Quick Hits

Episode 2: Supply-Side Wiring Methods & Transformer Leads (725.127)

SLIDE 1 (HOOK / COVER) ⚡ NEC Quick Hit: Supply-Side Wiring & Transformer Rules (Part 2) ⚡ 

When does standard Chapter 3 line-voltage wiring stop, and when does low-voltage Article 725 take over? Let's look at the supply-side rules for Class 2 and 3 power sources! 👇

SLIDE 2 (SUPPLY-SIDE vs. LOAD-SIDE RULES) Where Do Chapters 1–4 Apply?

• Supply Side: Conductors, transformers, and overcurrent devices on the supply side of a Class 2 or Class 3 power source must be installed in accordance with standard Chapters 1 through 4 wiring methods.

• Load Side: Once you cross the power source or OCPD onto the secondary side, Article 725 installation rules take over.

SLIDE 3 (THE TRANSFORMER LEAD EXCEPTION) Short Transformer Input Leads:

• Input leads feeding a Class 2/3 transformer are permitted to be smaller than 14 AWG (down to 18 AWG).

• Conditions: They must not be over 305 mm (12 in.) long and must be protected by an overcurrent protective device rated at 20 amperes or less.

SLIDE 4 (WRAP-UP) 💡 Apprentice Pro-Tip: 

Never run Class 2 and Class 3 low-voltage cables in the same raceway, cable tray, or enclosure as electric light, power, and Class 1 conductors unless specifically permitted by Article 722 separation rules!

💬 Save this post for your next transformer wiring and control panel layout! 🔗 

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