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AIC Calculations for Service Disconnects NEC 110.9

jar546

jar546

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During plan review, we require the AIC calculations for all permit applications that are replacing or installing a service disconnect. This includes Automatic Transfer Switches (ATS) for generators used as a service disconnect. This is covered under NEC 110.9 which we reference when we don't get the calculation and reject the permit.

Who else is doing this? This applies to residential and commercial. The commercial service disconnects go another step further requiring not only the calculation but a permanent label on the service disconnect showing the AIC rating and date of calculation.
 
steveray said:
Can you actually get it if they don't know the specifics on the transformer....?
Click to expand...
Yes, we get a letter from the POCO if the electrician does not know the specifics. If it is a pad-mounted transformer, there is enough information on the label for the electrician to figure out the available fault current at the secondary taps of the transformer. Most pole-mounted transformers have the KVA painted on them and the electrician can use a standard Z% to do the calculation.

The available fault current at the secondary taps fo the POCO transformer is just part 1 of the calculation. Part 2 takes into consideration the length of the service conductors from the secondary taps to the service disconnect, along with the type of wire, the size if it is in conduit, and what type of conduit.
 
steveray said:
Can you actually get it if they don't know the specifics on the transformer....?
Click to expand...
We recommend this app that they can use on their phone and send a PDF label right to their permit via email from the app.
IMG_6140.PNG

It will generate this PDF with the calculation:
 

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