Air-Conditioning & Refrigerating Equipment

Article 440 builds on Article 430 for the hermetic motor-compressors inside air conditioners, heat pumps and refrigeration equipment. Because these motors are sealed in the refrigerant system, they carry their own nameplate ratings — rated-load amps (RLA), minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP) — and the electrician sizes conductors and protection directly from those numbers.

The article requires a disconnecting means within sight of the equipment, addresses the combined load of the compressor plus fan motors, and coordinates with room air-conditioner and branch-circuit rules. For most field work, the golden rule is simple: follow the nameplate — MCA sets your wire, MOCP caps your breaker.

When it applies

Air-conditioning and refrigeration equipment run on hermetic motor-compressors, and Article 440 sizes their circuits from nameplate values rather than horsepower. You use figures like the rated-load amps and the minimum circuit ampacity to pick the conductors, and the maximum overcurrent protection to size the breaker or fuses and the disconnect.

Common mistakes

• Sizing the wire to the breaker instead of the nameplate MCA, then coming up short.
• Exceeding the maximum fuse or breaker size the nameplate allows.
• Placing the disconnect out of sight of the unit where it cannot be readily reached.

In the field

I size straight off the data plate: conductors to the MCA, protection at or below the max marked, and a disconnect within sight of the condenser. The nameplate is the law on these units, not the rule of thumb.