## What Size Wire for 220 Volt 30 Amp? The Complete Guide
If you’re wiring a 220-volt, 30-amp circuit—for a dryer, water heater, or workshop outlet—getting the wire size right is critical for **safety, code compliance, and performance**. This guide breaks down exactly what you need.
### The Short Answer: **10-Gauge Copper Wire**
For a **220V, 30-amp circuit**, the correct wire size is **10 AWG copper** or **8 AWG aluminum**. Copper 10-gauge wire handles up to 30 amps at typical residential run lengths and is the standard choice for dryers, ranges, and similar appliances.
### **Why Wire Size Matters for a 30-Amp Circuit**
Undersized wire overheats, melts insulation, and can start a fire. The National Electrical Code (NEC) sets **ampacity ratings**—the maximum current a wire can safely carry. A 30-amp breaker demands wire rated for at least 30 amps.
**Key factors affecting wire choice:**
– **Voltage drop** over long distances
– **Insulation type** (NM-B, THHN, UF)
– **Ambient temperature** in the installation space
– **Conductor material**—copper vs. aluminum
For runs over 100 feet, you may need to bump up to **8 AWG copper** to prevent voltage drop. Follow the **80% rule**: never load a circuit beyond 80% of its capacity continuously.
### **Copper vs. Aluminum Wire**
**Copper** is the top recommendation—better conductivity, less expansion, easier terminations. **Aluminum** is cheaper but requires larger gauges and antioxidant paste at connections. For 30 amps, aluminum needs **8 AWG**.
If you’re also working on the plug end, our guide on what size wire for 220 volt 30 amp plug wiring walks you through each connection step safely.
### **Common 30-Amp, 220V Applications**
– **Electric dryers** — 10/3 NM-B with ground
– **Water heaters** — 10/2 or 10/3
– **Window AC units** — 10-gauge copper
– **Workshop tools & welders** — verify duty cycle
Each application may specify **2-wire** (hot, hot, ground) or **3-wire** (hot, hot, neutral, ground) depending on whether a neutral is needed for 120V components.
### **Wire Types You’ll See**
– **NM-B (Romex)** — indoor, dry locations
– **UF-B** — direct burial, underground
– **THHN/THWN** — conduit, wet or dry
– **SOOW** — portable cords
Choose based on installation environment, not just amperage.
### **FAQ**
**Can I use 12-gauge wire for a 30-amp circuit?**
No. 12 AWG is rated for 20 amps only. Using it on a 30-amp breaker is a fire hazard.
**Can I use 8-gauge wire instead of 10?**
Yes, upsizing is always safe and recommended for long runs.
**Do I need a neutral wire?**
Only if the appliance uses 120V components (like a dryer’s timer or light).
**What breaker size for 10-gauge copper?**
A 30-amp double-pole breaker.
### **Final Thoughts & Next Step**
**10-gauge copper wire** is your answer for a standard 220V, 30-amp circuit. Verify your local codes, account for distance, and always match