Compact Fluorescent Lamps

Marijuana Horticulture

by Jorge Cervantes

Available since the early 1990s, compact fluorescent lamps (CFL) are finally available in larger wattages. The larger CFLs are having a major impact on small indoor grow shows. CFLs are similar to long tube fluorescents but boast increased power, smaller size, and an electronic ballast that ensures longevity and precise spectrum rendition. Although not as bright as HIDs, they are available in Col White and Warm White spectrums and generate little heat. Compact fluorescent lamps are perfect for growers with a limited budget and a small space. They run cooler than HIDs and require minimal ventilation.

When CFLs were first introduced, wattages were too small, and bulbs did not emit enough light to grow cannabis. New large-wattage CFLs are much brighter than smaller, low-wattage CFLs. Several years ago, European companies started selling 55-watt CFLs and Home Depot began to sell a 65-watt CF flood light for $30. Soon afterward 95, 125, and 200-watt CF lamps made in China became available in North America and Europe. The new lamps changed the way growers looked at CFLs. The new CFLs provide enough light to grow cannabis from seed to harvest.

Compact fluorescent bulbs used to grow cannabis are available in two basic styles and shapes. Modular CFLs have independent bulbs and ballasts that can be replaced separately. the bulb is shaped like a long “U” with a two- or four-pin fixture. The 20-inch long “1U” 55-watt, dual pin base bulbs are common in Europe. Normally, two 55-watt lamps are placed in a reflective hod. Shorter U-shaped bulbs are common in North America, the United States, and New Zealand.

The second type consists of miniaturized fluorescent tubes packaged with an attached electronic ballast. The short lamps consist of several U-shaped tubes (designated 4U, 5U, 6U, etc, for the number of U-shaped tubes) that measure from eight to twelve inches not including the two to four inch attached ballast and threaded base. Smaller wattages fit into household incandescent light bulb sockets. Larger 95, 125, 150, and 200-watt bulbs require a larger mogul socket. Common wattages used for growing cannabis include 55, 60, 65, 85, 95, 120, 125, 150, and 200.

Light from CFLs fades fast and must be placed close to the plants. The bulb produces very little heat and can be mounted about two inches away from foliage to achieve best results.

Short U-shaped bulbs are most efficient when vertically oriented. When mounted horizontally under a refl3ective hood, much light is reflected back and forth between the bulb’s outer envelope and the hood, which markedly lowers efficiency. heat also builds up from the ballast. Both conditions lessen efficiency.

Save electricity in the grow house and replace incandescent bulbs with compact fluorescents. Compact fluorescents use about 75 percent less energy than incandescent lamps, and emit 90 percent less heat for the same amount light. If you replace ten 100-watt incandescent bulbs, you will save 750 watts f electricity!

Construction and Operation

Compact fluorescent lamps create light by passing electricity through gaseous vapor under low pressure. Compact fluorescent bulbs are coated inside with tri-phosphor which further expands light emission. CFLs must warm up about five minutes so the chemicals become stable before they come to full brightness. Like all fluorescents, CFLs require an appropriate fixture containing a small electronic ballast to regulate electricity and household electrical current. Ballasts are either attached to the lamp or integrated into the reflective hood. Smaller self-ballasted lamps screw into a household incandescent bulb socket. larger bulbs screw into a mogul socket. Each 1-U bulb is hooked to sockets with bi-pin connectors.

Compact fluorescent lamps will normally last 10-20,000 hours (18-36 months at 18-hour daily use). The life of a CF ballast is from 50,000 to 60,000 hours (seven to nine years at 18 hours daily use). Lamps with an attached ballast burn out three to six times faster than the ballast. When the lamp’s life is over, the lamp and the attached ballast are both thrown away, which means you are throwing away a perfectly good ballast! My preference is to use the long CFLs that are not attached to a ballast.

Compact fluorescent lamps can also be used to supplement the reddish-yellow spectrum from HP sodium lamps. However, the outer case covering the attached ballast is susceptible to deterioration from UV light. When used in conjunction with other HID lamps that produce UV rays, the ballast case deteriorates more quickly. Attached ballasts are not designed for humid grow room application. Couple this weakness to humidity with a bit of UV light, and bulbs burn out more quickly. The end of a ballast life is signaled when it stops. When the ballast burns out, remove and replace it.

Although CFLs are not considered hazardous waste, they still contain a little mercury and should be disposed of properly to avoid contaminating the environment. Place CFL bulbs in a sealed plastic bag and dispose the same way you do batteries, oil based paint, motor oil, etc., at your local Household Hazardous Waste (HHW) Collection Site.