Quick Hits

Episode 2: Stored Energy Discharge, Conductor Ampacity & OCP (460.6 – 460.9)

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: Capacitor Discharge & Conductors (Part 2) ⚡

Sensing residual voltage, the 135% ampacity rule, and overcurrent protection requirements—let's check Sections 460.6 through 460.9! 👇

SLIDE 2 (DISCHARGE OF STORED ENERGY)

Draining Residual Voltage (460.6):

• Discharge Time: Capacitors must feature means to reduce residual voltage to 50 volts, nominal, or less within 1 minute after being disconnected from the power source.

• Automatic Discharge: Discharge circuits must be permanently connected or automatic upon line voltage removal; manual switching means are strictly prohibited.

SLIDE 3 (CONDUCTOR AMPACITY & OVERCURRENT PROTECTION)

Sizing Wires and OCPDs:

• Conductor Ampacity: Capacitor circuit conductors must have an ampacity of not less than 135 percent of the capacitor's rated current (accounting for manufacturing tolerances and harmonic voltage variations).

• Overcurrent Protection: An OCPD must be provided in each ungrounded conductor for each capacitor bank and set as low as practicable.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Remember to size your capacitor supply conductors at 135% of the capacitor's rated current to handle manufacturing tolerances and waveform distortions!

💬 Save this post for your next industrial capacitor bank install!

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