Circuit Breaker Sizing – Why I Recommend Choosing the Max Sizeįor many electricians, the Max Overcurrent Protection value doesn’t only reflect the unit’s maximum ampacity but serves as a “safety net,” too. Just know the Code makes it clear the values on the product nameplate, label, or official specs sheet override the NEC’s general OCPD guidelines. If you’re worried, then go ahead and match them. That technically means you can still remain Code-compliant if your unit’s wire and breaker sizes don’t match each other, as long as the conductor’s size isn’t below the MCA and the breaker’s size doesn’t exceed the MOP.Īre these setups practical? Most of the time, no, because they often lead to nuisance trips. That said, according to section 4(G) of the NEC, air conditioners have inherent overload protection, which means the wires won’t have to handle this electrical fault. You can choose to size the wire/conductor based on the MCA, as it should be.the MOP recommendation) if you have the means. I recommend you size the breaker as high as possible (i.e.To avoid complications, keep the air conditioning breaker size within the ranges displayed on the MCA and Max Fuse or Max Overcurrent Protection (MOP).Keep These Pointers in MindĪt best, you only have to remember these guidelines when determining air conditioning circuit breaker size: Both spare you from doing needless calculations, too. In the end, I just advised them to follow the figures reflected on the MCA and MOP of their respective units to avoid further issues like tripping or even overheating, which can even lead to fires. It turned out that the 20A breaker he used couldn’t handle the 22A rating of the heater, but the cooler only pulled 15A, so the unit appeared to work fine – until the heater kicked in, that is. One other client approached me, wondering why his 18,000 BTU unit tripped the breaker when he was running the heater but worked fine when cooling. It just so happens that both the heating and cooling amps didn’t go past that figure, so a 15A breaker would work fine with this AC. It dictates that the operating amps should not exceed 80% of the breaker’s rated ampacity.Ĩ0% of 15A is 12A. Long story short, I told her to use that air conditioner on 15 amp breaker.ĭid I make that recommendation because both the window AC unit amps are below 15A? Not at all, because I always consider the NEC’s 80% maximum load rule. It had cooling amps of 7A and heating amps of 11A. This is why 15-amp breakers are relatively popular for window ACs, especially if the unit runs on 115V or 120V.Ī customer once asked me how to size her 15,000 BTU AC. They also often don’t exceed 10,000 BTUs. Plenty of window AC units are rated for an average of around 8A. Circuit Breaker Sizing – Why I Recommend Choosing the Max Size.
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