The terminals on the TB2 terminal block connect to an SPDT dry-contact relay in the A421 control. You can wire the A421 Electronic Temperature Control to use the same power source to power the control and power the controlled load. You can also wire the control to control the relay based on the on and off temperature values.
Relay de-energized: LC is open to LNO, as shown in the following figure, and the relay status LED is off.
Relay energized: LC is closed to LNO and the relay status LED is on.
In following figure, the relay is in the normally closed position. The green relay status LED is off. Connect a power source for the controlled equipment to LC. In standard applications, LNO supplies power from LC to the controlled equipment when the relay is energized.
