When Sweep Switches Make Sense

Jan. 22, 2010

When you can’t start your lighting system from scratch, sweep switches provide an ecological, economical solution

In any significant remodel, lighting is always an issue – and a major part of the construction budget. With most states adopting model energy codes, such as the International Energy Conservation Code and ASHRAE 90.1, the use of automatically controlled lighting has skyrocketed.

For a new building, the sky’s the limit in terms of new, gee-whiz products; for remodels, the choices are limited.

Sweep switches are a niche product, but they’re particularly useful in renovation projects when it’s expensive and unnecessary to rip out an old lighting system.

These switches look and function like regular light switches, but add more functionality to an existing system, such as the ability to add local “manual on/automatic off” control without invasive modifications. They install like regular light switches and don’t require specialized control wiring. The system can be installed with the relay panels, digital time clocks, smart breaker, or computer-controlled contactor panels already in the structure. The result: increased control that leads to energy and cost savings.

Where and How They Work
Sweep switches work well in office buildings, tenant buildings, owner-occupied buildings, and warehouses. They save energy in any area where it’s beneficial to shut lights off automatically when no one is present (closets, sections of offices, storage spaces, etc.). They’re also ideal when an existing space is being modified to accommodate various tenants with different hours and lighting needs.

You should consider sweep switches in your building if:

  • It has an existing automatic lighting control system and is undergoing an improvement project.
  • More energy efficiency is needed for cost savings or to meet energy codes (or both).
  • Manual override control is needed, but replacing the existing automatic lighting control system is too expensive.
  • It’s being subdivided for new use or for tenants with different lighting needs.
  • The operations staff is familiar with the current lighting system, and putting in a new system would involve a steep learning curve.
  • The end-user or operations staff has strong objections to using infrared or ultrasonic occupancy sensing switches (these switches are frequently destroyed because people push the infrared sensors, thinking they’re buttons).
  • Automatic lighting shutoff would not endanger occupants.

Because sweep switches don’t sense movement, be aware that they can cause inconvenience and danger if the lights go out when the space is occupied. Also, sweep switches aren’t inexpensive, but they certainly cost more than a standard switch. For many buildings, however, adding a handful of sweep switches is cheaper than ripping out an old (but otherwise good) lighting relay system.

Installation and Use
Unlike standard wall switches, sweep switches are held in place electrically, not mechanically. They work with the existing relay panel or smart breaker with a time clock. At preset times, the power is momentarily interrupted. The lights go off, and the switch resets to “off,” making it easy and intuitive for staff or occupants to turn the switch on manually if needed. Turning on an individual switch won’t affect the entire system or any other switches – it simply means that those lights will stay on until someone manually turns it off, or until the next power interruption sweep, which is after normal business hours.

If you’re specifying sweep switches, you’ll need to plan for how the system works. Unlike traditional lighting relay systems, sweep switches don’t provide a flash warning (where the lights go on and off several times) to give occupants a signal that lights are about to turn off. To plan for this, timing and placement for automatic shutoffs shouldn’t leave people in darkness with difficulty finding the switches. The easy solutions for this:

  • Leave certain lights on to provide adequate illumination.
  • Use sweep switches in areas that are rarely occupied after hours, such as closets and storerooms.

An advantage of the individualized control over each switch is that, in a traditional relay configuration, when the lights go out, occupants would need to go to the master control station, which might be on the other side of the building, to override the system. With sweep switches, they simply go to the switch and turn the light on.

John Yoon is an electrical engineer with McGuire Engineers in Chicago.

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