If the branch-circuit protective device value determined by NEC does not match a standard ampere rating, what is permitted?

If the branch-circuit protective device value determined by NEC does not match a standard ampere rating, what is permitted?

• A. Use a lower rating
• B. Use the next higher standard rating
• C. Use a higher rating not exceeding the next higher standard rating
• D. Use any rating that is convenient

Answer: (C)

When sizing branch-circuit protection, you must use a standard device rating. If the calculated value doesn’t match a standard ampere rating, you upsize to the next available standard size, but you cannot go beyond the next higher standard rating. In other words, choose a rating that is at least as large as the calculated load and no larger than the next standard rating. This ensures the protection is sufficient without selecting an unnecessarily large device. For example, if the calculation comes to 13 A, use the 15 A standard size; if it comes to 18 A, use the 20 A standard size. You wouldn’t jump to 25 A because that would exceed the next higher standard rating.

When sizing branch-circuit protection, you must use a standard device rating. If the calculated value doesn’t match a standard ampere rating, you upsize to the next available standard size, but you cannot go beyond the next higher standard rating. In other words, choose a rating that is at least as large as the calculated load and no larger than the next standard rating. This ensures the protection is sufficient without selecting an unnecessarily large device. For example, if the calculation comes to 13 A, use the 15 A standard size; if it comes to 18 A, use the 20 A standard size. You wouldn’t jump to 25 A because that would exceed the next higher standard rating.