Available Fault Current and SCCR Calculations

[jtgwynn]

While I am well aware that there are a few calculations and that one Excel spreadsheet available to me, I am having trouble wrapping my head around one thing.

I have a secondary panel fed from a larger MCP that is fed from a utility transformer. I know my available fault current and SCCR ratings at the MCP's main disconnect, but can I use any of that information to determine my fault current at the secondary panel?

I know the length and size of the feeder wire to the secondary panel, as well as the size of the fuses in its main disconnect. I am sure there is a relatively easy solution to this problem, but any help thrown my way would be much appreciated!

 

[petersonra]

While I am well aware that there are a few calculations and that one Excel spreadsheet available to me, I am having trouble wrapping my head around one thing.

I have a secondary panel fed from a larger MCP that is fed from a utility transformer. I know my available fault current and SCCR ratings at the MCP's main disconnect, but can I use any of that information to determine my fault current at the secondary panel?

I know the length and size of the feeder wire to the secondary panel, as well as the size of the fuses in its main disconnect. I am sure there is a relatively easy solution to this problem, but any help thrown my way would be much appreciated!

pretty much Ohms law. think of the conductors as resistors.

the fuse sizes do not matter.

 

[augie47]

Keep in mind, you overcurrent devices in your secondary panel can be sized in accordance with 240.86 (You can use the manufacturers listed series-rating charts)
It is not uncommon to find secondary panel breakers with a lower AIC rating due to their being series-rated with the supply device

 

[bob]

It would depend on the Excel program. If you can enter the available SC amps, do so. Then enter the cable size and
length. That's all there is to it. Check the program and determine what information is required. The SCCR ratings at the MCP's main disconnect has nothing to do with the calculations.