9.6.5.1 Provide localized control of ceiling fixtures by installing pullcord switches
Installing pullcord switches may be the most practical way to provide individual control of fixtures in many applications. Consider pullcord switches for both new construction and retrofit applications. They have a lowbrow appearance, but they offer a number of potent advantages:
•they are much less expensive than switches installed remotely from the fixture •they are easily accessible at the task location itself
•it is obvious how to use them
•they move along with the fixtures when fixtures are moved to accommodate new space layouts.
The last of these advantages is an important aspect of maintaining long-term efficiency that is not available with other types of switching.
Other methods are available for controlling individual fixtures locally. For example, some manufacturers offer switching that uses an infrared transmitter that works on the same principle as a television remote control. This method is more technically glamorous, but it is more expensive, and it requires a transmitter that can get lost. A piece of string is hard to beat for simplicity and reliability.
Where to Use Pullcord Switches
This method is appropriate in a variety of environments. In retrofit applications, it is an effective way of providing individual control of light fixtures that are connected in groups. Typical applications are individual desks in large office areas and individual work stations in factories. Figure 1 shows a typical environment where they might be used.
The pullcord switch does not have to control all the lamps in an individual fixture. You can connect pullcord switches to turn off some of the lamps in a fixture. Or, you can install more than one pullcord to control different lamps in a fixture. Going the other way, you can install a single pullcord switch to control several fixtures. (This may involve some rewiring between fixtures.) The amount of lighting that an individual switch can control is limited by its current rating, which typically is a few amperes. If necessary, you can use a relay with a pullcord switch to control any amount of wattage.
Be aware that a light fixture may provide lighting for more than one work area. Do not install pullcord switches on such fixtures if the adjacent work areas may operate on different schedules.
Perhaps the main reason that this simple, powerful technique is not popular is the concern that a jungle of pullcords dangling from fixtures would look messy. Pullcords do not have to be unattractive. By using decorative tassels or other ornaments, an appearance can be created that is attractive, or at least amusing.
How to Install Pullcord Switches
Success depends on details. Work out the following aspects of the installation.
How to Install the Switch on the Fixture
The Achilles heel of common pullcord switches is the flimsy bead chain and string. Replace the cotton string with strong nylon cord.
Also, figure out a way to install the switch so that the chain and cord run free without binding or chafing. Common pullcord switches are designed to be installed on the sides of shop lights, which allow the chain and cord to hang freely. These switches typically extend the chain slightly more than a half inch (about 15 millimeters) beyond the side of the fixture. This is fortunate for fixtures that are installed in suspended ceilings, because it may allow the chain to clear the Tbars that support the ceiling.
Even so, the chains may not last long if they have to pass through ceiling tile. A better method is to install a small mounting plate for the switch anywhere on the ceiling tile that is convenient. A variation of this technique is to install a common junction box on the ceiling tile. You need to do this if you use one switch to control several fixtures. Do all wiring in accordance with your local electrical code.
This method of switching overcomes one of the main problems of lighting layout, namely, difficulty in adapting lighting control to changes in space configuration. Work out the details of your switch installations to exploit this advantage. For example, mount the switches on ceiling tiles. This allows you to relocate the switch to almost any position by shifting the tile to a different point in the suspension grid and by rotating it to different positions
Length of Cord
Adjust the length of the pullcord so that it is easy to reach, but not so long that it strikes the heads of occupants.
Tagging and Placards
Even though the operation of pullcord switches is obvious, instructions are important to provide permission and motivation. A handy method is to attach a small, durable plastic tag to the end of each pullcord that says, “Turn me off when not in use”. In addition, install placards at the original wall switches, if you decide to keep them. See Measure 9.4.1 for details.
Maintain Emergency Lighting