With the rising popularity of residential and commercial landscape lighting, end-users and homeowners have begun looking for systems and components that combine easy installation and adequate safety considerations in one package. Standard 120V systems are unable to meet these requirements, so the industry’s landscape lighting manufacturers have responded by adopting 12V low-voltage systems as the standard for outdoor applications. Low-voltage systems use smaller light sources, are easy to modify to accommodate changes in landscape layout, and are safer to operate and maintain than their 120V counterparts. In standardizing the 12V low-voltage system, manufacturers have made available various sizes of step-down transformers to convert a standard 120V source to a 12V supply. The components of the system may be easier to work with, but voltage drop must be considered and understood to effectively service the customer’s landscape lighting needs. Depending on its size and length, the conductor serving the fixtures of a low-voltage lighting system acts as a resistor.

As current runs through the conductor, a voltage drop occurs: the voltage at the end of the conductor is lower than at the source. Smaller wires and higher currents will increase the voltage drop by raising resistance and increasing the fixture load respectively. Voltage drop on a lighting circuit in a 120V system isn’t considered a major issue. The branch circuit currents are relatively low—usually 20A or below—and the standard wire sizes are usually large enough to minimize resistance problems. When working with 12V systems, however, the line current for any given load increases by a factor of 10. For example, a 100W 120V incandescent lamp draws .83A, but an equivalent load of two 50W MR16 12V lamps draws 8.3A. If you use the same size and length wire in both systems, the voltage drop in the 12V system will be 10 times greater than in the 120V system. In this case, voltage drop becomes a significant consideration. When the actual voltage delivered to a given incandescent lamp is lower than the lamp’s rated voltage, the light output will be reduced.

This relationship isn’t linear. When the voltage decreases to about 85% of its rated value, the visible light output is only about 50%. It continues to drop quickly from this point forward. Once you’ve finalized the lighting layout, you can control voltage drop by selecting the most effective gauge wire. The smaller the gauge, the less the voltage drop. A minimum light output of 50% for the last fixture on a given run is normally an acceptable limit. Table 1 shows the maximum wattage allowed at various distances from a 12V transformer for various wire sizes. You can use the information in Table 2 to identify the required wire size, length of straight run, and wattage load on a preselected value of light output at the end of any given cable. Many transformers have multiple taps on the low-voltage side of the unit that provide 12V, 13V, and 14V output. Using a higher voltage tap to offset the expected voltage drop helps maintain the desired light output by delivering a closer-to-rated voltage at the remote lamps.

This technique is used primarily where the distance to the first fixture is a long way from the transformer. Take care to avoid providing an over-voltage situation to the first grouping of fixtures, as this would shorten the lamps’ life. You can also minimize voltage drop by altering your cable layout design. There are several options you can use other than a straight run: Multiple straight runs can be made in several directions. Tee connections reduce voltage drop by using heavier gage cable for the primary feed. Draped Lace VestA loop design reduces voltage drop and allows the lighting units to give off a more uniform light output. Wooden Beaded Car Seat CoverIt’s important to match the wire polarity at the transformer connection in a loop layout. T-Shirt Manufacturers In Korea

Locating several smaller transformers closer to the end of your cable runs can also help limit voltage drop. If at all possible, you should center the transformer in the run. If the light fixtures are located too far from the 120V source, consider running a 120V feed to a transformer located closer to the low-voltage lighting fixtures. If you’re only trying to serve a few limited fixtures, consider using direct burial, 12V transformers for each fixture, which can be fed with a 120V source. Another way to minimize voltage drop is to use lower voltage lamps in your design. For example, 18W lamps are the preferred choice for spread lights, but you can also use 12W lamps. If you do decide to use lower wattage lamps, however, recheck your photometric levels so you don’t wind up with an inferior lighting design. Low-voltage lighting installations require a great deal of care during installation due to the high currents in the system. Placing too many fixtures on the circuit or using the wrong wire size can lead to a system overload.

