AIC rating for service equipment

[tigerboy5602]

Hello all,

Looking for help in calculating the AIC rating to my service equipment. The formula I am using doesn't look right.

Transformer information.

3 Phase 120/208 on the secondary.

12 k transformer on pole. The AIC rating on the secondary of transformer 29760, with a 2 % resistance on the transformer.

The length from the transformer to my service equipment Is 115 ft.

400 amp 3 phase overhead service.

Would appreciate any help.

 

[Fitzdrew516]

I'm getting 14,766 and I'm using the C factor for conductors in non metallic conduit.

- Drew

 

[Fitzdrew516]

BTW I was using 600 kCMIL. Is this the size conductors you're using or are you paralleling sets?

 

[don_resqcapt19]

Bussmann has a free app that works very will for that type of calculation.

 

[topgone]

Hello all,

Looking for help in calculating the AIC rating to my service equipment. The formula I am using doesn't look right.

Transformer information.

3 Phase 120/208 on the secondary.

12 k transformer on pole. The AIC rating on the secondary of transformer 29760, with a 2 % resistance on the transformer.

The length from the transformer to my service equipment Is 115 ft.

400 amp 3 phase overhead service.

Would appreciate any help.

Somethings seems wrong with those numbers above.

You meant you have a 120kVA transformer on pole? Also, if the secondary is 208V 3-phase, that AIc rating is wrong (FL = 333A, Isc = 333/0.02 = 16654 A). ???

 

[tigerboy5602]

BTW I was using 600 kCMIL. Is this the size conductors you're using or are you paralleling sets?

I am using 500 kcmil. Not parallel

 

[tigerboy5602]

I'm getting 14,766 and I'm using the C factor for conductors in non metallic conduit.

- Drew

Thank you. It helps..

 

[don_resqcapt19]

Thank you. It helps..

The Bussmann app comes up with 15,285 for that based on the information you provided.

 

[victor.cherkashi]

You can use bussmann app on your smartphone

Sent from my Nexus 5 using Tapatalk

 

[kwired]

Hello all,

Looking for help in calculating the AIC rating to my service equipment. The formula I am using doesn't look right.

Transformer information.

3 Phase 120/208 on the secondary.

12 k transformer on pole. The AIC rating on the secondary of transformer 29760, with a 2 % resistance on the transformer.

The length from the transformer to my service equipment Is 115 ft.

400 amp 3 phase overhead service.

Would appreciate any help.

confused on info myself.

Guessing 12 k is a typing error? If that is 12 KVA that is not a very big transformer and may have a max fault current only around 1600 amps.

AIC is what rating you are looking for for your gear - in particular switches/breakers as those are "interrupting" devices. A transformer doesn't have a AIC rating but has a potentially available fault current, assuming you have been informed somehow that that available fault current at some specific point is 29760 - if so 2% impedance of transformer means nothing to you at this point as it was already factored in when they came up with the 29760, all you need from here is to figure out how much the resistance of conductors between that point of 29760 is and your gear you are trying to determine required AIC for.