contactors

[daver828]

I am a newbie to the forum, so hope I'm in the right place.

I would like someone to explain to me what a contactor is, and it's purpose. I have worked on several jobs, mostly residential, where these have been employed in outdoor lighting situations. The last two instances, there was a single circuit feeding the contactor itself, then various loads from the contactor. While the installation is fairly easy, I do not know the purpose of the unit. Sorry if this is too basic.

 

[iwire]

There are many reasons and purposes for contactors.

In the situation you describe a contactor is often used as it can switch many separate circuits but be controlled by a single pole time clock and / or a basic photocell.

 

[hey_poolboy]

Contactors are also useful to control a higher or lower voltage.
I commonly use contactors with 12v. coils to control 220v loads.

 

[celtic]

Simply put...a contactor is a large switch controlled by a smaller switch.

Imagine the size of a "standard" light switch you would need to land a #3 wire...pretty big.
You land the #3's on the contactor.

What makes the contactor "work" (switch on/off)?
A coil

What makes the coil work?
Could be a photocell, a time clock, even an actual 15A switch.

So let's say you are at your local mega-mart. The mega-mart wants ALL the (480v) parking lot lights to come on at the SAME time.

You install this baby:

See the blue photo cell on top of the enclosure...
See the transformer below it to the left...
See the contactor below the transformer...
See the coil..middle of contactor, 1 red wire, 2 white wires.

The photocell will energize the coil on the contactor (by using the transformer) to close the contactor.

The photocell is probably 480V, but the contactor's coil is 120v, while the lot lights are also 480v...that's why we have that transformer in there.

The switches at top right, are probably HOA.

http://www.ripleylightingcontrols.com/products/lighting-controls/lighting-contactor-controller.htm#

 

[Pierre C Belarge]

Dave
Welcome to the forum.
Don't ever be uncomfortable asking any question here, that is the purpose of the site. If some are harsh, just ignore them, but most here are very talented and someone here seems to always be able to help.

There is a lot to learn, and fortunately todays technology is here for the choosing. I will link a site that I hope helps you.

www.allaboutcircuits.com

Check out Volume IV, Chpter 5 - then click on contactors

Good Luck

 

[mdshunk]

If you know what a relay is, you know what a contactor is. When a relay gets to be a certain size, it magically becomes a contactor. I'm sure some nerd at NEMA can tell you what the difference might be. Functionally, there is no difference.

 

[foqnc]

If you know what a relay is, you know what a contactor is. When a relay gets to be a certain size, it magically becomes a contactor. I'm sure some nerd at NEMA can tell you what the difference might be. Functionally, there is no difference.

And if you add overloads it grows up to be a Starter.