AT-2470 -- Conserving Energy in Dual-Duct Systems by Reducing the Throttling Ranges of Air-Temperature Controllers PDF

The throttling range of a controller that regulates the air temperature leaving a hot orchilled water coil is the change in air temperature needed to operate the water valve betweenzero and full capacity. The throttling range is a normal characteristic of controllers and isinversely proportional to the "gain" of the controller. In those types of air-conditioningsystems experiencing simultaneous heating and cooling, extra energy is required for both heatingand cooling because of the throttling range. During operating modes when the penalty ofthe throttling range is most severe (part-load operation), the energy required for both heatingand cooling could be reduced by approximately 10 percent, for example, by reducing the throttlingrange from 6°C to 2°C. The process of reducing the throttling range on most commercialcontrollers is a simple field adjustment.