240v Temp controller & 120v contactor?

[Deecoat]

Hello everyone!
I'm in the market for a temp controller,and this is surely a stupid question.
I know I need a 240v temp. controller but do I need a 240v contactor also or just 120v one. Of course I only need 240v to the elements but was not absolutely sure about the contactor voltage. I need 2 of them so I want to make sure I get the right thing to begin with.

Thanks Everyone!
Darrin

[Popeye]

Dee,
A contactor or relay has two parts.. one is a set of contacts for switching a device on or off, if you have a 240 volt device and you want to switch that device on/off make sure the contacts are rated for at least that voltage and required amperage.
The second part is the control coil... when energized the coil closes the contacts (from above). The control coil will be rated for a certain voltage as well... 24, 110, 220 are the most common..

Your control voltage can be different than the contact voltage. I usually use 24 volt control now matter what voltage I'm switching... yours will depending on what your using for control voltage.

hope that helps

[CarWiz]

Contactors can have different voltages for the load and for the coil (solenoid). If you going to use 240v heaters, you want a 240v load contactor. You will also want the contactor to safely handle the amperage created by the heaters. The contacts are rated in amps. If you have two 3kw heaters on 240v, that's about 12.5A per coil individually but run in parallel, it's about 26A. (slightly more than double) Your contactor should be rated about 30A or more.

The solenoid coil on the contactor can be anything from 6vac to 440vac. If you want to run the contactor on 120v, get one that has 120v coils but make sure the contacts are 240v/30A+.

As a side note. I strongly suggest you use Solid State Relays (SSR) instead of contactors. Depending on the controller you use, the contactors will wear out in a hurry. SSRs will switch on 3-32vdc and will handle 240vac/30A+. SSRs can be switched directly from the SSR output on a controller. SSRs can also reduce light flicker in the shop since they switch on the zero boundary of an AC cycle. They don't shock the circuit like a contactor.

[CarWiz]

Ops, Popeye beat me to it. I guess I shouldn't walk away from the screen in the middle of a post.

[Popeye]

Wiz,
At least we're on the same page

[autobonifica]

Originally Posted by CarWiz

As a side note. I strongly suggest you use Solid State Relays (SSR) instead of contactors. Depending on the controller you use, the contactors will wear out in a hurry. SSRs will switch on 3-32vdc and will handle 240vac/30A+. SSRs can be switched directly from the SSR output on a controller. SSRs can also reduce light flicker in the shop since they switch on the zero boundary of an AC cycle. They don't shock the circuit like a contactor.

or you can be like me and over kill it. i'm using an industrial 100 amp mercury contactor