26401 Load and Feeder Calculations
Questions and Answers | Latest Version
| 2024/2025 | Correct & Verified
What is the purpose of load calculations in electrical systems?
✔✔ To determine the total electrical demand of a system.
Why is it important to size conductors correctly in a feeder system?
✔✔ To prevent overheating and ensure safe operation.
What is the standard voltage drop percentage allowed for feeder circuits?
✔✔ 3%.
What should be included in the calculation of a feeder load?
✔✔ The total connected load, including continuous and non-continuous loads.
What is the definition of a continuous load?
✔✔ A load that runs for three hours or more.
1
,Why must continuous loads be calculated at 125% in feeder sizing?
✔✔ To account for sustained demand and ensure safety margins.
What is the main purpose of overcurrent protection devices in a feeder circuit?
✔✔ To protect conductors from excessive current.
What is the formula to calculate voltage drop in a feeder circuit?
✔✔ Voltage Drop = (2 × Length × Current × Resistance) ÷ 1000.
Why are demand factors applied in feeder calculations?
✔✔ To account for the likelihood that not all loads will operate simultaneously.
What is the ampacity of a conductor?
✔✔ The maximum amount of current a conductor can safely carry.
Why is it necessary to derate conductors in high-temperature environments?
✔✔ To prevent insulation damage and overheating.
2
, What is the role of a feeder in an electrical distribution system?
✔✔ To carry power from the service equipment to branch circuits or subpanels.
What information is needed to size feeders properly?
✔✔ Total load, demand factors, and voltage drop considerations.
Why are neutral conductors sometimes sized smaller than phase conductors in feeder
calculations?
✔✔ Because the neutral typically carries less current in balanced loads.
What is a branch circuit?
✔✔ A circuit that originates from a feeder and supplies power to specific devices or equipment.
What is the purpose of calculating the short-circuit current in a feeder?
✔✔ To ensure the overcurrent protection device can handle fault conditions.
What does the National Electrical Code (NEC) require when sizing feeders for motors?
✔✔ To use 125% of the motor’s full-load current.
3
Questions and Answers | Latest Version
| 2024/2025 | Correct & Verified
What is the purpose of load calculations in electrical systems?
✔✔ To determine the total electrical demand of a system.
Why is it important to size conductors correctly in a feeder system?
✔✔ To prevent overheating and ensure safe operation.
What is the standard voltage drop percentage allowed for feeder circuits?
✔✔ 3%.
What should be included in the calculation of a feeder load?
✔✔ The total connected load, including continuous and non-continuous loads.
What is the definition of a continuous load?
✔✔ A load that runs for three hours or more.
1
,Why must continuous loads be calculated at 125% in feeder sizing?
✔✔ To account for sustained demand and ensure safety margins.
What is the main purpose of overcurrent protection devices in a feeder circuit?
✔✔ To protect conductors from excessive current.
What is the formula to calculate voltage drop in a feeder circuit?
✔✔ Voltage Drop = (2 × Length × Current × Resistance) ÷ 1000.
Why are demand factors applied in feeder calculations?
✔✔ To account for the likelihood that not all loads will operate simultaneously.
What is the ampacity of a conductor?
✔✔ The maximum amount of current a conductor can safely carry.
Why is it necessary to derate conductors in high-temperature environments?
✔✔ To prevent insulation damage and overheating.
2
, What is the role of a feeder in an electrical distribution system?
✔✔ To carry power from the service equipment to branch circuits or subpanels.
What information is needed to size feeders properly?
✔✔ Total load, demand factors, and voltage drop considerations.
Why are neutral conductors sometimes sized smaller than phase conductors in feeder
calculations?
✔✔ Because the neutral typically carries less current in balanced loads.
What is a branch circuit?
✔✔ A circuit that originates from a feeder and supplies power to specific devices or equipment.
What is the purpose of calculating the short-circuit current in a feeder?
✔✔ To ensure the overcurrent protection device can handle fault conditions.
What does the National Electrical Code (NEC) require when sizing feeders for motors?
✔✔ To use 125% of the motor’s full-load current.
3
