Switch & Fuse Size

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Longer answer would be that you need to rephrase the question. What fuse? What switch? What feeder? Which comes first, in the circuit? Generally, the fuse (or breaker) is sized to protect the downstream feeder. But I don't know if that is the type of situation you are discussing.
 
charlie b said:
Longer answer would be that you need to rephrase the question. What fuse? What switch? What feeder? Which comes first, in the circuit? Generally, the fuse (or breaker) is sized to protect the downstream feeder. But I don't know if that is the type of situation you are discussing.
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If there is a fused switch that says 200AS/125AF. THe load siode of that feeder would be sized based on the AF rating?? Thanks.
 
horsegoer said:
The load side of that feeder would be sized based on the AF rating??
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Nope. Well, sorta yes, but actually no. You calculate the load first, then you pick the feeder size, and finally you pick the fuse size. So the AF rating of the fuse would be sized based on the ampacity of the feeder. You said it backwards. But if your basic question is whether to use the frame size or the fuse size, you have that part right.
 
The conductor is sized for the load, the fuse is sized to protect the conductors, the switch is sized to hold the fuse. I don't see the confusion here.
 
Jraef said:
The conductor is sized for the load, the fuse is sized to protect the conductors, the switch is sized to hold the fuse. I don't see the confusion here.
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The conductor size must be equal or greater load or fuse size :slaphead:
 
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