See the Typical Control Icons box for descriptions of some of the CARE control icons. It minimizes the need for hard wiring to field-mounted switching devices. A switching table specifies the affected Excel controller outputs, determines switch status, and determines input conditions. When applicable switching conditions exist, the controller transmits the programmed signal to an output. An Exclusive OR table prevents software from transmitting more than one True condition to an output.
Users develop the switching logic on the schematic just as they do for the control strategy.
A typical switching logic sequence might be to start the return fan 30 seconds after the supply fan starts. This sequence is very simple to set up. The user locates the return fan control point on the schematic, assigns the status of the supply fan, and adds a 30-second delay. CARE's switching logic function can also handle some very complex applications that may include combinations of logical ANDs, logical ORs, or exclusive ORs. Also, there should be a differential on the discharge air temperature to keep the return fan from short cycling due to a change in temperature.