Quick Hits

Episode 2: Isolating Means, Backfeed Warnings & Grounding Switches (495.20 – 495.26)

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: High-Voltage Isolating & Backfeed Safety (Part 2) ⚡

Non-load-break switch rules, minimum air clearances, mandatory backfeed warning signs, and grounding switch interlocks—let's check Sections 495.20 through 495.26! 👇

SLIDE 2 (ISOLATING MEANS & BACKFEED WARNINGS)

Isolating Circuits Safely:

• Non-Load-Break Switches: Non-load-break isolating switches must be interlocked with an upstream interrupting device or field-marked with a warning against operating under load.

• Backfeed Signage: Where backfeed hazards exist, a permanent sign must state: DANGER — CONTACTS ON EITHER SIDE OF THIS DEVICE MAY BE ENERGIZED BY BACKFEED, accompanied by a single-line diagram.

SLIDE 3 (GROUNDING SWITCHES & AIR CLEARANCES)

Grounding Safety and Clearances:

• Grounding Switch Interlocks: Grounding switches must be interlocked with power sources so the disconnect must be open before moving the switch to the grounded position.

• Field-Fabricated Clearances: Field-fabricated installations must maintain minimum air separations between bare live parts and grounded surfaces in accordance with Table 495.24.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Always install mandatory backfeed warning signs on high-voltage disconnects where dual power sources can energize contacts from either side!

💬 Save this post for your next substation safety layout!

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