Sewanee - The University of the South
IN-2: Innovation 2

Most-Open-Valve control of chilled water valves: we installed a central chilled water plant that serves the large central campus buildings. Air-conditioning is provided by 45 deg F chilled water that is pumped to the cooling coils in each building by a central pumping station in the central plant. Traditionally secondary chilled water distribution systems have been designed for constant flow. Eventually such distribution was done by variable flow through variable speed pumps. This variable flow has been controlled by measuring differential pressure in the piping system, typically near the central plant. We innovated a control system that greatly reduces pumping pressure and energy. We do this by using our Building Automation System to monitor the position of every chilled water control valve and supply only enough pressure to just barely satisfy the one having the hardest time getting water. This required the innovation of a new control strategy that in more recent times has come to be seen as the best, even though its use is still minimal, but increasing.