Nec 520.53(H)(3)

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erickench

erickench

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Brooklyn, NY
In the above section I find something odd. For instance:

"......all of the following conditions are met:

(1) The ampacity of the supply conductors shall be at least one-quarter of the ampacity of the supply overcurrent protection device.

(2) The supply conductors shall terminate in a single overcurrent protection device that will limit the load to the ampacity of the supply conductors."

Is the code referring to the same overcurrent protection device? Because if it is then it does'nt make sense. What would be the purpose of having (1) if it already states in (2) that the overcurrent protection device limits the load to the ampacity of the supply conductors? It seems that in (1) the supply conductors would not be protected if they were sized to at least one quarter the ampacity of the supply overcurrent device. It states that both conditions have to be met.
 
You know I was thinking the same thing but the NEC is just not clear in this particular section. If the supply conductor were a tap then the overcurrent protection device ahead of it on the feeder would be four times the ampacity of the supply conductor tap. Then the supply conductor would terminate into an overcurrent protection device sized to the ampacity of the tap(supply conductor).
 
erickench said:
(1) The ampacity of the supply conductors shall be at least one-quarter of the ampacity of the supply overcurrent protection device.

(2) The supply conductors shall terminate in a single overcurrent protection device that will limit the load to the ampacity of the supply conductors."

Is the code referring to the same overcurrent protection device? Because if it is then it does'nt make sense. What would be the purpose of having (1) if it already states in (2) that the overcurrent protection device limits the load to the ampacity of the supply conductors? It seems that in (1) the supply conductors would not be protected if they were sized to at least one quarter the ampacity of the supply overcurrent device. It states that both conditions have to be met.
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No, it refers to different devices. in (1), it is requiring that the line side protection not be more than four times the ampacity of the conductor.

In (2), they require the oc protection at the load end of the conductors not exceed the ampacity.

Very similar to various tap rules in Article 240, except adapted for stage use (not spliced, single conductors (usually type W or similar)).
 
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