Relay Wiring tips and tricks Simple circut. What to look/lookout for

Typically if you want a circuit completed when energized you use C (Common) and NO (normally open). This means that the contact will close when energized and thus complete your circuit. However in some cases a relay is used to stop current from flowing and when energized the contacts used are C and NC (Normally Closed) meaning that the circuit is closed when the relay is off and open when energized.

Other things to consider if "rigging a new circuit".

More precisely, what exactly are you going to accomplish:
Turn On a motor, or light
Turn Off a motor, or light
or complete a timing sequence,
Turn On A heater
Lock out a motor
Isolate a motor

A simple relay works but you had better make sure 2 things 1. your relay is not TOO HEAVY on the VA of the coil (this would cause a control transformer to burn out) is the correct voltage coil, AND 2. BE SURE YOU KNOW WHAT HP OR AMP DRAW your relay will be expected to hold while energized (or de-energized which ever the case may be). This latter is the contact rating. Too small and it will burn out. Too heavy, well I see not much trouble with too heavy a contact rating except it usually has heaver VA draw form the coil the bigger the contacts are.

DOes this help you?