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What's The Difference Between An AC And DC Switch?

You may wonder if there is a difference between an AC and DC switch. However, there is actually a dramatic difference between the current-carrying capacity of AC and DC circuits. These differences can be seen in the AC and DC ratings. 

The Role of a Switch

A switch is a device that is used to turn power on and off for an electrical circuit. They come in a small variety of mechanisms. While there aren't a lot of switch options, there are thousands of switch varieties that all are meant to make or break a connection with a circuit. 

How a Switch Establishes a Connection

AC and DC affect the way in which the switch establishes a connection in a variety of ways. One of the main differences is in whether you'd like a variation in the magnitude and direction of the current, such as with an AC current, or if you would like the direction and magnitude to remain consistent, such as with a DC current. 

Breaking a Switch: AC Vs. DC

When an AC circuit is broken, it can be broken much more quickly than with the DC current. A DC current is broken more slowly. The arc can be drawn out over an extended time period. This can lead to a situation known as pitting switch contacts, which can lead to overheating and possibly a fire. For this reason, in many applications, the AC circuit is the safest option.

The Load

The load you are trying to switch plays a large role in whether you should use a DC or AC current switch. When the switch is used to energize a heater or a light, it will begin moving toward that state immediately. With inductive loads, such as with a motor, the load will pull a large amount of current initially until it settles. These types of loads cause excess voltages that can shorten the life of your switch if it is not prepared for the load. A DC voltage is always lower than an AC voltage. 

Having Your Switch Certified

Choosing the right switch is essential, but you sometimes will not know which switch is right for you unless you have the switch certified to work with your particular application. A great way to do this is to become certified by the Underwriters Laboratory. Those in Canada can turn to the Canadian Standards Association for certification.