer is no you |
| voltages at the beginning of a cable run | | | | Use #12-2 and if its Yes then you Use |
| compared to the voltage at the end of a | | | | #10-2. |
| run. We need to compensate for the | | | | WIRE AMP RATINGS: Wire Size #12/2 100w |
| voltage drop in order to keep the same | | | | 8.3A is recommended and the maximum is |
| voltage to all fixtures. If we do not, | | | | 192w/16A. Wire Size #10/2 140w/12.0A is |
| the end fixtures will have lamps with | | | | recommended and the maximum is 288w/24A. |
| low voltage and the results will be a | | | | You will notice the low chart gives the |
| decrease in brightness. This is why we | | | | wire size with recommended and maximum |
| can see the yellow looking lights at the | | | | figures. It gives reference to watts and |
| end of the runs. | | | | amps. Remember the formula: (Amps x |
| The formula for calculating voltage drop | | | | volts = watts Or Watts/volts = amps) you |
| is: Total Watts x Length of Run / Cable | | | | will be fine on amps using these |
| Size Constant = VOLTAGE DROP. You are | | | | guidelines. I keep a maximum of 110 |
| now asking yourself," What is cable size | | | | watts per run on 12/2 cable and 150 |
| constant". That is a predetermined | | | | watts on 10/2 cable. I know the system |
| amount and I will not show the chart for | | | | is not working hard and I feel that it |
| the different size cables. Instead, I | | | | will produce an efficient operating |
| will share the constants that you will | | | | system. |
| use for your system. Use either a 10 | | | | |