This week we want to discuss the difference between the standard AMP ratings for IEC and UL contactors. First we will simply define the two main types of ratings that are used for contactors. First is the most common AC-3 rating. This rating is used most often as the benchmark AMP rating for a contactor and should be used for inductive loads. The AC-3 rating is always lower than the AC-1 rating and if the application is not known this rating should always be used. The second type of rating is AC-1, which is always higher than the AC-3 rating and is used for resistive loads. This is less common as these are most often related to heating applications.
So why is this important? Well knowing which rating you need can save you money when ordering a contactor. You may look at the side of a contactor and see a rating of 32 AMPS and think you need a 32 AMP contactor replacement. While that may be the case, it would depend on whether that rating is AC-1 or AC-3. For example, the Schneider Electric LC1D09 contactor is rated for 20 AMPS AC-1 but only 9 AMPS AC-3. So if you read the side of that contactor and think you need a 20 AMP contactor, we would more than likely quote you a LC1D25 contactor (which is rated 25 AMPS AC-3) unless you specify that you need a 20 AMP AC-1 rating. This difference not only increase the size of the contactor, but also it costs two and a half times more that the LC1D09 contactor.