MCA v MOCP

[Chamuit]

I went to look at a job that was failed by an inspector. Two outdoor condensers.

First:
#10
20A MCA
30A Breaker
35A MOCP

Second:
#10
28A MCA
30A Breaker
45A MOCP

Inspector is saying that each unit MUST have a breaker matching the MOCP. I can't find anything in 440 that says I must use the Maximum OCP listed. Am I missing something here?

Neither unit has a minimum OCP.

 

[jumper]

I went to look at a job that was failed by an inspector. Two outdoor condensers.

First:
#10
20A MCA
30A Breaker
35A MOCP

Second:
#10
28A MCA
30A Breaker
45A MOCP

Inspector is saying that each unit MUST have a breaker matching the MOCP. I can't find anything in 440 that says I must use the Maximum OCP listed. Am I missing something here?

Neither unit has a minimum OCP.

Inspector is incorrect. A maximum is never mandated.

 

[Wrd4spd]

Agreed - As long as breaker rating falls between the MCA and MOCP, it complies with Code. You may have some problems with nuisance tripping on the second 30A circuit though.

 

[LarryFine]

IFirst:
#10
20A MCA
30A Breaker
35A MOCP

Could have used #12 wire; otherwise compliant.

Second:
#10
28A MCA
30A Breaker
45A MOCP

Could use a 40a breaker; otherwise compliant.

 

[ActionDave]

The inspector is incorrect, but I would install the larger breakers. There is no reason not to.

 

[infinity]

I went to look at a job that was failed by an inspector. Two outdoor condensers.

First:
#10
20A MCA
30A Breaker
35A MOCP

Second:
#10
28A MCA
30A Breaker
45A MOCP

Inspector is saying that each unit MUST have a breaker matching the MOCP. I can't find anything in 440 that says I must use the Maximum OCP listed. Am I missing something here?

Neither unit has a minimum OCP.

The minimum for the circuit OCPD is the MCA so for #1 you need a minimum of a 20 amp circuit, #2 minimum of a 30 amp circuit. If #1 uses a 75° C wiring method like MC cable and 75° C terminals/equipment you could use #14 conductors with a 20, 25, 30 or 35 amp OCPD.

 

[Chamuit]

Thanks, guys. Just wanted to make sure I didn't miss something that had changed. :blink:

I had a conversation with the inspector and explained it exactly as y'all have to no avail.

I am going to go back and install a larger breaker on the second unit anyway for the reasons mentioned several times above.

 

[infinity]

I would ask for a code section that's being violated.