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Spotlight on Transformers

by Billy Bradford

Choose the right one for your project

A clean installation behind a brick wall. The use of conduit provides a professional looking job. Photo courtesy of Tim Ryan, Firefly Professional Lighting. A transformer of questionable quality with small taps. The 10 and 12-gauge wires would not fit securely in the small taps, resulting in a meltdown (inset) that was luckily contained inside the case. Photo by Integrity Outdoor Lighting. These photos demonstrate a clean installation of a transformer. The installation has been color coded (see inset) and there is no guesswork when it comes to making sure all of the connections are tight and clean. Photo courtesy of Mike Gambino, Gambino Landscape Lighting.

In today’s world of low-voltage landscape lighting there is a vast array of transformers to choose from. While they are all meant to perform the same basic function of converting line voltage (120 or 240v) to low voltage (12 or 24v), they are not all created equal. Your transformer can be looked at as the heart of your lighting system. Wires might be thought of as veins and arteries to get the blood flow where it needs to be, while the fixtures and lamps are the muscles that get the job done. If the heart is not in good shape and functioning properly, you can’t expect everything else to work as intended.

While less expensive transformers might be considered as a way to increase profit margin, they will rarely do that. The better transformers on the market will not only perform better, but also provide the installer with a range of features to get the job done right while often using less wire, which many compensate for the initial higher cost.

When selecting a transformer, look for some key features. Will the transformer accept the controls you have chosen for the project? Does the transformer provide your system with adequate protection on the low-voltage side? Does the unit hold its rated voltage under load? Is it easy to install and wire up? Is it properly listed for use in the intended system and mounting location? Is it sealed from the weather and constructed of a material that will last? Let’s take a deeper look into these questions and find some answers.

When using even the most basic of controls, such as a timer and photocell, you will find that some transformers will not provide adequate room for a wide range of control devices. You can be limited to a singular type of control or find that the timer plug even interferes with the secondary breakers. A transformer that allows you to use the controls you have selected will make your job as the installer much easier while enabling you to offer your clients a broad range of control solutions.

Low-voltage transformers intended for landscape lighting are limited to 25 amps on the secondary side. Your selected unit should provide you with one or more means of protection on the common circuits. Some units do this via an automotive blade-type fuse, while a more common method is via magnetic breakers. Magnetic breakers provide an easy-to-reset means of protection similar to the circuit breakers found in your home. Some transformers also utilize thermal or surge protection inside, making them even safer.

One of the hallmark signs of a poor-quality transformer is the inability to hold voltage once a load is placed on the transformer. When called out to service systems installed by other contractors we have found less than 9v coming out of the 12v-rated tap on some units. These systems are usually recognized by low-quality equipment and questionable workmanship, not to mention a “what were they thinking?” design. More often than not, we have found the homeowners were never really satisfied with the performance of these systems, and the original installer has not been back to service the system since the installation. Higher-quality transformers will hold the rated voltage output with little falloff when loaded.

Anyone who has installed a number of different brands of transformers will note some are easier to install than others. Some transformers provide little room in which to work with your low-voltage cables. This can cause a headache when it comes time to hook up your system, and leave you wondering if the wires are fully installed into the taps, and if you will be able to easily get your meter inside to check your amperages. Assuming you have chosen a transformer that has taps for the connections, make sure the taps are of adequate size and are easily accessible. They should accommodate multiple 10 and 12-gauge wires easily and clamp tightly down, making a secure connection.

When looking at the listings and ratings of a transformer, the contractor should understand what these listings mean before selecting a unit. The label on the transformer should state either an ETL or UL listing. This means the transformer has been tested and has been deemed safe for the intended use of the unit. One should also be familiar with specialty transformers and where and when to use them. When installing in or near water, the installer may need to select a transformer with a pool and spa rating to conform to NEC codes. When a transformer is to be installed inside a building, check to make sure it is rated for interior installations, and check codes governing the routing of wires through walls.

Transformer failures may be due to the units not being well sealed from the elements. Water and electricity do not mix. Corrosion begins to form, and it is just a matter of time before the system will fail. When choosing the heart of your system, look for a casing that is well designed and will shed water. A snug-fitting door (preferably one that is removable to make installation of the transformer easier) and utilizing the conduit knockouts properly will help keep things dry inside. As a general rule, look for cases that are constructed of high-quality stainless steel. This not only provides a lasting solution, but also keeps the system looking great for years to come. The one exception to this rule would be the use of transformers intended, and rated, for direct burial or use indoors.

Properly sizing a transformer is also a common topic of discussion. Clients often add on to their lighting systems, so take this into account when selecting a unit. Another common practice is installing larger systems in phases. This can not only help make the cost more palatable for your client, but can keep you in contact with them for years to come, which may generate long-term referrals. Transformers should be sized with no more than 80 percent of its rated capacity being used. If your system’s lamp load is 300 watts, select a transformer in the 500 or 600-watt class. This will not only allow for some expansion or a few lamp changes as plants grow, but it will also help keep your lighting system operating smoothly.

Location, location, location The old business and real estate saying holds true when choosing a mounting location for your transformer. Care should be taken to obscure the transformer from view. Another consideration is keeping your transformer out of direct spray from irrigation systems. Units designed to be used below grade may come into play in instances when it is impossible to find a proper mounting location. Obscuring a transformer from view can separate a good installation from a great installation. Using natural surroundings and a simple 4x6 treated post this transformer was well concealed from view. Photos by Billy Bradford.

The author owns and operates Integrity Outdoor Lighting in Southern Mississippi and custom builds landscape lighting systems.