Quick Hits

Episode 3: Branch-Circuit Short-Circuit, Ground-Fault & Overload Protection (Parts III & VI)

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: HVAC Short-Circuit & Overload Protection (Part 3) ⚡

The 175% rule, starting current exceptions, and thermal overload devices—let's review Parts III and VI of Article 440! 👇

SLIDE 2 (BRANCH-CIRCUIT SHORT-CIRCUIT & GROUND-FAULT PROTECTION)

Protecting Against Faults (440.22):

• Standard Sizing: Branch-circuit short-circuit and ground-fault protective devices must carry starting current, with a maximum setting/rating not exceeding 175 percent of the motor-compressor FLC (or branch-circuit selection current).

• Starting Current Exception: If 175% is insufficient for motor acceleration, the rating is permitted to be increased up to 225 percent.

• Listing Compliance: Always check nameplates for specific fuse or circuit breaker constraints (such as legacy HACR-type markings) per equipment listing instructions.

SLIDE 3 (MOTOR-COMPRESSOR OVERLOAD PROTECTION)

Preventing Dangerous Overheating (440.52):

• Separate Overload Relays: Separate overload relays responsive to compressor current must be selected to trip at not more than 140 percent of the FLC.

• Thermal Protectors: Integral thermal protectors or protective systems must restrict continuous current to no more than 156 percent of the marked FLC or selection current.

SLIDE 4 (WRAP-UP)

• 💡 Apprentice Pro-Tip: Always inspect the equipment nameplate to see whether fuses or specific circuit breakers are required—violating manufacturer listing instructions on HVAC short-circuit protection will fail inspection!

• 💬 Save this post for your next control panel diagnostic check!

• 🔗 More code breakdowns and study tools at www.JoshTheSparky.com

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