Can the fan power saving resulting from retrofitting with Dadanco products be calculated simply?
Yes. As the change is to an existing system, there is no change to fan type, ducts and other airside characteristics, for which the formula for fan total efficiency can be used. This is: Total Efficiency % = qV x ptF 10 PR where qV = volume flow of air, m3/s ptF = fan total pressure, Pa PR = power absorbed by the fan, kW The 10 is a constant in this formula. If the fan total pressures are the same, as is the fan efficiency, then the power absorbed by the fans is in the ratio of the two air flow rates. The question can be answered best by giving an example from a project. Example The following is an example of how to calculate the reduction in fan power when Dadanco units replace old units that operated on higher plenum pressures. Given: The induction units in an existing system required 380Pa (1.5″wg) primary air pressure at the nozzles. The replacement Dadanco units require 200Pa, a reduction of 180Pa. The original and design total pressure at the primary air fan was 1500Pa (6.0″wg).
