SSR vs Mechanical relay

[justshapes]

I am building an 8 x 8 x 12 foot oven with 12 elements and 2 controllers. The oven will have a removable partition in the center for the occasions when the twelve foot depth is necessary.

Is there an advantage to using the solid state relays (SSR) vs. the mechanical relays?

I don't mind having a spare parts supply of high AMP SSR's on hand if there is an advantage. I have CNC machines in the shop and RF noise/line noise is a major factor.


Mike

[JTW37]

I have the mechanical type in my oven and putting one in the other. They make noise, like click, clack whine. But they are not loud and it tells me that it is working properly without having to look. The SSR's don't make noise (as far as I know) but I haven't used them. I read where you need a GOOD heat sink or BLEWIE!! and you buy another. That didn't tell you much did it.

[CarWiz]

Originally Posted by justshapes

I have CNC machines in the shop and RF noise/line noise is a major factor.

That's one major advantage to the SSR. SSRs switch on the zero boundary of an AC cycle so the on cycle ramps. There's no hard switching and you don't get back-EMF from a coil.

There's a lot of noise and back-EMF induced on power lines with relays. You can also see sudden voltage drops and spikes as they switch on and off. A good line filter or APCs on your electronic gear would help.

And as JT noted, SSRs require a hefty heat sink for longevity. Also, when SSRs are used to switch heater elements, you should down grade their rating by about 30%. (Use a 100A SSR for a 70A load, etc.)

[LoneGunman]

SSR's can fail in the closed position, that alone is enough reason for me not to use them. I have never seen a contactor fail closed, I'm sure it can happen but in the 13 years I have been an electrician I have yet to see one.

[tedsfab]

we use only magnetic contactors in our ovens . a few reasons . cheaper , no need for a heat sink, and like stated when they fail they fail open and cannot due damage to other things .

[peter61]

Where can I get a contactor for my oven?I've had it with the ssr's

[JTW37]

Go to the top of this forum and look in the Sticky or use this link.

Oven Building Material Links post #15