a measure of illuminance in lumens per square meter. One lux equals 0.093 foot-candles.

a control device that varies the shaft speed to the driven load on a motor. One example is the variable frequency drive (VFD), sometimes called a variable speed drive. A VFD consists of an electronic [..]

a measure of heating efficiency on an annual basis. AFUE is defined as the heat transferred to the conditioned space divided by the total fuel supplied (in Btu) for a given heating season. The higher [..]

the basic unit of electric current, one ampere represents the rate of one coulomb of charge per second. It is defined to be the total net charge flowing across a given cross-sectional area of wire per [..]

all fluorescent and most metal halide lamps need ballasts to operate. Because the arc generated in a lamp has almost no electrical resistance, ballasts are provided to regulate the lamp current. Magne [..]

the ballast factor is the ratio of the light output of a fluorescent lamp to the light output of the same lamp operated on a standard (reference) ballast. The ballast factor is multiplied by the rated [..]

optimizes the performance of HVAC equipment and alarm systems by automating the interaction of building mechanical subsystems, improving occupant comfort, lowering energy use and allowing off-site bui [..]

a type of space heating equipment consisting of a vessel or tank where heat produced from the combustion of fuels such as natural gas, fuel oil, or coal is used to generate steam or hot water. Unlike [..]

rate of water evaporation equal to the evaporation per hour of 34.5 pounds of water at a temperature of 100°C (212°F) into steam at 100°C. One boiler horsepower is about 33,475 Btu per hour (about 980 [..]

a British Thermal Unit is the amount of heat required to raise one pound of water by one degree Fahrenheit. Approximately equivalent to the thermal energy of a kitchen match.