Hello, I'm an expert in electrical systems and home appliances, and I'm here to help you with your question about sizing a breaker for a hot water heater.
When it comes to sizing a breaker for a hot water heater, there are several factors to consider. The first step is to determine the rated ampacity of the heater. This is the amount of electrical current the heater is designed to use, and it's typically listed on the unit itself or in the user manual.

Once you have the rated ampacity, the next step is to calculate the branch circuit requirements. According to the National Electrical Code (NEC), a water heater is considered a continuous load, which means the branch circuit must be able to handle a certain percentage above the heater's rated ampacity. This is to account for the continuous use of the heater over time.

In your case, you've mentioned a calculation that seems to be based on a 4500-watt heater operating on a 240-volt circuit. To find the rated ampacity, you would divide the wattage by the voltage:

\[ \text{Rated Ampacity} = \frac{\text{Wattage}}{\text{Voltage}} = \frac{4500}{240} = 18.75 \text{ amps} \]

Now, according to the NEC, you need to calculate 125% of this value to determine the minimum size of the branch circuit:

\[ 18.75 \text{ amps} \times 125\% = 23.4 \text{ amps} \]

This means that the branch circuit should be able to handle at least 23.4 amps. However, since standard breakers typically come in increments of 5 or 10 amps, you would round up to the nearest standard size. In this case, you would need a 25 or 30 amp circuit to meet the requirements.

It's important to note that the actual breaker size you choose should also take into account any other loads that will be on the same circuit. If there are other appliances or devices that will draw additional current, you'll need to ensure that the total load does not exceed the capacity of the breaker.

Additionally, it's always a good idea to consult with a licensed electrician when dealing with electrical installations, especially when it comes to something as critical as a water heater. They can provide professional advice tailored to your specific situation and ensure that all local codes and safety standards are met.

In summary, to size a breaker for a hot water heater, you need to:
1. Determine the rated ampacity of the heater.
2. Calculate the branch circuit requirements at 125% of the rated ampacity.
3. Choose a breaker size that is equal to or greater than the calculated branch circuit requirements, rounding up to the nearest standard size if necessary.
4. Consider any additional loads on the same circuit.
5. Consult with a professional electrician to ensure safety and compliance with local codes.

Remember, electrical work can be dangerous, and it's always best to have a qualified professional handle any installations or modifications to your electrical system.

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A water heater of this type is required to be considered a continuous load meaning that the branch circuit needs to be calculated at 125% of the heater's rated ampacity. 4500/240 = 18.75 amps, will work on a 20 amp OCPD but, 18.75*125% = 23.4 amps, requires a 25 or 30 amp circuit.Oct 2, 2012read more >>