SSR replacement for electric motor contactor

[Larry Cruzen]

I am looking for a double pole solid state relay to replace the exiSting motor contactor in an air conditioner. Needs 24VAC input. I can find lots of inexpensive single pole SSRs, but not double poles to switch both legs. Zero current switching would be nice. Seems like this would a common item.
Larry Cruzen

 

[itsmoked]

They do exist. A very bad idea for motor starting. They fail closed don'tcha know. How do you provide the legal requirement for motor overload protection using an SSR? Not sure how you even size them to handle the motor starting current..

Carlo Gavazzi
Though I wouldn't use Carlo Gavazzi crap if you paid me to.

[URL unfurl="true"]https://www.e-catalogue.celduc-relais.com/en/8-three-phase-ssr[/url]

Grainger

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

So you want to look for a "solid state contactor" or SSC, not an "SSR". SSRs are for little stuff, not motors. Most of the large motor control mfrs offer them.

SSCs will reject approx. 1.5W per running load amp per pole. You didn't post a current rating you are looking for, but if your load is 10A for example, the SSC will reject 30W of heat. It doesn't seem like much, but if the contactor is enclosed and not ventilated, it builds up. It also gets to the point where the heat sink for the SSC becomes somewhat large. In addition, SSCs are typically not able to handle operating temperatures greater than 40C (104F), so if this is going outdoors, that might be problematic too.


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