Landscape Architect Articles

Become A Lighting Expert03-27-06 | News

Become A Lighting Expert

By Thomas Meis, Nightscaping

A by-product of low-voltage lighting is heat, especially in the event of a short circuit or a loose connection. A loose connection will cause arcing, which generates a great deal of heat. Mulches are typically a type of wood product, which is combustible. You can imagine what happens next. Photo courtesy of John Meadors-MGM Inc.

It just so happens that12 volt outdoor lighting has become one of the fastest growing, most profitable services a landscape contractor can offer! Now more than ever it is important that professionals who offer lighting as a service become educated and proficient in all aspects of outdoor lighting.

Just as any musician who is preparing for a big concert, you must get your chops down. You need to become the expert.

A good lighting installation must begin with good planning. Some time must be spent before ground is broken to design the lighting system. Let?EUR??,,????'?????<

Why Light?

Your first step towards moving away from being just another fixture salesman is to find out what your client wants. What are their reasons for wanting a lighting system? Once you have listened, and determined their needs and wants, it is vital that you develop a comprehensive lighting design that encompasses the full spectrum of lighting elements to meet their desires.

The proper design procedure is to start by selecting the right lamps for the task. 12 volt lighting offers the contractor many choices in wattages and beam spreads. Photo courtesy of John Meadors-MGM Inc.

Proper Design Protocol:

Some contractors are content to hand their client a lighting brochure and tell them to select their fixtures. Once the client has selected their fixtures, then the contractor can install them. Everyone should be satisfied. After all, the client selected the fixtures, so the contractor isn?EUR??,,????'?????<

Voltage Drop

All 12 volt systems must be designed to function between 10.5 and 12.0 volts. Over 12.0 volts produces early lamp burnout, under 10.5 volts results in dim lights and a less than happy client. Voltage drop is a function of 3 factors: Wattage on cable run, distance from transformer and cable size. They are derived from Ohm?EUR??,,????'?????<

Often during the final nighttime adjustment it is necessary to move fixtures a bit to achieve the desired effect. Also, as plant materials grow they may need to be relocated. Extra wire allows flexibility to move fixtures if necessary. Photo courtesy of John Meadors-MGM Inc.

Selecting the Right Transformer for the Job

Choose a transformer which exceeds the wattage draw of the lamps on your lighting system. For example, if your system consists of 10 20 watt lamps, your total wattage draw is 200 watts. A 250 watt transformer will do fine for this situation, but the most important aspect to consider in transformer selection is UL 1838, the safety standard set forth for outdoor garden lighting. Paraphrasing, it states that the maximum allowable voltage for any secondary (12 volt) circuit is 15.0 volts, secondary side amperage shall not exceed 25 amps and must be fuse-protected on the secondary side, not the 120 volt side. Using a transformer that has the UL 1838 listing will allow you to sleep at night, knowing you have provided a safe product for your client, and it will get you through those tough electrical inspections.

Now, with design in hand, you are ready to get dirty. Grab your shovel and wire cutters (and a few more necessary tools) and let?EUR??,,????'?????<

Use different color flags to differentiate between different cable runs. For fixtures installed in trees or on structures, colored tape or ribbon will show your installers exactly where to place fixtures. Photo courtesy of Reynolds Landscaping

Now the fun part ?EUR??,,????'?????<

It is important that the trenches be opened with minimum disruption to the landscape. Before excavating, find out from your client if there are any important or treasured plants from relatives that need to be avoided?EUR??,,????'?????<

Trenches should be a minimum of 6-inches deep.This gets the cable away from cultivators, blade edgers and lawn aerators, and out of harm?EUR??,,????'?????<

Use a metal spike for grounding. Though highly unlikely, the potential exists for 120 volt power to come in contact with the 12 volt side of a transformer. Thus, the possibility of a metal fixture becoming energized with 120 volts can happen. Photo courtesy of John Meadors-MGM Inc.

Installing Cable

Gazebos, patio covers and arbors are all prime targets for outdoor lighting. Many beautiful effects are created by installing lighting elements to these and other structures. Check with your local electrical inspector or building department before affixing any 12 volt fixture or wire to any structure to find out what the local code will allow.

