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.
Normally open relay vs normally closed.
Gas valve control systems.
In these systems normally closed relays act as.
Relays and contactors have two types of contacts each suited for different applications.
A normally open is one that is an open circuit until you put voltage and a signal to it.
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 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.
Think of your relay as if it were two ends of as wire.
Normally closed relay applications.