Therefore, it’s important to troubleshoot the system after installation. The most common problems encountered in low-voltage landscape lighting installations are poor wire connections, too many fixtures on one transformer (overloading), and cables that are too small for the load. By understanding voltage drop, you can address these problems and implement a successful low-voltage lighting design. Low-voltage lighting will allow the end-user to change the landscape layout and ensure safe outdoor lighting. Liepold is a project management consultant for Progress Lighting in Spartanburg, S.C.Landscape lighting describes a large and varied family of outdoor lighting fixtures. These versatile, weatherproof lights can be used to illuminate pathways, flower beds, trees, fences, driveways, stone walls, doorways, and more.Some landscape lighting systems operate on "line voltage," the 120-volt current from your house. For DIY installation, though, we highly recommend low-voltage systems that operate on just 12 volts.

They're less expensive, easier to install, safer, and use less energy.There are dozens of low-voltage lighting fixtures and accessories available in a variety of styles, sizes, colors, and finishes. Nearly every system, regardless of its complexity, is composed of four basic parts.Transformer: The power behind every low-voltage system is the transformer. It plugs into a GFCI-protected outdoor electrical outlet and steps down the house current from 120 volts to 12 volts. Most transformers are equipped with a 24-hour timer that allows users to decide when the lights go on and off automatically.Transformers are rated according to the maximum wattage output. Models range from about 44 watts to 900 watts. To determine which size transformer you need, simply add up the wattage of all the lights in the system. For example, if you plan to string together 10 18-watt light fixtures, then you'll need a transformer with a wattage output of at least 180.Low-Voltage Electrical Cable: The cable used for landscape lighting is specifically made for burial underground.

It runs from the transformer to each light fixture in the system. Low-voltage cable is commonly available in 12-, 14-, and 16-gauge. The lower the number, the thicker the wire and the greater its capacity.Which cable to use depends largely on the size of the transformer and the length of cable you need. For example, a 300-watt transformer can power 100 feet of 16-gauge cable, or 150 feet of 14-gauge cable, or 200 feet of 12-gauge cable. Check with the lighting manufacturer to determine the proper-size cable to use for your specific system.Pathway Lights: Designed for installation along walkways and driveways, this type of fixture represents the most stylish and elegant of landscape lights. Shiny copper or plated-metal fixtures stand out, while green-, black- or brown-painted fixtures can blend in with the surroundings.Accent Fixtures: The unsung heroes of any landscape lighting design are the accent lights. These specialty fixtures, which are often hidden from view, include floodlights, spotlights, up lights, and wall-wash fixtures.

They're used to shine a light on trees, shrubs, walls, flower beds, fences, ponds, and other landscape features.Putting in a typical low-voltage lighting system requires three major steps: laying the cable, installing the transformer, and connecting the lights.Laying the Cable: Start by laying the light fixtures on the ground where you intend to install them. Space the fixtures 8 to 10 feet apart. Next, unroll the spool of low-voltage electrical cable and lay the cable beside the fixtures. If you come to an obstacle, such as a boulder, tree, or fence, string the cable under or around it.Now use a square-blade shovel to cut a 2- to 3-inch-deep trench along the line where you want the light fixtures. The trench doesn't have to be perfectly straight, so if you hit a rock or root, just go around it. You don't even need to remove any dirt from the trench. Simply stomp the shovel into the ground and pull the handle back and forth to open a deep V-shaped trench.Set the cable into the trench and push it all the way down to the bottom using a short, narrow piece of 1/2-inch-thick plywood.

Don't use the shovel or other tool; you might accidentally slice into the cable.Installing the Transformer: Low-voltage cable consists of two insulated stranded-copper wires stuck together. Peel them apart so you have about 4 inches free for each wire. Then use wire strippers to remove about 5/8 inch of insulation from each side. Slide the wires through the retaining strap on the back of the transformer and then insert one wire under the A screw terminal, and the other wire under the B screw terminal. Tighten the screws to secure the wires.Next, drive a pressure-treated 2 x 6 stake into the ground next to an outdoor electrical outlet. Attach the transformer to the stake with galvanized or stainless-steel screws. Secure the cable to the stake with insulated cable staples.Connect the Lights Attach a plastic "while-in-use" cover to the outdoor electrical outlet. This type of cover protects the outlet from rain and snow but allows easy access.Plug the transformer's power cord into the outlet.