Normally Open Contact Means

Normally open vs normally closed electrical switch contacts.

Normally open contact means.

Normally open switch contacts are in an open state at rest. There is a common electrical connection between a contact of each pair that results in only three connection terminals. Relays and contactors have two types of contacts each suited for different applications. Electrical switch contacts are typically classified as either normally open or normally closed referring to the open or closed status of the contacts under normal conditions.

But what exactly defines normal for a switch. Normally open relays default in the open position meaning that when they re not in use there is no contact between the circuits. 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. Before we get into what normally open and normally closed are let s clarify what open and closed mean.

It is difficult and in some cases impossible to mix normally open and closed contacts on a single zone. Perhaps the most confusing aspect of discrete sensors is the definition of a sensor s normal status. Normally closed nc contacts allow current through when the relay or contactor is not energized. Meaning pronunciation translations and examples.

When buying contacts look for form c spdt single pole double. When power is introduced an electromagnet pulls the first circuit into contact with the second thereby closing the circuit and allowing power to flow through. Normally open no contacts allow current when the relay or contactor is energized. When replacing an existing contact you also need to know if the contact being replaced was normally open or closed especially if more than one contact is wired into a zone.

In other words when voltage is applied to the relay contactor terminals this contact closes. What is open and closed. As with so many topics that we try to simplify by associating with something we are familiar with associating electrical current flow with water flow causes a tremendous amount of misunderstandings. Form c contacts change over or transfer contacts are composed of a normally closed contact pair and a normally open contact pair that are operated by the same device.