Less Is More: Saving energy with lighting dimmers

Photo © BigStockPhoto/Hywit Dimyadi
Photo © BigStockPhoto/Hywit Dimyadi

By Michael Liu
Building new homes and modernizing existing ones can be expensive. Project budgets are sometimes exceeded with unexpected surprises and elaborate aspirations; upgrades with crown mouldings, hardwood floors, cabinetry, and countertops all increase costs to the project. As with many renovations, the exceeded prices have no room for any additional expenses post-renovation. Homeowners and builders tend to forget to incorporate the final touches to make their project a work of art.

Rooms require lighting and controls to help achieve their décor. Flipping a light switch adds life to a space. Lighting controls also offer flexibility; by using dimmers instead of standard on/off switches, desirable ambient and task lighting can be easily set, creating a room with character.

Dimmers have evolved tremendously and have become very versatile in their applications. There are many options available to include different functions, colours, and designs that can suit any home. These lighting controls can also reduce costs.

Dimming versus switching
Dimmers provide flexibility to control a room’s lighting levels. When determining which area to install them, it is easiest to start with the most frequently used rooms. These usually include the kitchen and dining room as they are most often used to entertain guests and family.

When considering dimmer installation, its cost should not be discouraging. Typical on/off light switches are approximately $5 or less, compared to a rheostat dimmer that costs $10 or more. Its benefits surpass the price associated with purchasing a dimmer versus a light switch. The latter can only provide illumination at predetermined brightness levels as set by the lamping in the lighting fixture installed. On the other hand, a dimmer can offer multi-purpose functionality in several aspects, allowing for complete control of varying lighting levels.

Energy savings
Dimmer switches are typically easy to install in new buildings, and are simple retrofits for existing renovations. However, there are perceptions these products simply convert saved energy into heat lost through the dimmer’s components. Traditional rheostat dimmers use resistors so when a lamp is dimmed, they build up heat that will eventually be lost through dissipation as wasted energy. Innovative enhancements have developed an efficient method to provide a switch’s dimmability without energy loss in the form of heat.

A triode for alternating current (TRIAC) is a bi-directional switching device requiring only a brief pulse to turn it on. With an air-conditioning (AC) circuit, it automatically switches off when the AC voltage polarity reverses. This happens because the voltage (and therefore the current) passes through zero. The TRIAC cannot remain conducting with zero current, so it turns off. The process of switching on and off occurs 100 times each second (120 times for 60-Hz mains). The more a dimmer is turned down, the longer the TRIAC component shuts off. Every time it shuts off, there is no wasted energy, which decreases total consumption.

A typical dimmer can cost as little as $10. When it is used to decrease light by only 10 per cent, the homeowner can save just under $10 annually; by dimming the lights by 50 per cent, yearly savings in lowered energy costs can be up to $30.

There is also a reduced maintenance cost component to dimmers. Light bulbs do not generally burn out quickly from constantly turning off and on––it is the heat on the filament that normally wears out a bulb’s lifespan. When a dimmer switch is used, less heat and energy is used, decreasing bulb replacement frequency and lowering electricity cost.

A cinematic atmosphere can be created by adjusting levels of wall sconce and overhead recessed lights to provide optimal lighting for the room. Photo © BigStockPhoto/Bill Casey
A cinematic atmosphere can be created by adjusting levels of wall sconce and overhead recessed lights to provide optimal lighting for the room.
Photo © BigStockPhoto/Bill Casey

Types of dimmers
Typically, the most common dimmers are incandescent, low-voltage magnetic, and low-voltage electronic. Products in these three categories are capable of providing lighting controls for most residential lighting fixtures. There are also dimmers available to control the lighting output of virtually any light bulb available. Newer technologies, like light-emitting diodes (LEDs) and compact fluorescent lights (CFLs), are slowly becoming more readily produced to be used with dimmers.

Incandescent bulbs are the most standard and basic type of lamping available. Any type of dimmer would be able to vary the light output of incandescent bulbs. Line voltage halogen is another form of lamping used by standard dimmers.

Low-voltage magnetic
Low-voltage halogen fixtures involve transformers to convert the household 120-V into a lower 12-V state. These transformers typically come in two forms—electronic and magnetic. The two different types of step-down transformers operate differently. When selecting a dimmer, it is important to get one compatible with the transformer within the lighting fixture.

A magnetic transformer requires a low-voltage magnetic dimmer to properly control the lighting fixture. The magnetic fixture is inductive in nature; the step down from 120-V to 12-V is achieved by magnetic induction from a wounded copper coil over a steel core. A corresponding magnetic low-voltage (MLV) dimmer should be used to properly control the variation in lighting. This device operates in standard or forward phases—it effectively dims the transformer in the fixture by delaying the time the dimmer begins conducting.

An electronic transformer achieves its 12-V step-down by means of electronic circuitry. The small circuitry contains multiple capacitors that retain the stored energy (electronic transformers are capacitive by nature). Electronic low-voltage (ELV) dimmers are recommended when the fixture contains an electronic transformer. They operate in the reverse phase control, and function the exact opposite way of a MLV dimmer. Instead of delaying the time the dimmer begins conducting, ELV dimmers delay the time the dimmer stops conducting.

The difference between MLV and ELV transformers makes them difficult to dim when both types exist in a single circuit. There are no dimmers that can simultaneously operate both a MLV and ELV transformer. On the other hand, line voltage and low voltage can be mixed to be used on the same dimmer as long as the dimmer type is compatible with the low-voltage transformer.

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