NEC 240.4 (A)

[alixenos]

Hello,

240.4(A) of the NEC states that if power loss causes danger then overload protection is not required, but short circuit protection is.

My question is, how to provide a means of disconnect if overload protection is not required, or the two concepts are not related.

Thank you

 

[augie47]

Look at the NEC definition of an overload and you will note that circuits and equipment can withstand overloads for a period of time with little or no dangerous results whereas a ground-fault/short circuit can pose and immediate hazard damaging wiring & equipment t if not rectified.
The reference to a fire pump is a prime example. In the event the fire pump is need you are not too concerned about overload as the fire poses a more significant danger but, you do need protection from short-ciruits as they pose a more significant hazard.
To accomplish that result you select a device with a high enough rating that an overload will not cause it to open but still in a range that will protect against short circuits. I believe for a fire pump that setting is 600% of the pump current.

 

[alixenos]

Look at the NEC definition of an overload and you will note that circuits and equipment can withstand overloads for a period of time with little or no dangerous results whereas a ground-fault/short circuit can pose and immediate hazard damaging wiring & equipment t if not rectified.
The reference to a fire pump is a prime example. In the event the fire pump is need you are not too concerned about overload as the fire poses a more significant danger but, you do need protection from short-ciruits as they pose a more significant hazard.
To accomplish that result you select a device with a high enough rating that an overload will not cause it to open but still in a range that will protect against short circuits. I believe for a fire pump that setting is 600% of the pump current.

Thank you, thats helps.