Are "Magnetic Definite Contactors" same as relays
 

I'm looking on Ebay for a 50 Amp DPDT Relay. I'm finding a bunch of 50 Amp Magnetic Definite Contactors that look a lot cheaper. Would they be interchangeable? Thanks

Link Please. That would help a lot.

Looks like they're made for A/C units...

http://www.answers.com/topic/contactor

definite purpose contactors are nothing more than heavy duty relays. They are made specifically for switching large loads on and off.

I use one inside my control panel as a manual "OFF" switch for my 5500W element.

It is controlled by a 120V signal. I have a small switch on the front of the panel that passes 120V to the contactor's coil to activate it.

edit:
You wouldn't want to do a lot of switching with the thing, I wouldn't think. I don't think they are meant for high-usage. I flip mine on at the start of the brew session and then the PID controls the on/off of the heater element via SSR. When I want to absolutely turn the element off, I flip the contactor off.

Cool. They seem a lot cheaper than Relays of similar amperage too. I am planning on using it as the main on/off relay for my entire system. It won't have any more switching than just turning on / off my system.

Thanks for the information!

That's the most common usage for the contactors. They aren't DPDT though, they're DPST (two poles, either on or off).

You can get DPDT contactors. One set of NC contacts and one set of NO contacts is how they are implemented... I think.

but, for an on/off switch, DPST is sufficient (and cheaper probably).

When I got mine, I was able to buy them on ebay for less than $7 shipped. Looks like they are going for more than that now.

Anyone have a link where one could find some of these?

I think this is the one I have:
http://www.pioneerbreaker.com/ProductDetails.asp?ProductCode=CN-PBC302-120V