A 5,500-watt water heater rated 208 or 240V will need 10 AWG size and a circuit breaker capacity of 40A for 208V or 35A because that a 240V rating. 

Water heater voltage ratings and also how they affect wire and circuit breaker capacity

Your water heater might have any kind of of the voltage ratings 120, 208, 277, or 480V. 

The present rating have the right to be found from the formula: 

Water heater strength rating (watts) / voltage (volts).

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From the formula, a lower voltage outcomes in a greater rated current and subsequently might require a lower wire gauge and greater circuit breaker rating.

Always confirm first whether the water heater capacity is accessible for the desired voltage rating (120, 208, 277, or 480V) together this influence your choice of wire and also circuit breaker size.

How to calculation water heater wire and also breaker size

Water heater wire size

A 5,500 W heater rated 240V has a rated present of 5500/240 = 22.91 amps. This is the heater’s minimum existing rating.

Using the wire amp rating come gauge calculator, the recommended cable gauge is 10 AWG.

Water heater circuit breaker size

To occupational out the encourage breaker size, allows refer to the excerpt from NEC 2017 below.

(E) solitary Non–Motor-Operated Appliance. If the branch circuit supplies a single non–motor-operated appliance, the rating of overcurrent protection shall comply through the following:

(1) not exceed that marked on the appliance.

(2) no exceed 20 amperes if the overcurrent security rating is not significant and the appliance is rated 13.3 amperes or less; or

(3) not exceed 150 percent the the appliance rated present if the overcurrent defense rating is not significant and the appliance is rated end 13.3 amperes.

Where 150 percent that the appliance rating does no correspond to a conventional overcurrent device ampere rating, the next higher standard rating shall be permitted.

Since the heater is rated more than 13.3 amps (22.91 A >13.3A), climate the circuit breaker rating = 22.91 x 150% =34.36 Amps. The next standard circuit breaker is 35 Amps.

Therefore a 5,500W heater rated 240V requirements 10 AWG cable size and a circuit breaker that 35A.

The table below shows indicative cable gauge and also circuit breaker ratings because that selected water heater power ratings.

Note: This is a overview only. Always consults a default professional.

No.Water heater aspect power (W)Water heater voltage* (V)Minimum wire gauge (AWG)Circuit breaker (A)
11,4401201520
21,5001201520
32,0002081020
42,5002081520
53,0002401520
64,0002402025
74,5002402030
85,0002402535

*Voltage ratings because that the various heaters may vary. Confirm availability of the water heater in the wanted voltage.

**Assumes the the circuit breaker rating is no specified. Multiply rated present by 150% come be code compliant if rated present is an ext than 13.3 A. If rated existing is less than 13.3A, set to 20 A (NEC, 2017)

What size of wire and breaker because that 30, 40 and also 50 gallon water heater?
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The encourage wire and breaker size will be established by her heater’s power rating and also voltage.

For 30 gallon (2,000W, 120V), 40 gallon (5,500V, 240V), 50 gallon (4,500W, 240V), the minimum wire sizes for your water heaters would be 20, 25, and 20A respectively.

While the corresponding circuit breaker capacities would be 25A, 35A, and also 30A respectively.

To uncover the wire and circuit breaker rating, first, examine with the manufacturer or technological specifications hand-operated for the current and also circuit breaker rating because that that details model that heater.

Note: that is feasible for waters with different capacities to have the same heater aspect power rating.

For example, both a 40 and 50-gallon water heater may have actually a 4,500 heater element.

The table listed below shows selected water heater capacities through their corresponding heater facet power ratings.

Always consult her water heater’s manual.

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No.Water heater volume (gallons)Water heater facet power rating (watts)
1121,500
2191,800
3302,000
4404,500
5504,500

You can then usage the water heater facet power rating to occupational out the wire and also breaker size that is ideal for her water heater. 

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