IEC Overcurrent Protection 5

Question 1

Per NEC 240.60, cartridge fuses and fuseholders for 250V shall NOT be used on systems where the nominal voltage between any two conductors exceeds:

Accepted Answer

250V

Answer

Cartridge fuses rated 250V are limited to circuits where the voltage between any two conductors does not exceed 250V.

Question 2

Which overcurrent device characteristic describes the ability to interrupt a fault current without damage to itself?

Accepted Answer

Interrupting rating

Answer

The interrupting rating specifies the maximum fault current an overcurrent device can safely clear without being destroyed.

Question 3

Per NEC 240.33, enclosures for overcurrent devices must be mounted in a:

Accepted Answer

Vertical position as close as practical

Answer

NEC 240.33 requires overcurrent device enclosures to be mounted vertically unless this is shown to be impracticable.

Question 4

A Type S fuse adapter is inserted into an Edison-base fuseholder to accept which type of fuse?

Accepted Answer

Type S plug fuse

Answer

Type S adapters accept only Type S fuses of the matching ampere rating, preventing installation of an oversized fuse.

Question 5

Per NEC 240.21(C), transformer secondary conductors are not required to have overcurrent protection at the secondary terminals if the primary overcurrent device rating does not exceed the value calculated using which multiplier for a 2-wire secondary?

Accepted Answer

167%

Answer

For a 2-wire transformer secondary, the primary OCPD may be up to 167% of the primary FLC as a substitute for secondary protection per NEC 240.21(C)(1).

IEC - Independent Electrical Contractors Practice Test

IEC - Independent Electrical Contractors Practice Test

IEC Overcurrent Protection 5