AC question

Being new to HI, I have a question for you seasoned professionals. While doing a maintenance job on a house, I noticed the customer’s AC was connected directly to the nearby service panel, which I suppose is not an issue. But I also noticed it was served by a 20 amp breaker, while being listed for 30. Other than a tendency for the breaker to trip, is this a hazard or deficiency? Please give me a detailed explanation, since I am not fully versed on the subject. In advance, thank you!

Which part of the A/C are you referring to, the air handler section (indoor) or the compressor section (outdoor)?

A picture of the AC label would be helpful.

Compressor. I got a direct call from a member who provided me with great information. Thanks.

Care to share that info for someone reading this thread who may have a similar question?

Okay,let me give it a try. I noticed an AC compressor had a 20 amp breaker. I checked the tag, which specified a 30 amp breaker. According to the information I received, although it is not necessarily a safety issue (since it would simply kick the breaker at start-up, if at all) it should still be reported as deficiency since the manufacturer specifies 30 amps. More input from you folks is welcome.

The nameplate on the unit should have the two key pieces of information used in sizing the circuit conductors and also in sizing of the OCPD ahead of those conductors. One thing that you will find is that the two (conductors and OCPD) do not have to match as they would in normal branch circuits. You may see a #12 conductor on a 35 amp breaker which may be code complaint.

So find on the nameplate the MCA or minimum circuit ampacity, this value is used as the minimum conductor size. Next find the MaxOCPD or maximum overcurrent protective device, this value is used to determine the maximum ampacity at which the conductors can be protected.

The data plate only specifies MAXIMUM breaker size. It’s OK to use less than the maximum. I see it frequently.

Just an additional note. If the data plate says maximum fuse size…guess what it has to be protected by a fuse at some point in the circuit. If it does not specify CB or Fuse…then either would comply. I add this because you stated you are new .

True, you could use any value OCPD between the MCA and the maximum.