Load Shedding Ballasts- explained.

A building’s demand for electric power is the sum of the power required to run its electrical equipment in operation at any given time. Demand rises and falls as equipment is turned on and off. Peak demand is the highest level of demand over a given period. It’s the most expensive power the utility must produce, and these high costs are passed along to customers. Demand charges can represent 25% of a commercial building’s electric energy costs.

To encourage its customers to reduce demand during peak demand periods, utilities, independent system operators (ISOs), and other power providers are offering demand-response programs that provide financial incentives to building owners who agree to curtail load on request—either at scheduled times or during an emergency.

Building owners can significantly reduce their electric utility costs, therefore, if they can curtail load on a schedule, in response to price signals, or on demand by a utility—a strategy called load shedding. When it comes to lighting, this means switching or dimming. To address this need, the major manufacturers have begun introducing load-shedding ballast products.

Load-shedding ballasts:

* Provide a way to reduce input power upon an external demand
* Can be instant-start or program-start
* Can be bi-level switching, bi-level dimming or continuous dimming

Dimming is preferable to switching in occupied spaces in which users perform stationary or critical tasks—i.e., where changes in light output should be unnoticeable to a high degree.


How low can light levels go before occupants object? In developing a prototype for load-shedding ballast technology subsequently commercialized by lamp and ballast maker OSRAM SYLVANIA, the Lighting Research Center studied the question and concluded that they could dim the lamps by as much as 40% for brief periods without upsetting 70% of the building’s occupants or hindering their productivity. LRC studies also showed that nine out of 10 occupants accepted the reduction when they were told that it was being done to reduce peak demand.

Solutions are generally classified as low voltage (respond to a control signal from low-voltage wiring) or line voltage (respond to a control signal from line-voltage wiring). Low-voltage solutions enable integration of the ballast with other control strategies such as daylighting control and scheduling. Line-voltage solutions are well suited for retrofit because no low-voltage wiring needs be installed, just a signal transmitter.