The battery in electric vehicles (EVs) must be charged by a specific charger that is not used for any other purpose. To install the EV charger, it is necessary to connect the charger to the electrical system of the building, which implies using the appropriate wiring to accommodate the charger’s electrical load. Choosing the correct wire gauge is essential to avoid excessive resistance and overheating of wire and to enable the charger to perform as it is designed. The following is a guide on how to decide on the correct wire size for use while installing an EV charger.
Energy Requirement of EV Chargers
The first thing that should be determined is the electrical load of the EV charger that will be installed.
The main factors that determine EV charger electrical load are:
– Charger power rating: Stated in kilowatts (kW), the charger power rating is the maximum amount of power that the given charger can provide to the battery of the EV. A higher power rating means shorter charge times. Level 2 chargers typically have power output ranging from 3. 3 kW to 19. 2 kW.
– Voltage rating: Level 2 EV chargers are typically powered through a supply of 208-240 volts. The voltage affects the current level and, therefore, influences the size of the wire needed.
– Duty cycle: Duty cycle means the ratio between the time a particular device performs at its optimal capacity and when it is inactive. EV chargers have an unbalanced current demand during charging sessions because chargers operate in an intermittent mode.
Find the Maximum Current Down
Once you know the charger’s power rating and voltage, you can calculate the maximum current (amps) it will draw from your home’s electrical system using this simple formula:
Charger current (amps) = Charger power (kilowatts) * 1000 / Charger voltage
For example, a common 9. 6 kW Level 2 charger configured for a 240-volt circuit will draw a maximum of 40 amps:
- 6 kW x 1000 / 240 volts = 40 amps
It is this maximum current draw that is used in the selection of the correct size of wiring.
Wire Type for EV Chargers
The basic options for wire type for EV charger installations are:
– Copper: Copper is the most preferred because it is conductive and typically has a long life span.
– Aluminium: It is cheaper than copper but not as durable or efficient in the transmission of power. It has to be connected using appropriate connectors that are compatible with aluminium wire.
Copper wire should be used for EV charger installation and is mandatory for some charger manufacturers. Flexible copper wire is more convenient to use than the solid core copper wire especially when fixing the cables.
NEC Minimum Wire Size Rules
The NEC has requirements of the minimum wire gauge depending on the expected electrical load. As per the specification referred above, the current demands that wires that supply EV chargers with 40A or less must comply with 125% of the charger’s maximum current.
Some key recommendations from NEC guidelines include:
– Up to 30 amp circuits: Cable with a minimum of 10 AWG copper wire should be used.
– 30-40 amp circuits: Ensure that you have at least 8 AWG copper wire
– Above 50 amp circuits: It is recommended that at least 6 AWG copper wire be used.
The 125% rule includes add-on thickness to the expected electrical current by demanding a minimum thickness of one hundred and twenty-five percent of the expected thickness.
Larger AWG (American Wire Gauge) for Long Distance
Suppose the distance between the charger position and the home electrical service panel is much larger. In that case, it is required to up the wire size because of the voltage drop typical for large wire runs. You can check the wire size charts to see the scaling up of the wire gauge depending on the length of that particular EV charging station.
Other Factors to Consider
Some additional factors that can influence wire size selection for an EV charger include:
– Future power needs: If more high-power devices are to be incorporated, choose wires according to future load carrying capacity.
– Ambient temperature: Wire ampacity decreases with the increase in temperature conditions and therefore there may be need to increase the size of the wire slightly.
– Number of bends: If wires have more than one bend then the allowable ampacity of the wire is affected and one has to use more wire.
Conclusion
It is, therefore, essential to put the correct wire size for an EV charger to guarantee that it provides the right and safe charging services. Charger electrical load rating estimation and the NEC guidelines as the minimum requirement standards are helpful when determining the copper wire size. If the length of the wire run is increased to a level where voltage drop becomes unbearable, it may call for an increase in wire gauge. It is recommended that an electrician be hired for the installation of EV supply wiring.
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