Install your cable runs as shown on the design.

One of the most important components of your lighting system is your splice. Make good splices and you will sleep well at night. It is important to use a high-quality, permanent, waterproof connector for all connections. As stated previously, a poor connection generates heat which can cause serious problems. Disconnections, corroded wire, melted connectors, melted cable, severe voltage drop, or worse?EUR??,,????'?????<

Always plug the transformer into a GFCI protected outlet and use a weatherproof outlet cover when installing in locations everywhere moisture might come in contact with the outlet. Photo courtesy of John Meadors-MGM Inc.

Location, Location, Location

Now place the fixtures in their locations, leaving as much of the plastic wrap on them as possible to protect them from fingerprints and dirt. When installing fixtures in the ground, it is important to use a metal spike for grounding. With a grounded metal spike, if someone were to come in contact with the fixture, the risk of a 120 volt electrical shock is eliminated. Protect yourself. Protect your client.

For fixtures mounted in trees, place them high-enough that they can create branch shadows on the ground. Use only stainless steel mounting screws when affixing a fixture to a tree. Fasteners containing copper will break down inside the tree creating copper sulfate which is toxic to trees and could kill them. It will cost you a bit to replace a dead tree! Keep in mind that tree bark grows laterally and that any fastener you use will ultimately be swallowed up if not maintained annually. For ease of maintenance, a stand-off bolt is an ideal fastener for attaching both fixtures and cable to trees. The stand-off will allow you to back off the fixture from the tree for several years before having to replace it with another fastener. Cables can be attached to the stand-off using zip ties. Cable hooks like those used for installing television cable are also an effective method of attaching wires to trees.

Time for the Transformer

Once all the fixtures are connected and installed, it is time to mount the transformer(s). Mount the transformer to a sturdy surface such as a masonry wall, a garage wall or a wooden post. You may need to install your own mounting pedestal. Regardless of what the transformer is mounted on, it must be installed 12-inches above the ground from the bottom of the transformer. Be careful when mounting the transformer to a side of the house. Transformers may hum during operation, which can resonate rather loudly inside the house and become a noise nuisance. A wall outside of a bedroom is usually not the best location.

This system is about ready to be powered up. Connect the cables to the transformer terminal blocks as determined in your lighting design. Tighten each cable securely to the terminal block, give it a good tug, then tighten it another quarter turn to ensure a snug connection. Label each cable as it comes into the transformer terminals to which run it is. Mark this down on your design for future reference. It is important not to exceed the amperage rated for any set of terminal blocks which is determined by the fuse on that terminal block. Typically this is worked out in the design phase and should not become an issue. However, better safe than sorry. One tool you must have as a lighting professional is an amp meter. With your cables hooked to the transformer and lights installed, turn the system on and check the amperage of each cable run. As stated previously, the maximum UL allowable amperage is 25 amps, meaning a 25 amp fuse is the largest fuse allowed. Thus, the sum total amperage of all the cable runs that connect to one single terminal block can not exceed 25 amps.

Bundle multiple cables together using electrical tape or zip ties. This makes for a clean installation in the trench and makes it easier to find wires in the future should you ever need to dig them up for repair or add-ons. At each fixture location, leave an extra 2 to 3 feet of cable spooled up so that the fixture can be moved in the future. Photo courtesy of Reynolds Landscaping

Double Check Those Voltage Drops

It is also important to double check that the voltage drop calculations you performed in the design phase will hold up under field conditions. With the lights on, test the terminal blocks for AC voltage. During the design phase, you may have determined that cable run A had an overall voltage drop of 1.2 volts. Thus, assuming a supplied voltage of 12.0 volts, there is no problem with supplying 10.8 volts to your last fixture. However, if your installed transformer output is only 11.5 volts, there would be a problem dropping 1.2 volts?EUR??,,????'?????<

Spend some time at night adjusting the fixtures to get the desired lighting effects. Walk through with your client and listen to them ooh and ahhh!!! Get paid, buy a big boat and go on a long vacation!!!

For more information go to www.nightscaping.com