heater control 2

[belcom]

pls i have heater tunnel with 8 element, 240v supply with on and off type of temperature controller. I want to know if i can use contactor to control the process, and which specification is best suitable. Thks

 

[itsmoked]

Probably a contactor will work. The question is really how often it will need to cycle which completely depends on the time constant of the tunnel. If it's too frequent the contactor life will be greatly abbreviated.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[melspuds]

As "itsmoked" stated a contactor will not last very long for temperature control. I suggest having a solid state temperature controller.
Hope this helps,
Dave

 

[belcom]

thks, @itsmoke and melspud for wonderful post, i really appreciate.

 

[itsmoked]

If the tunnel is large and thermally massive with product in it then once a minute or longer would probably allow a contactor. A contactor is usually good for about 150,000 operations. So with that in mind you can quickly estimate how long your contactor might last at whatever duty-cycle you will be subjecting it to. Of course the duty cycle is very dependent on the temperature control span you need to run the tunnel at. If you are fine with several degrees of hysteresis then you can see that the contactor will have far few cycles than if you're trying to achieve 1/4 degree accuracy.

Notice all the factors we can't know to help you decide?

Solid state control can allow ~50 to 500 million cycle lifetimes. However you usually need to include a safety contactor run by a second sensor and controller to detect a failed solid state relay (SSR). SSR also dissipate considerable power and require some thoughtful installation work or they fail in minutes.

Keith Cress
kcress -

http://www.flaminsystems.com