Let's break down the calculations and code compliance for your forklift charger installation.1. Current Calculation

Your current calculation seems to be on the right track but needs adjustment for your service voltage. The key is to use the actual voltage you're providing, not a nominal one.

Apparent Power (kVA)

4.7 kVA

Service Voltage (V)

230V, 3-phase

Power Factor

The charger's power factor is extremely important. Since the kVA rating is given, and not a kW rating, we

must assume a power factor of less than 1. If you can find the actual power factor, that would be best! If it's not available, a power factor of 0.8 is a reasonably conservative assumption for many industrial loads. Without a power factor, your calculation will be inaccurate.Revised Current Calculation (using a power factor of 0.8 as an example)


Real Power (kW)

4.7 kVA 0.8 = 3.76 kW2.

Amperes (I)

I = (kW x 1000) / (V x √3) = (3.76 kW x 1000) / (230V x 1.732) = 9.43A

Important

Find the power factor for the charger! A different power factor will significantly change the current. If the charger only lists kVA, assume the worst-case power factor (as low as 0.7, but a good starting point is 0.8). If the charger lists kW (real power), use that instead of kVA, and the power factor becomes 1.

2. Wire Size and Overcurrent Protection (AWG #12 THHN and 30A Breaker)



AWG #12 THHN Ampacity

AWG #12 THHN is typically rated for 30 amps in most applications. However, derating factors MUST be considered. Derating can be necessary for:

High Ambient Temperature

If the wire is installed in a hot environment, its ampacity decreases.

Conduit Fill

If you have multiple current-carrying conductors in the same conduit, their ampacity decreases. This is a very likely scenario, as you'll have three phase wires and a ground wire.

NEC (National Electrical Code) Compliance



125% Rule (Continuous Load)

Forklift chargers are generally considered continuous loads (operate for 3 hours or more at a time). The NEC requires that the overcurrent protection (breaker) be rated for at least 125% of the continuous load current.

If your actual calculated current is 9.43A 9.43A 1.25 = 11.79A. AWG #12 is acceptable, but ONLY if you are following NEC and THHN are rated for 30A ampacity. If your actual calculated current, based on a lower power factor, is significantly higher (e.g., closer to 13.56A or higher with a very low power factor), AWG #12 may not be sufficient, especially after derating for ambient temperature and conduit fill. You would need to use a larger wire size, like AWG #10 THHN. Overcurrent Protection

A 30A breaker is likely too large if your calculated current is close to the 9.43A. Ideally, the breaker should be sized closer to 125% of the calculated continuous current. If your continuous load is 11.79A, you should be using a 15A Breaker.

In summary, for AWG #12 THHN and 30A breaker



Potentially Compliant, BUT very borderline and requires further investigation! It depends on your actual calculated current after accounting for the power factor, and derating factors for ambient temperature and conduit fill. Get a confirmed FLA (Full Load Ampere) or actual measured amp draw reading from the forklift charger. This is the best data. Evaluate your installation environment

How hot will it be? How many other wires will be in the conduit? Use NEC tables (Table 310.15(B)(2)(a) for ambient temperature, Table 310.15(B)(3)(a) for conduit fill) to determine derating factors.

A 20A breaker might be a more suitable and compliant choice, IF your calculations after derating allow for it.3. Disconnect Switch (Isolator)



Sizing

The disconnect switch (isolator) must be rated for at least the circuit's voltage and amperage.

Voltage Rating

It must be rated for at least 240V (since you have a 230V system). A 240V or higher rating is standard.

Amperage Rating

It must be rated for at least the calculated continuous current (plus any applicable derating). Since you are using a 30A breaker, you will need to use a 30A isolator.

Type

Ensure the disconnect switch is suitable for the environment (e.g., NEMA rating for dust, water, etc.). A non-fused disconnect is usually adequate for this application, since the breaker provides overcurrent protection.

Example

Let's say you determine your calculated load current, after accounting for a power factor of 0.8, is 9.43A and you have moderate conduit fill (derating factor of 0.8).
1.

Derated Ampacity of AWG #12 THHN

30A 0.8 = 24A (assuming derating).
2.

125% Continuous Load

9.43A 1.25 = 11.79A.
3.

Wire Size Check

The derated ampacity of AWG #12 (24A) is greater than the 125% continuous load (11.79A). This appears compliant, but is marginal.* It's still better to use a 20A breaker!4.

Breaker Size

A 30A breaker is excessive. A 15A breaker is recommended.5.

Disconnect Switch

A 30A, 240V non-fused disconnect switch would be appropriate.

Recommendations


Crucially, get the Power Factor (PF) from the charger's documentation or manufacturer.2. Recalculate the current based on the actual power factor and your 230V service voltage.3. Evaluate the installation environment and apply derating factors (ambient temperature, conduit fill).4. Verify that AWG #12 THHN (after derating) has sufficient ampacity for the 125% continuous load.5. Consider using AWG #10 THHN for additional safety margin, especially if derating is significant.6. Select a breaker that is sized appropriately for the load (closest standard size above 125% of the continuous current).7. Choose a disconnect switch with a voltage and amperage rating suitable for the circuit.8. A qualified electrician should perform the final installation and verification.Disclaimer: I am an AI assistant and cannot provide legally binding electrical advice. All installations must comply with the NEC and local electrical codes. Consult a licensed electrician for your specific application. Flag for review