Sizing a Frame/Trip in a main distribution panel

alixenos

Member
Location
Florida
Occupation
Electrical Design Engineer
Hello,

I have an Outside Air Rooftop Unit whose power specs are below.

Voltage: 208/60/3
FLA/MCA/MOCP: 24.3/28.8/45.0


I'm powering this unit from a main distribution panel.

1706285312082.png

The feeder number in the above picture is 8 that powers this unit.

I'm also providing a fused disconnect for this OARTU-1.

My question is, Will the breaker that protects feeder 8 be sized according to the ampacity of the conductor or according on the MOCP that is provided in the equipment (45).

my understanding is the breaker at feeder 8 should be speced to protect the ampacity of the conductor, and the fuse inside the equipment disconnect should be rated 45 amps to protect the equipment disconnect.


Thank you
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
my understanding is the breaker at feeder 8 should be speced to protect the ampacity of the conductor, and the fuse inside the equipment disconnect should be rated 45 amps to protect the equipment disconnect.
The conductor ampacity and the ocpd size do not have to match. Masterinbama gave you the correct answer.
 
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