The dashed line indicates that the two switches are mechanically connected. The flow switch shown in second Figure employs two separate contacts, one normally open and the other normally closed. A combination push-button station with a hand-off-automatic switch and pilot lamp is shown in above Figure. When the HOA switch is placed in the Auto position, a thermostat controls the action of the fan. In this mode, the fan will run continuously until the Stop button is pressed. This permits the motor to be controlled by a start-stop push-button station. When the hand-off-automatic switch is set in the Hand position, connection is made between terminals 1 and 2. Hand off Auto Switch Schematic.jpg 939×626 66.2 KB A warning lamp indicates that there is no flow of water when the circuit is energized. Flow switch FS1 detects the flow of water to insure that the fan motor cannot run if there is no flow of cooling water. Starter M1 controls the fan motor, and starter M2 controls a pump used to circulate water through the motor. The motor in this example is water cooled: it requires a flow of cooling water when running.
This circuit is the control for a large fan that pulls air through a building. When set in the Automatic position, connection is made between terminals 3 and 4. When set in the Hand position, connection is made between terminals 1 and 2. The switch chart indicates that when the switch is in the Off position, there is no connection between any of the contacts. One set is labeled 1-2 and the other is labeled 3-4. This switch is shown to contain two separate sets of contacts. Hand off Auto Switch Operation.jpg 556×604 52.1 KBĪnother symbol for a hand-off-automatic switch is shown in Below Figure.
0 kommentar(er)
