## 8.4 Voltage Drop Requirements

§130.5(c)

The voltage drop requirement, which has been clarified and revised in the 2016 update of the Energy Standards, is as follows:

Voltage drop of feeder + Voltage drop of branch circuit ≤ 5%

The maximum combined voltage drop on both installed feeder conductors and branch circuit conductors to the farthest connected load or outlet must not exceed five percent. This is the steady-state voltage drop under normal load conditions.

The voltage drop requirements of the following California Electrical Code (CEC) sections are exempted from the requirement of §130.5(c):

1. Article 647, Sensitive Electronic Equipment, Section 647.4 Wiring Methods.

2. Article 695, Fire Pump, Section 695.6, Power Wiring.

3. Article 695, Fire Pump, Section 695.7, Voltage Drop.

However, the informational note about voltage drop in Article 210, Branch Circuits, of the CEC is not part of the requirements of California Electrical Code, nor is the informational note about voltage drop in Article 215, Feeders.

Voltage drop represents energy lost as heat in the electrical conductors. The loss is called “I2R” (I-squared-R) loss, meaning that the loss is directly proportional to both the conductor resistance and to the current squared. Because of I2R loss, it is advantageous to distribute utilization power at the highest practical voltage to reduce the amount of current into each load.

Voltage drop losses are cumulative, so voltage drop in feeders and voltage drop in branch circuits add up to the load at the end of the branch circuit. Excessive voltage drop in the feeder conductors and branch circuit conductors can result in inefficient operation of electrical equipment.

Example 8-9

Do the following proposed designs meet the voltage drop requirement of §130.5(c)?

Answer:

All of the above proposed design scenarios meet the voltage drop requirement of §130.5(c), as the combined voltage drop of the feeder and the branch circuit does not exceed 5 percent.