NEC Required Fault Current Calculations

[Sparky1981]

I have an inspector who wants the fault current calculation for a timeclock mounted next to a panel to verify its AIC rating. Never run calculations for branch circuits before and cannot find a code reference listing what is required. Is there one?

 

[tom baker]

Is this a service panel or feeder panel?
If a service panel is it labeled with the available fault current?
And for that panel what is the AIC ratings of the breakers?
Perhaps the inspector saw breakers with a 22 KAIC rating and was concerned about the time clock
Interesting question.

 

[David Castor]

NEC says that devices have to applied within their ratings, and that includes short circuit current.

 

[Sparky1981]

Is this a service panel or feeder panel?
If a service panel is it labeled with the available fault current?
And for that panel what is the AIC ratings of the breakers?
Perhaps the inspector saw breakers with a 22 KAIC rating and was concerned about the time clock
Interesting question.

Thats exactly what it is. The panel has an available of 13,500. The time clock is only rated 5,000. This would be considered a branch circuit. So where does this application end? I have NEVER ran a fault current calculation for a branch circuit, with the exception of some mechanical equipment until today.

 

[don_resqcapt19]

Thats exactly what it is. The panel has an available of 13,500. The time clock is only rated 5,000. This would be considered a branch circuit. So where does this application end? I have NEVER ran a fault current calculation for a branch circuit, with the exception of some mechanical equipment until today.

It doesn't end until the end of the last branch circuit. In most cases the small size and length of the branch circuit conductors results in a substantial reduction in the available fault current at the load end. However were there is equipment very close to the main panel, there can be issues.

 

[electrofelon]

I have an inspector who wants the fault current calculation for a timeclock mounted next to a panel to verify its AIC rating. Never run calculations for branch circuits before and cannot find a code reference listing what is required. Is there one?

See 110.9 and 110.10. basically everything theoretically needs to be evaluated for suitable AIC and SCCR. This is one of those things that use to be mostly ignored, but has gradually become more and more emphasized and enforced.

 

[synchro]

This has some relevant info:

https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=411.0

 

[ron]

Thats exactly what it is. The panel has an available of 13,500. The time clock is only rated 5,000. This would be considered a branch circuit. So where does this application end? I have NEVER ran a fault current calculation for a branch circuit, with the exception of some mechanical equipment until today.

Use an online calculator such as http://faultcurrentcalculator.agili...ml?ver=1.5&noCache=1679866526620#phase-select
and use 13500A as the incoming and take a guess at the branch circuit length and wire size, so it will tell you the available at the equipment.