Which value is used to determine the minimum circuit ampacity for the unit as listed on the nameplate?

Which value is used to determine the minimum circuit ampacity for the unit as listed on the nameplate?

• A. 32 A
• B. 1.7 A
• C. 37.9 A
• D. 60 A

Answer: (C)

The main idea here is how to size the conductors feeding a motor or unit. The minimum circuit ampacity (MCA) is the current the branch conductors must be able to carry, and it’s derived from the nameplate’s full-load current (FLC) by multiplying that FLC by 1.25. This provides a safety margin for startup and continuous operation. So, you take the full-load current listed on the nameplate and apply the 1.25 factor to get the MCA. In this case, that calculation gives 37.9 A, which is the MCA used for sizing the wiring and overcurrent protection. The other numbers reflect either the FLC or other currents not used for determining MCA, so they aren’t the value used for the MCA.

The main idea here is how to size the conductors feeding a motor or unit. The minimum circuit ampacity (MCA) is the current the branch conductors must be able to carry, and it’s derived from the nameplate’s full-load current (FLC) by multiplying that FLC by 1.25. This provides a safety margin for startup and continuous operation.

So, you take the full-load current listed on the nameplate and apply the 1.25 factor to get the MCA. In this case, that calculation gives 37.9 A, which is the MCA used for sizing the wiring and overcurrent protection. The other numbers reflect either the FLC or other currents not used for determining MCA, so they aren’t the value used for the MCA.