Service AIC ratings

[Goroon]

:-?The panel is protected For 27KAIC with your fuses, Yes, But , if the fault is down stream of the panel?.
AIC ratings are determined by Resistance (wire), Distance and available ?Current? at the point of fault.
Single phase faults are higher than Phase to Phase ?and on and on?.. A fault down stream of the 10 KAIC breakers still has to pass through the 10 KAIC breaker, reduced to new 15 KAIC Levels based on Distance? , metal duct? In Or near the panel after the breaker at 22 KAIC..

 

[jim dungar]

:-?The panel is protected For 27KAIC with your fuses, Yes, But , if the fault is down stream of the panel?.
AIC ratings are determined by Resistance (wire), Distance and available ?Current? at the point of fault.
Single phase faults are higher than Phase to Phase ?and on and on?.. A fault down stream of the 10 KAIC breakers still has to pass through the 10 KAIC breaker, reduced to new 15 KAIC Levels based on Distance? , metal duct? In Or near the panel after the breaker at 22 KAIC..

According to the manufacturer's information the OP fuses do not series rate with the branch breakers.

AIC ratings of devices comes from testing by the manufacturer. AIC ratings need to be larger than the SCA (short circuit, available) which are calculated at the point of the fault.

Single phase faults are not higher than three phase bolted faults. Single phase fault interruption maybe more severe than three phase interruption (the arc is only being broken by 1 contact rather then 2 or 3).

 

[Ken In NJ]

Update

Update

This is a copy of the e-mail I received today from the engineer ..

To follow up on our phone conversation this morning, the AIC rating listed on our plans on the panel schedule for panel ?A? is 22,000 AIC. This value was determined with calculations using a feeder length of approximately 80?-0?. This yielded an AIC rating at Panel ?A? of approx: 11,380 AIC. This value is significantly increased the shorter the feeder length becomes. Locating the panel 3? away from the service disconnect would yield an AIC rating of roughly 26,000 AIC. The closer that panel ?A? is to the service disconnect, the closer the AIC rating would become to the rating of the service disconnect (which 27,778 AIC stated by the local utility).



The feeder length for panel ?A? would have to be approximately 100?-0? away from the service disconnect location to achieve an AIC rating of 10,000 AIC.

I "we" are still confused .. so move the sub-panel 100' away from the service disconnect ? The tenant space is small .. getting the panel 100' away would be crazy .. maybe some s loops in the conduit ?

 

[ron]

So determine the length of the conductors and pick an AIC rating (fully rated or series) higher than his calculated value.

It is nice that he is giving you an option as he could have arbitrarily chosen 42kAIC or 65kAIC to CHA (cover his a-s). It is done that way very often.

 

[jim dungar]

I "we" are still confused .. so move the sub-panel 100' away from the service disconnect ? The tenant space is small .. getting the panel 100' away would be crazy .. maybe some s loops in the conduit ?

Did your engineer address the issue of using a series rated fuse-breaker combination?


I am sorry to see that your engineer confuses the specific terms AIC and SCA. Please try not to fall into that bad habit yourself. AIC are ratings unique to protective devices that intended to interrupt fault current. These have been established by testing and are covered in the NEC by 110.9. Devices that are not intended to interrupt fault currents have an SCCR (short circuit current rating), also called withstand rating, these are addressed in NEC 110.10. The amount of fault current in a system is called SCA (short circuit amps). Yes all of these terms are interrelated, but they are not interchangeable. When an engineer tells me what AIC or SCCR is required, I know nothing about what fault the system can provide; but when I am told the system SCA, I can figure out what equipment is needed.