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| Direct Digital Controllers The EMS consists of an interconnected network of Direct Digital Controllers (DDC). Each controller regulates a local system or device according to its own program or programs from central commands. Each geothermal unit has one controller, allowing sophisticated control over heating and cooling algorithms and schemes. A simple example is the scheduling program that automatically sets back heating and cooling set-points during unoccupied times, such as at nighttime, on weekends, or over holidays. At each geothermal unit, the EMS monitors conditions such as space, air-intake and air-discharge temperatures, fault conditions and occupant thermostat commands. Each controller analyzes these inputs then controls the unit through the proper heating and cooling sequences to ensure a comfortable environment at maximum efficiency. Each DDC controller is fully programmable over a LAN (local area network); thus, individual controls throughout the entire building can be programmed from one central laptop computer, which can be located anywhere in the building. Each controller can be programmed to communicate and share data dynamically with other controllers. Users may check the status and conditions anywhere on the EMS and, with proper password authorization, can alter system schedules, set points and even individual control programming. The EMS also monitors and controls the variable-speed, water loop pumping system. Each unit was fitted with an actuator water valve that allows water flow only when required. Since the loop water flow fluctuates based on the number of units operating, the EMS determines the speed at which the variable-speed pumps must operate, thus minimizing pumping costs. Because electricity costs are largely based upon maximum electric demand, the EMS monitors information at the main electric meter. When high-demand periods arise, the EMS is programmed to turn off low-priority loads. This feature minimizes utility loads during peak periods and saves substantially on utility costs. |
