Low Voltage Lighting Transformers Explained

Learn how low voltage lighting transformers can improve efficiency, reduce hum and consume less load power.

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What is the best kind of low voltage lighting transformer to buy?

These days, homeowners are clamoring for pendants that hang from the ceiling, moody undercabinet lighting, recessed lighting and outdoor path lights that illuminate the edge of the front walk.

Of course, none of those lighting fixtures will work if you don’t have them connected to a low voltage lighting transformer – a device that takes the high-voltage electricity running through a home’s walls and steps it down to 12 or 24 volts so that it can be safely run through a fixture.

But how do you know what’s the best kind of low voltage transformer to buy?

To find out, we asked Shannon Markey, LC, and the Western Regional Manager for Q-Tran, Inc., a Connecticut-based company that manufacturers transformers, to explain.

First, Markey said it’s important to know that there are two main types of low voltage transformers: electronic and magnetic.

Markey said although most lighting showroom owners are most familiar with electronic transformers, they’re not the optimal choice.

“The biggest positive benefit (of electronic transformers) is they tend to be very small and they tend to be less expensive,” Markey says.

But Markey says electronic indoor low voltage lighting transformers are sensitive to heat, so if you put them in a metal fixture or in a fixture with a canopy and the fixture gets hotter than its recommended temperature, the transformer’s lifespan will be cut short. In fact, for every five degrees Celsius it gets over its recommended temperature, the transformer’s lifespan is cut in half. Since they only have about a five- to six-year lifespan when operating properly, this means their realistic lifespan is even shorter.

Also, electronic low voltage transformers are known for being noisy, and homeowners often complain of a buzzing or humming sound coming from their transformers.

The Two Types of Low Voltage Lighting Transformers

When it comes to magnetic low voltage transformers, there are two types: stack laminated transformers, which are square, and toroidal transformers, which are shaped like a wire doughnut.

Like electronic low voltage transformers, the stack laminated transformers are inexpensive and have the added benefit of a longer lifespan, usually about 15 to 20 years. However, the stake laminated transformers only operate at about 80 to 85 percent efficiency, and they, too, are known for being noisy.

Toroidal transformers are more energy efficient. They operate at about 90 to 95 percent efficiency and can run for a very long time, anywhere from 20 to 25 years. They also are much more quiet, so you can place them close to the fixtures, rather than having to run wires a long way from the transformer to the fixture itself.
“You want to have your transformer as close to what you’re trying to light as possible,” Markey explains.

But the downside to toroidal transformers is their cost. Still, Markey says, “You can gain that back in energy savings over time.”

One of the most important things to remember with low voltage lamps, Markey says, is to make sure they are operating at their full light output. All low voltage halogen lamps are designed to operate at 12 or 24 volts. Although low-voltage lamps can be dimmed, if they are run at a lower light level all the time, the chemical reaction in the halogen bulb won’t work properly, and the lamps can blacken. If this happens, the lamp should be turned up high and run at its maximum voltage for at least 15 minutes.

To learn more about low voltage transformers, including how to use low-voltage transformers for outdoor applications, you can attend a seminar at Q-Tran's headquarters in Bridgeport, CT. The next seminar will be held on Friday, Dec. 5. For more information, visit www.q-tran.com.

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