What Size Wire for Central Air Conditioner? — Complete Wiring Guide
A Central Air Conditioner requires 10 AWG copper with a 30A double-pole (check MCA) on a 240V dedicated circuit. Here is the complete NEC-compliant wiring guide.
Central Air Conditioner Wiring Details
Central AC units are sized differently from standard appliances. Instead of simple wattage, look for two values on the unit nameplate: MCA (Minimum Circuit Ampacity) and MOP (Maximum Overcurrent Protection). MCA determines your minimum wire size, and MOP determines your maximum breaker size. A typical 3-ton residential AC has MCA of 19-22A and MOP of 30-40A. Use wire sized for the MCA with a breaker at or below the MOP. For most 2-5 ton residential units, this means 10 AWG wire with a 30A or 40A breaker.
NEC Code Reference
The wiring requirements for a Central Air Conditioner are governed by NEC Article 440. Always check the appliance nameplate for specific electrical requirements — the manufacturer's specifications take precedence over general guidelines. Your local AHJ (Authority Having Jurisdiction) may have additional requirements beyond the NEC.
Pro Tip
Never size AC wiring from BTU ratings alone. A 36,000 BTU (3-ton) unit might have an MCA of 19A or 25A depending on efficiency (SEER). Always use the nameplate MCA. If the AC and furnace/air handler share a circuit for the blower motor, the combined load determines wire size.
Disclaimer: This guide is for reference only. All electrical work must be performed by or verified by a licensed electrician. Local codes may differ from NEC.