Loads Known, Need to Size a Switch

[Keph]

Hi, I have a fan and a pump whose peak and running loads are known and I need to size a simple switch to turn them on and off. I was told that for motors a switch with a horsepower rating is required, but there seems to be a difference in switchs' ratings for current and horsepower. It's fairly easy to match a switch on the basis of current, but I need to know how to actually convert the required load to a horsepower rating for the switch. Could someone point me in the right direction?

 

[buzzp]

What your after is called a pilot duty rated switch. They can have a VA (more meaningful) rating or a W rating. These switches are required when switching an inductive or capacitive load. Generally if the switch was designed to switch such a load, the certifying agency (in US its UL or CSA) will issue a pilot duty rating. Or if no safety approvals, the designer will issue these numbers. You might here the terms make and break rating as well, it means the same thing as the VA rating, generally. From the motor data sheet you should find some starting VA requirments. If not, call the manufacturer.