TN LLE Fault Current and OCPD Ratings 2

Question 1

What does AIC stand for on a circuit breaker nameplate?

Accepted Answer

Ampere Interrupting Capacity

Answer

Alternating Inrush Current

Answer

Automatic Isolation Control

Answer

Ampere Input Circuit

Question 2

Per NEC 110.9, what must the interrupting rating of equipment be sufficient to handle?

Accepted Answer

The available fault current at the line terminals

Answer

The normal operating current

Answer

Twice the circuit breaker rating

Answer

The locked-rotor current of the largest motor

Question 3

What is the typical available fault current at a residential 200A service panel?

Accepted Answer

10,000-22,000 amperes

Answer

200 amperes

Answer

1,000-5,000 amperes

Answer

100,000+ amperes

Question 4

What is the purpose of a current-limiting fuse?

Accepted Answer

To limit the peak let-through current to a value less than the available fault current

Answer

To reduce the electric bill

Answer

To prevent voltage spikes

Answer

To reduce starting current on motors

Question 5

What happens if a circuit breaker with a 10,000 AIC rating is installed where the available fault current is 25,000 amperes?

Accepted Answer

The breaker may fail to interrupt the fault, potentially causing explosion, fire, or arc flash

Answer

The breaker will trip faster than normal

Answer

Nothing — breakers automatically adjust

Answer

The breaker will simply not trip

Question 6

Per NEC 110.24, what marking is required on service equipment regarding fault current?

Accepted Answer

The maximum available fault current and date of calculation must be marked

Answer

No marking is required

Answer

Only the breaker AIC rating needs to be visible

Answer

A warning label about shock hazard only