AWG stands for American Wire Gauge, the standard measurement system for electrical conductor diameters used throughout North America. AWG numbers range from 0000 (thickest) to 40 (thinnest), with each step representing a specific cross-sectional area measured in circular mils. HVAC systems commonly use AWG sizes from 18 (control circuits) to 1/0 (major power distribution).
Technical Details
An 18 AWG conductor has 1,624 circular mils area, while 12 AWG measures 6,530 circular mils. Wire diameter increases approximately 10% per AWG step smaller (lower number). Resistance decreases as AWG decreases: 18 AWG copper at 68°F measures 6.51 ohms per 1,000 feet, while 12 AWG measures only 1.62 ohms per 1,000 feet. Temperature ratings affect ampacity; 14 AWG at 60°C carries 15 amps, at 75°C carries 20 amps.
Practical Significance in HVAC
AWG sizing follows NEC ampacity tables to prevent overheating and fire hazards. Undersized conductors create voltage drops that reduce compressor torque and efficiency. HVAC control circuits typically use 18 AWG for low-voltage thermostats, while main power feeds to outdoor units require 10 AWG or larger depending on equipment specifications and distance from service panel.