Written By Dave Fetterolf
When evaluating landscape lighting techniques in generic terms, there are three basic ways to light: uplighting, downlighting, and pathlighting. The majority of lighting falls into the first category: uplighting. When choosing fixtures to use in uplighting, there are two basic choices: bullet fixtures or inground fixtures. Bullet fixtures are easy to install and relatively safe because they are typically installed above ground using a ground mounting stake. There is much more to consider when using inground fixtures.
Although inground, or below grade, fixtures are one the most versatile fixtures in the industry today, very rarely are they installed properly. This creates problems due to the fact that incorrect installation of these fixtures can cause problems with the lighting system as well as creating the potential for fire.
The lamps used in most low voltage below grade fixtures are either MR-16 or PAR 36 lamps, which both create enormous amounts of heat. Because of the enclosed nature of inground fixtures, it is important to follow the manufacturer’s recommended installation instructions. My bet is that most contractors have never read the fixture installation instructions and therefore install these fixtures in a hole that is dug just big enough for the fixture to fit in. This does not create the “void” needed surrounding the fixture to dissipate the heat that is created by the lamp.
The correct way to install below grade fixtures is to dig a hole at least one and one half times the size of the fixture. Small gravel is then used to surround the entire well of the fixtures to allow the heat to escape. The fixture should also be installed with the lens above grade so that any water falling on the fixture has the ability to run off and away from the fixture.
In landscape applications where mulch or straw is used as a bed cover, you must make sure that ingound fixtures are not covered due to the possibility of the heat from the lamp causing a potential fire. Even though the circuit protection in the transformer is designed to protect the system from short circuits and heat buildup, a lamp that is completely covered in dry straw or mulch can create the potential for fire.
In conclusion, my suggestion would be to take a few minutes the next time you or your employees begin to install a landscape lighting system, and read the manufacturers installation instructions. Along with possibly learning a new installation technique, this may be the best insurance you could have against potential dangers.