Work with electrical circuit paths and wire sizing

Step-by-step guide

Understand voltage drop and wire size in a circuit.

1. Open the project E01_01.rvt. Ensure the current view is Lighting > Floor Plans > 1 – Lighting.
2. Type “ES” on the keyboard to access the electrical settings for this project. Note the values for maximum voltage drop for wire sizing in branch and feeder circuits.
3. Click OK.

4. In the View tab of the ribbon, create a new schedule for electrical circuits by selecting Schedule/Quantities from the Schedules menu.
5. Name the schedule “Branch Circuits”.
6. In the Schedule Properties dialog box, from the Available fields list, add Circuit Number, Length, Voltage, and Voltage Drop to the Scheduled fields list.

7. In the Filter tab of the Schedule Properties, next to Filter by, select Voltage, select equals, and then select 120V.
8. Click OK to close the window and create the schedule.

To create a calculated parameter within the schedule to display the voltage drop as a percentage:

9. Click Edit in the Fields parameter of the schedule.
10. Click Add Calculated Parameter.
11. Name the calculated parameter “% Voltage Drop”.
12. Set the Discipline to Common.
13. Set the Type to Number.
14. Enter the Formula: Voltage Drop/Voltage*100
15. Click OK to close the dialog box.

16. Change the view to 1 – Lighting.
17. Use the TAB key and the mouse button to highlight and select the hallway circuit.
18. Review the wire size in the circuit Properties.

19. Tile the open views to display the floor plan and schedule.
20. Use the method in step 17 to highlight and select the hallway circuit.

21. In the Modify | Electrical Circuits tab of the ribbon, click Edit Circuit.
22. Select the lighting fixtures in the bottom left corner of the floor plan to add them to the hallway circuit.

23. Read and close the warning message.
24. Review the calculated values in the schedule and note the increase in % Voltage drop for circuit 3.

25. Highlight and select the modified hallway circuit in the view 1 – Lighting, and then in Properties, note the unchanged wire size.

Now, edit the circuit path to see the effect on circuit length and wire size:

26. With the hallway circuit still selected, click Edit Path in the ribbon.
27. In the Path Mode drop-down, select All Devices, and note the change to circuit length.
28. Review the voltage drop value in the schedule, and the wire size in the circuit properties AWG12.

29. Edit the path offset to 10' 0", and note that there is no change in the values for voltage drop in the schedule and wire size in the circuit properties.
30. Click Finish Editing Path.
31. Select the hallway circuit using the method in step 17.

32. Click Edit Circuit.
33. Add a lighting fixture from any other circuit.
34. Ignore and close the warning message.
35. Review the circuit properties, noticing the increased wire size due to the voltage drop from this branch circuit having exceeded 2%.

36. In the schedule, review the voltage drop for circuit 3, which is now reduced due to the increased wire size.

37. Save the project.