Point to Point Available Fault Current Calculator
By John Sokolik
So you have been awarded the job, a simple upgrade of electrical service from 200 to 400 amperes, you draw a riser diagram, the local utility has provided the transformer symmetrical fault current at the secondary terminals, now you need a way to calculate the available fault current at the service equipment for the AIR of the service main in order to get your building permit. This calculator provides a neat, clean, easy to print sheet for one, two or three part calculations. I suggest grabbing a pencil at doing the long hand, then plug those same values into the calculator and print it. Which one do you want to present the building official for permit?
[Click here to access the excel spreadsheet, or go to www.mikeholt.com, click on Free Stuff, and select Fault Current Calculator – Point-to-Point Method (Excel Spreadsheet 199KB)]
This calculator works two fold (1) When the symmetrical fault current at the secondary terminals is provided for you by the local power utility insert the value and move to ‘L’ for length (distance) of conductor from utility transformer to service equipment or main disconnect ‘N’ for number of conductors per phase and then select from the following drop down boxes, voltage and phase, conductor and raceway type, phase conductor AWG, neutral conductor AWG. Now you have calculated the Line to Line and Line to Neutral available fault currents (calculation does not include motor contributions) which may be added to future worksheets. (2) the second is where the transformer is customer owned, enter the kVA and the impedance (Z) to find the Isca. (Note: If you have a value in the Utility Fault Current field, right click the mouse and ‘Clear Contents’ before proceeding, see ‘Example Sheet’ tab at lower left corner of sheet.
A User was interested in using this in Mexico for a voltage of 220/127, another asked for the ability to insert for power factor for customer owned transformers in industrial applications and still another for 416/240 3Ø in Canada. So with the help of friends and users like you this calculator was developed.
Later the point-to-point was added to calculate for (1) Utility to service equipment (service entrance), (2) service equipment to panelboard (feeder), (3) panelboard to power outlet (branch circuit).
Use ‘Custom Views’ under the ‘View’ command to print any or all three point-to-point calcs.
John Sokolik has been in the electrical field for 35+ years in South Florida as an electrical apprentice, Journeyman, then Master Electrician, Vocational Instructor, Electrical Inspector/Plans Reviewer and Code Specialist, and AutoCAD proficient. For the last 4 years he operates a Florida Corporation and produces electrical design and permit documents, and designs build projects through as-built drawings for Electrical Contractors. He also works with several local Engineering firms providing from field observation reports to design. Let his experience work for you, in the State of Florida and Caribbean Islands; contact him for your electrical design needs:
John Sokolik, Inc.
Electrical Designer
P.O. Box 110802
Naples, FL 34108
Tel 239.594.2927
Fax 239.963.2311
jmp1jds@comcast.net
