Wiring to Normally Closed Connection

With a Single Pole Double Throw (SPDT) relay the relay will have a Common, Normally Closed and Normally Open connection.  When the relay is not energized or in the off state the arm from the common is at the Normally Closed state.  When Energized the arm swings to the Normally Open side.  If you wire a light to the Normally Closed side the light will actually go off when the relay is energized.  I think of this as wiring the relay backwards so that the light goes off when the relay is energized.  On rare occasions we get an application where wiring to the Normally Closed side is required. 

We offer SPDT relays in our 5, 10 and 20 amp versions throughout or site.