Local Law 51
Currently The NYC Rule for lighting under a sidewalk shed is a minimum 200 watt,3400 Lumen,standard incandescent lamps enclosed in vandal proof fixtures and spaced 15′ apart and 8′ above the the floor level. There are some changes being made real soon which can put your sidewalk sheds out of code.
What is a Lumen?
A lumen is a unit of standard measurement used to describe how much light is contained in a certain area. The lumen is part of a group of standard measurements known as the photometry group, which measure different aspects of light. This group also includes such units as the candela, which measures luminance, and the lux, which measures illuminance.Strictly speaking, a lumen is defined as one candela multiplied by one steradian, which can be expressed as: 1(lm) = 1(cd) x 1(sr). A related unit of measurement — although not part of the standard units — is the foot-candle, which is often used in photography and film. To really understand what a lumen is, it is important to understand these units: the candela, the foot-candle, the steradian, and the lux.
What is Luminous Efficacy?
Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power . Depending on context, the power can be either the radiant flux of the source’s output, or it can be the total electric power consumed by the source. Which sense of the term is intended must usually be inferred from the context, and is sometimes unclear. The former sense is sometimes called luminous efficacy of radiation, and the latter luminous efficacy of a source.
The luminous efficacy of a source is a measure of the efficiency with which the source provides visible light from electricity. The luminous efficacy of radiation describes how well a given quantity of electromagnetic radiation from a source produces visible light: the ratio of luminous flux to radiant flux. Not all wavelengths of light are equally visible, or equally effective at stimulating human vision, due to the spectral sensitivity of the human eye; radiation in the infrared and ultraviolet parts of the spectrum is useless for illumination. The overall luminous efficacy of a source is the product of how well it converts energy to electromagnetic radiation, and how well the emitted radiation is detected by the human eye.
There are three ways this term can be used: (1) The luminous efficacy of a source of light is the quotient of the total luminous flux emitted divided by the total lamp power input. Light is visually evaluated radiant energy. Luminous flux is the time rate of flow of light. Luminous efficacy is expressed in lumens per watt. (2) The luminous efficacy of radiant power is the quotient of the total luminous flux emitted divided by the total radiant power emitted. This is always somewhat larger for a particular lamp than the previous measure, since not all the input power is transformed into radiant power. (3) The spectral luminous efficacy of radiant power is the quotient of the luminous flux at a given wavelength of light divided by the radiant power at that wavelength. A plot of this quotient versus wavelength displays the spectral response of the human visual system. It is, of course, zero for all wavelengths outside the range from 380 to 760 nanometers. It rises to a maximum near the center of this range. Both the value and the wavelength of this maximum depend on the degree of dark adaptation present. However, anaccepted value of 683 lumens per watt maximum at 555 nanometers represents a standard observer in a light-adapted condition.