Normally Open Relay Vs Normally Closed

Think of your relay as if it were two ends of as wire.

Normally open relay vs normally closed.

Normally closed nc contacts allow current through when the relay or contactor is not energized. When it comes to electrical switches and contacts many people seem to be confused by the terms normally open no and normally closed nc the root of the problem seems to start with the fundamental concept of what it means to be open or closed this post attempts to clarify those concepts. In these systems normally closed relays act as. Normally open no contacts allow current when the relay or contactor is energized.

In other words when voltage is applied to the relay contactor terminals this contact closes. Here are just a few systems that require normally closed relays. Normally closed relays are used to keep ac unit blowers running even after the air compressor shuts off allowing the system to continue generating residual cool air without running the compressor. Normally closed relay applications.

A normally closed relay is one that is a complete circuit and therefore allows voltage to pass through it until it gets a signal and then it opens the circuit. Gas valve control systems.