What is the Right Wire Size for a 4.8kW, 240V Range: #10 or #12?

Electrical Technology

How to Determine the Correct AWG Wire Size for a 4.8kW, 240V 1-Phase Electric Range According to NEC?

Since we’ve already covered various aspects of wire and cable sizing for different appliances, as we have already discussed the step-by-step calculation for determining the right wire size for wiring installation, sizing a circuit breaker, sizing the wire for 100 amp load circuits, and many more resources at the end of this article, we will now focus on the basic approach for determining the appropriate wire size for an 4.8kW electric range based on NEC codes and related tables.

Wire Size with Safety Factor

The first cramming approach by newbies to calculate wire size for ranges below 8kW is based on NEC Code 220-2 (safety factors) and refers to table 310-60, which, as we will see, is incorrect. Nevertheless, let’s explore how it works.

Let’s find the current in amperes in the circuit (using Ohm’s law)

I = P ÷ V

Where I is electric current in amperes, P is power in watts and V is voltage in volts.

I = 4800 W ÷ 240 V

I = 20 Amps.

As we can’t use the wire having ampacity of 20A for 20A load circuits. Let’s apply the safety factor of 1.25 (80% of the branch load should be connected to the rated ampacity of breaker or wire).

I = 20 A x 1.25

I = 25 Amps.

Based on conductor ampacity Table 310.15(B)(16), the right wire size for 25 Amps circuit is #10AWG at 60°C (140°F). Similarly, following the same rule as above, the rating of both the circuit breaker and associated 4 prongs connector/outlet (L14-30P Plug and L14-30R – Outlet) should not be less than 30A. Keep in mind that or a 4 wire system, a NEMA 14-50R outlet is recommended for higher-rated electric cookers, stoves, and ranges. You may use other types of plugs and outlets (such as 10-30R, 10-50R for old three wire system) when required/applicable.

This is all good for continuous load e.g. lighting, fans etc. Don’t stop here, move on to the next section for proper wire size based on the demand factor for non-continuous load.

Wire Size with Demand Factor

But wait a minute, the above case is different when it comes to non-continuous (non-simultaneous) loads, such as cooker ranges, water heaters, air conditioners, etc. In this scenario, another factor that affects the circuit current is known as the demand factor.

If the rating of electric ranges and other cooking appliances are less than 8-¾, the demand factor of 80% applies according to NEC Code 220.14, Table 220.55.

In this case, NEC-220.14 permits 220.55 and Table 220.55 to be used for calculating branch circuit loads for ranges. Similarly, NEC-220.11(C) permits using 220.55 for ranges for Branch Circuit load calculations. See note 3 of Table 220.55 too.

The demand for 1 unit in Column B of Table 220.55 is 80% of nameplate. This way

Wattage = 4800 W x 80% = 3840 W

Amps = Power ÷ Voltage

Amps = 3840 W ÷ 240 V

Amps = 16 A.

Additionally, if we apply safety factor of 1.25 to the calculated ampacity:

16 A x 1.25 = 20 Amps.

Now based on the 310.15(B)(16) table, the perfect wire size for 4.8kW (4800W), 240V single-phase electric range in #12AWG at 140°F (60°C).

The same rule applies to the associated miniature breaker, 4-prong plug (L14-20P) and outlet (L14-20R) used for an electric stove or range, i.e., the rating of the breaker should not be less than 20 amps.

Good to Know:

Using 12AWG wire on a 20A breaker is permitted under NEC – 422.10(A)(4).
NEC Code – 220.14 permits 220.55 and table 220.55 to be used for calculating branch circuit loads for ranges with 80% of demand factor.
According to the safety factor specified in NEC Code – 220-2, a 20A breaker is appropriate for a 16A circuit, and similarly, a 15A breaker is recommended for a 12A load circuit.
NEMA 14-50R outlet with associated 14-50P plug is recommended for higher-rated electric cookers, stoves, and ranges using 4 wires (two hot, neutral and ground wire). For old three wire system, you may use 10-30R, 11-30R, 10-50R.
For added safety and to accommodate future expansions, such as replacing the current range with a higher-rated one, it’s advisable to use #10AWG wire.