Technical information

FEEDER AND BRANCH CIRCUITS

suitable as Branch Circuit Protection and as general panel protection) and several

other types of control fuses (adapted to the use of just control circuits:

Supplemental Fuses).

Note that the NEMA standards are construction standards: the fuses are, in terms

of sizes and dimensions, identical

regardless of the manufacture (as it happens in

Europe). Fuse holders are made especially for some types of fuses as indicated in

the approval markings of the certifying NRTL laboratory.

North American fuses differ from the European types and cannot be

interchanged. Furthermore they do not correspond with any EN

harmonized standard rule.

A list of the main types of fuse identified by the Underwriters Laboratory is given:

In the USA the NFPA 79 standard for Industrial Machinery (and the relative

UL508A section) recommends the use of CC, J, RK-1, RK - 5 fuses (already

highlighted). It is recommended that the design be unified through the

adoption of these types in the electrical equipment.

Furthermore UL508A prohibits the use of H, H (renewable), K, G and T fuses in

the Industrial Machinery: it is an additional UL provision.

Fuse type UL standard Definition Adjusted for Control

power circuits

C248 – 2Class C Fuses xx

CA, CB 248 – 3Class CA and CB Fuses xx

CC 248 – 4Class CC Fuses xx

G248 – 5Class G Fuses xx

H248 – 6Class H Fuses (Non Renewable) xx

H (Renewable) 248 – 7Class H Fuses Renewable xx

J248 – 8Class J Fuses xx

K248 – 9Class K Fuses xx

L248 – 10 Class L Fuses xx

Plug fuses 248 – 11 Plug Fuses xx

R (RK-1, RK-5) 248 – 12 Class R Fuses xx

Special Purpose 248 – 13 Special Purpose xx

Supplemental Fuses 248 – 14 Supplemental Fuses xx

T248 – 15 Class T Fuses xx

[a] the semi-conductor type Special Purpose fuses can be used as protection in power circuits (BCP) only if

explicitly required in the label or in the instructions of the component to be protected.