I need to turn on and off a 1/3 HP 120 volt pump motor. I have a solid state relay which is rated at 40 amps 120 vac. Can I use this without a heat sink? It will turn the pump on for about 20 minutes at a time. The off time will always be more than an hour, usually several hours. Thanks for your help.
As a side note, I originally ordered a relay with a 5 volt coil with contacts rated at 12 amps at 120 vac. But when it came it was so small that I don't think it could possibly handle a 1/3 HP motor. (3/4 in x 1/2 inch x 3/8 inch)

 

no you shouldn't need a heat sink. But if it's in a panel, mounting it to the panel would be a good idea.

 

I was all set to say yes. My car’s radiator fans are controlled by SSRs and they’re mounted to the frame to cool it.

But your pump should be drawing only 2 amps or so, and I would not expect a heat problem on an SSR rated so far above that.

 

Yep I got 2A also and figured worst case 1.6V drop, for 3.2W dissipated. No big deal.