Okay, let's break this down step-by-step to determine the correct branch circuit sizing for your 12.6kW range according to the NEC.

Understanding the NEC Sections Involved NEC 220.55 (Table 220.55 and Notes)

This table is used to calculate the demand load for ranges, not necessarily the branch circuit directly, but it's a critical starting point. Note 5 specifically permits its use to size the branch circuit.

NEC 210.19(A)(3)

This section sets the minimum ampacity for range branch circuits.

NEC 210.20

This section deals with overcurrent protection (breakers/fuses).

NEC 310.16

This is the ampacity table for conductors (like THHN).

Your Proposed Calculation and Analysis

You're proposing to use Note 1 of Table 220.55 and Column C to determine the demand load for a single range, then size the branch circuit based on that demand.Here's a breakdown of your logic:1. Base Load

Using Column C (one appliance), the base demand is 8 kW.2.

Adjustment for Over 12 kW

Note 1 states to add 5% to the base demand for each kW or major fraction thereof by which the range rating exceeds 12 kW. Your range is 12.6 kW, which is 0.6 kW over 12 kW. Therefore, you add 5% of the 8kW base. 5% of 8 kW = 0.05 8 kW = 0.4 kW3.

Total Demand Load

8 kW (base) + 0.4 kW (adjustment) = 8.4 kW4.

Current Calculation

8400 W / 240 V = 35 Amps

The Key Issue: NEC 210.19(A)(3) and Minimum Branch Circuit Rating

You correctly identified NEC 210.19(A)(3), which says: "Branch-circuit conductors having an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 8 3/4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes."Analysis and Conclusion The Demand Calculation is Likely Correct

Your calculation using Note 1 and Column C of Table 220.55 is likely a valid method for determining the demand load of the range. However,

the demand load is not the only factor. NEC 210.19(A)(3) Controls

Because your range is 12.6 kW (well over 8 3/4 kW),

NEC 210.19(A)(3) requires a minimum 40-amp branch circuit. Conductor Size

Since you need a 40-amp branch circuit, you must use a conductor with an ampacity of at least 40 amps. 8 AWG THHN typically has an ampacity of 55 amps at 75 degrees Celsius (check the specific ampacity table you're using).

Therefore, 8 AWG THHN is suitable for the conductors. Overcurrent Protection

You will need a 40-amp breaker, complying with NEC 210.20.

Answer

Yes, you are correct to put that 12.6 kw range on a 40 amp breaker with 8 awg thhn

IF the following conditions are met:1. The ampacity of the 8 AWG THHN wire at the termination temperature (usually 75°C) is 40 amps or greater according to NEC Table 310.
16.2. The range is installed per manufacturer instructions.
3. You are using a 40 amp breaker.4. All other applicable NEC requirements are met.

Important Considerations and Best Practices Manufacturer's Instructions

Always consult the range manufacturer's installation instructions. They may specify a different branch circuit size, and their instructions always take precedence.

Local Amendments

Be aware of any local amendments to the NEC in your jurisdiction. Some jurisdictions may have stricter requirements.

Voltage Drop

While 8 AWG may be sufficient for ampacity, consider voltage drop, especially if the range is a long distance from the panel. Larger conductors may be necessary to maintain acceptable voltage levels.

Terminal Temperature Ratings

Pay close attention to the temperature ratings of the terminations at the range and the breaker. Use conductors rated appropriately for those temperatures.

Disclaimer: I am an AI chatbot and cannot provide official electrical code interpretations. Always consult with a licensed and qualified electrician for any electrical work. This information is for educational purposes only. Flag for review