Module 10 - Circuit Breakers & Fuses
What are the circuit breaker ampere groupings and why is this important?
Circuit breakers are classified into ampere groupings that match specific physical dimensions. These numbers, commonly referred to as the frame size, which are terms applied to groups of molded-case circuit breakers that re physiclaly interchangeable according to given current ranges. Each group is classified by the largest ampere rating of its range. 15A-100A 125A-225A 250A-400A 500A-1,000A 1,200A-2,000A
What are the two types of overload devices normally used in electrical work?
Fuse and Circuit Breaker
Where is the current rating of a circuit breaker located?
Located on the handle of the breaker
What are the two tests that circuit breakers are subjected to and to what ampere max?
NEMA (does not list devices) - Self Certification Test UL (does list devices) - Unbiased Witnesses: UL tests have been limited to a maximum of 10,000A in the past, so the emphasis was placed on the NEMA tests with higher ratings.
Explain NEC 240.1
See Codebook
Explain NEC 240.2
See Codebook
Explain NEC 240.83(C)&(E)
See Codebook
Explain NEC 240.85
See Codebook
NEC section 240.60(C) states what for fuses for branch or feeder circuits?
See Codebook
When would it be best to use single element fuses?
Single-element fuses have a very high speed of response to overcurrents. They provide excellent short circuit component protection. They are best used in circuits that are not subject to heavy transient surge currents and the temporary overload of circuits with inductive loads such as motors, transformers, and solenoids.
Define the following circuit breakers including interrupting rating? -Standard interrupting capacity circuit breaker: -High interrupting capacity circuit breaker: -Current limiting circuit breaker:
Standard Interrupting capacity circuit breaker: SIC circuit breakers can be identified by their black operating handles and black printed interrupting rating labels, Has an interrupting rating of 10,000A High Interrupting capacity circuit breaker: HIC circuit breakers are used if a circuit breaker requires higher interrupting capacity than the standard ratings, Has an interrupting rating of 65,000A Current limiting circuit breaker: Operates extremely fast to provide downstream protection for other types of overcurrent devices. Has an interrupting rating of 100,000A
Who are the two certifying agencies for circuit breakers?
Underwriters Laboratory (UL) and Canadian Standards Association (CSA)
When sizing fuses what can be of great value?
a schematic drawing
What is coordination as it pertains to overcurrent devices?
coordination is the name given to the time-current relationship among a number of over-current devices connected in series, such as fuses in a main feeder, sub-feeder, and branch circuits.
