Arizona SCCR new code adoption

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Bigdogclancy

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Iowa
Hey, I need to find out if Arizona has passed a requirement for all power installations to provide sufficient current limitiing fuses so that all downstream circuits are protected for 5KA SCCR rating. Just got this word back from one of our field sales persons in the area. Anybody enlighten me on this. Thanks,
Brent Clancy
 
The provision of current limiting fuses will not reduce downstream current to any particular amount.
Dynamic impedance is why the code required tested combinations unless a PE is willing to create a series combination.
 
In addition to preventing the use of most circuit breakers (240.86), other problems are:

1) Most 400A and larger current limiting fuses do not begin to limit fault currents much below 10kA.

2) How would 110.9 and 110.10 be enforced

3) This would be a forced series combination rating, which 110.22 requires to be approved by the manufacturer of the equipment.
 
arizona SCCR

arizona SCCR

i called the commercial division of the Arizona inspection dept. The answer I received from them was what i thought was suppose to be correct. The 2005 NEC code is what the state is enforcing. The additon of whatever means to limit the SCCR downstream current to 5KA is only applicable when needed. In other words if the current available exceeds the rating of the cabinet then protection in the feeder circuits has to be provided. There is no mandated provision of fusing to limits of 5KA minimums. I appreciate all that chimed in. Sorry I didnt sort out the initial information better at the beginning.
Brent Clancy
 
Big Dog,
My point was that it wouldn't be possible anyway.
You cannot just install a current limiting fuse or current limit circuit breaker and know that the downstream distribution would see less than 5,000A short circuit current or any such number during a fault.
The impedance of all the downstream equipment, as the breakers and fuses open during a fault will not let that happen.
 
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