| Step 1a: |
When the Utility Fault Current is provided by the local utility enter the value here. Transformer KVA and impedance data is not required to continue. |
| Step 1b: |
If the Utility Fault Current is not provided, enter the transformer kVA and % impedance data. |
| Step 2: |
Select Primary, Secondary Voltage & Phase data from the dropdown boxes. |
| |
Transformer calculations will automatically populate selected fields based upon embedded formulas in the calculator. |
| Step 3: |
Select Conductor Type and Raceway Characteristics from the drop down box. |
| Step 4: |
Select conductor size between secondary main Molded Case Circuit Breaker (MCCB) and branch MCCB from AWG drop down box. |
| Step 5: |
Enter the length (feet) of one phase conductor between secondary main MCCB and branch MCCB or the length of conductor between the step-down transformer and panelboard with built-in secondary main MCCB and branch breakers. [Note: See NEC 240.21 regarding tap rules for transformer secondary conductors.] |
| Step 6: |
Enter the number of conductors per phase between secondary MCCB & branch MCCB. |
| Step 7: |
Select secondary transformer MCCB type from drop down box. |
| Step 8: |
Select the desired branch MCCB type from downstream branch breaker drop down box. |
| Step 9: |
Calculator will display coordination level and indicate if there is selective coordination between selected breakers. Note: Selected coordination is based on utilizing appropriate adjustable trip settings for all selected breakers. If the calculator indicates no selective coordination, then vary parameters such as conductor length, secondary, branch breakers to create a coordinated system. |
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