Abstract: A system for controlling delivery of either heated or cooled water to a plurality of heat exchangers includes a system controller which gathers information as to the current and future heating or cooling demands of a plurality of zone controllers associated with the plurality of heat exchangers. The system controller is operative to provide heated or cooled water to the heat exchangers even though current heating or cooling demands may not be sufficient to require the provision of heated or cooled water to the heat exchangers. The system controller does this by analyzing current demands for heating or cooling in combination with future demands for heating or cooling to determine if there is any combination of current and future heating or cooling demands that exceed a minimum level or number of demands necessary to authorize heating or cooling.