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California Title 24 Voltage Drop Compliance

Tuesday, July 15th, 2014

Design Master Electrical can calculate and demonstrate compliance with the voltage drop requirements added to the 2013 version of the The Building Energy Efficiency Standards for California (commonly referred to as Title 24).

Section 8.4 of the 2013 Nonresidential Compliance Manual sets the following mandatory voltage drop limits:

  • Feeders can have a maximum of 2% voltage drop
  • Branch circuits can have a maximum of 3% voltage drop

These values are different from what is specified in NEC 210.19(A)(1) FPN No. 4 and NEC 215.2(A)(3) FPN No. 2. The NEC sets a maximum value of 3% for both feeders and branch circuits, with a total maximum of 5% for both.

Use the DM Electrical->One-Line Schedules->Insert Voltage Drop Schedule command to insert a schedule listing the feeder and branch circuit voltage drops in your project.

Set the Highlight Voltage Drops field to Yes, Feeder > 2%, Branch Circuit >3% to highlight any voltage drops that exceed the maximum values set in the 2013 Standard.

Set the Circuits to Display field to one of the All selections to display the voltage drop on all of the circuits on your panels.

  • All: All circuits will be displayed, including spaces and spares.
  • All with Load: All circuits with a load will be displayed. Any circuits with a fixed load and no other devices connected will be displayed, but the voltage drop will be listed as 0%.
  • All > 0: All circuits with a voltage drop greater than 0% will be displayed. Spaces and spares will not be listed, and circuits with fixed loads and no other devices connected will not be listed.

Use the DM Electrical->One-Line Devices->Panels command to change the size of any feeders that exceed the maximum voltage drop.

Use the DM Electrical->Circuiting and Homeruns->Circuits command to change the size of any branch circuits that exceed the maximum voltage drop.

Calculations

Section 8.4.2 lists three different options for calculating voltage drop in branch circuits. Design Master Electrical always uses option (a). The other calculation methods are simplifications that are allowed when doing the calculations by hand.

Section 8.4.4.C lists two options for calculating voltage drop in feeders. Design Master Electrical always uses the first. The calculation based upon 80% of the  rated ampacity is a simplification that is allowed when doing the calculation by hand. Use the Future Demand load on the panel if you need to account for additional load from spaces or spares.

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