Branch Circuit Calculations Flashcards
7 cards from real Licensed Electrical Contractor practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Branch Circuit Calculations flashcards as text
A 20-ampere branch circuit serves a small appliance circuit in a kitchen. What is the maximum load, in watts, allowed on this circuit at 120V using the 80% rule?
Answer: 1,920 watts
The 80% continuous load rule limits a 20A circuit at 120V to 20A × 0.80 × 120V = 1,920 watts.
Per NEC Article 210, how many small appliance branch circuits are required for the kitchen countertop receptacle outlets in a dwelling unit?
Answer: At least two 20-ampere circuits
NEC 210.11(C)(1) requires at least two 20-ampere small appliance branch circuits for kitchen countertop receptacles.
A branch circuit conductor must be sized so that voltage drop does not exceed what percentage for branch circuits per NEC recommendations?
Answer: 3%
The NEC recommends (informational note) that voltage drop on a branch circuit not exceed 3% for best performance.
What is the minimum wire gauge (AWG) required for a 20-ampere, 120V branch circuit using copper conductors?
Answer: 12 AWG
NEC 240.4(D) requires 12 AWG copper conductors for circuits protected by 20-ampere overcurrent devices.
A branch circuit supplies a 7.5 kVA, 240V single-phase motor load. What is the full-load current of this motor?
Answer: 31.25 amperes
I = kVA × 1000 / V = 7,500 / 240 = 31.25 amperes for a single-phase load.
What NEC section governs the maximum number of outlets permitted on a branch circuit in a commercial occupancy?
Answer: There is no NEC limit on number of outlets; load calculations govern
The NEC does not set a maximum number of outlets per branch circuit; the total connected load determines the circuit size.
For a branch circuit supplying a continuous load, the overcurrent protective device must be rated at no less than what percentage of the continuous load?
Answer: 125%
NEC 210.20(A) requires the overcurrent device to be rated at not less than 125% of the continuous load.