A Common Error When Installing EV Chargers: Underestimating the Current Through the Main Breaker

When installing electric vehicle (EV) chargers, it is important to accurately assess the current that will be flowing through the main breaker of the panel feeding the EV chargers. 

One common error that can occur when installing EV chargers is underestimating the current through the main breaker. This can happen when the line-to-line current of the charger is used to calculate the current, rather than the line-to-neutral current.

To understand why this error occurs, it is helpful to consider the relationship between line-to-line and line-to-neutral current in a three phase system. In a three phase system, the line-to-neutral current is equal to the line-to-line current divided by the square root of three (√3). This means that the line-to-neutral current will always be higher than the line-to-line current.

For example, if an EV charger has a line-to-line current rating of 48 amps, the resulting line-to-neutral current will be 48 amps times √3, or approximately 83.1 amps. However, if the line-to-line current is used to calculate the current through the main breaker, the main breaker will be underestimated by approximately 40% .

To avoid this error, it is important to use the line-to-neutral current, rather than the line-to-line current, to calculate the current through the main breaker. This will ensure that the main breaker is properly sized to protect the electrical system and prevent overcurrents and fires.

In summary, when installing EV chargers, be sure to use the line-to-neutral current to calculate the current through the main breaker. This will help ensure that the main breaker is properly sized to protect the electrical system and prevent overcurrents and fires. Properly sizing the main breaker is an important safety measure that should not be overlooked when installing EV chargers.

If you have any questions or concerns about the current flowing through the main breaker when installing EV chargers, it is always a good idea to consult with an electrical engineering design firm. A qualified professional can help you assess your needs and ensure that your electrical system is safe and reliable.