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