What breaker does a 4500 watt water heater need?

4500 watts at 240 volts draws 18.75 amps. As a continuous load under NEC 422.13 it needs 125 percent, or 23.4 amps, so a 25 amp breaker minimum. A 30 amp breaker with 10 AWG copper is permitted by 422.11(E)(3) and is the common installation.

Can I use 12 AWG wire for an electric water heater?

Not for a standard 4500 watt element, which requires 10 AWG on a 25 or 30 amp circuit. Only smaller 3800 watt or lower elements can qualify for a 20 amp circuit, and the nameplate governs.

What Size Breaker Do I Need for a 40 Gallon Electric Water Heater?

A user asked the app what breaker a 40 gallon electric water heater takes. The standard residential unit has a 4500 watt element at 240 volts, which draws 18.75 amps. NEC 2023 422.13 treats any storage water heater of 120 gallons or less as a continuous load, so the branch circuit must be rated at least 125 percent of that current: 18.75 times 1.25 is 23.4 amps. The minimum legal breaker is therefore 25 amps, and the everyday field standard is a 30 amp two pole breaker on 10 AWG copper.

Why 30 amp is the common answer

422.11(E)(3) lets the overcurrent device for a nonmotor appliance run up to 150 percent of the rated current when the 125 percent value does not match a standard size. For 18.75 amps that allows up to 28.1, rounded into a 30 amp breaker under the next standard size rule. Since 10 AWG copper is rated 30 amps at 60 degrees and 25 amp two pole breakers are special order in many panels, 30 amps with 10/2 NM is the sensible default. A 25 amp breaker with 10 AWG is equally compliant. What is not compliant is 12 AWG on the typical 4500 watt unit; save that for the rare 3800 watt element, and check the nameplate every time because 5500 watt heaters need the math rerun.

Disconnect and protection details

The water heater needs a disconnecting means per 422.31(B). If the panel breaker is within sight of the heater it qualifies; otherwise install a lockable breaker device that stays on the panel, or a local disconnect at the unit. As of the 2023 cycle, 422.5 does not require GFCI for a hardwired storage water heater in most locations, but some state amendments differ, so check your adopted code. Bond the circuit ground to the heater and never rely on the water pipe as the grounding path.

Heat pump water heaters are different

Hybrid heat pump units often carry a nameplate around 15 to 25 amps with specific breaker instructions. The nameplate and 110.3(B) win over the generic math, so follow the marked maximum overcurrent protection.

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