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Codeology 3

Codeology Lesson 3 Overcurrent Device Ratings

QuestionAnswer
If a conductor’s ampacity does not correspond to a standard circuit breaker or fuse ampere rating found in _1_, __2__ permits selecting the next standard ampere rating if specific conditions in __3___ are met. 1) 240.6 2)240.4(B) 3) 240.4(B)
Which of the following is not a rating used when selecting overcurrent protective devices? a. Ampere rating Incorrect b. FRAME SIZE c. Interrupting rating Incorrect d. Voltage rating Incorrect
The voltage of an electrical system must be equal to or greater than voltage rating of an OCPD. False
Ampere rating, voltage rating, interrupting rating where other than 10,000 amperes, current limiting where applicable, and the name or trademark of the manufacturer are all items which must be plainly marked on the barrel of a fuse. True The corzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzrect answer is: 240.60(C)
A fuse or circuit breaker with a 600-volt AC rating is permitted to be used on 300-volt DC application by the half voltage rule in NEC Article 240. False Note: for DC applications, a fuse or circuit breaker should be marked with a DC voltage rating equal or greater than the system DC voltage.
Fuses have straight and slash voltage ratings. False Note: By their design, fuses are full voltage rated devices. Slash voltage ratings are not an issue. For example, Class J fuses are rated at 600 V AC and are utilized on systems rated 600 V AC on any distribution system.
All circuit breaker are required to have their ampere ratings marked on the circuit breaker handle or escutcheon False Note: See 240.83(B) and 240.83(A).
Service equipment in commercial installations is required to be field marked with the maximum available fault current and date of fault calculations. True The correct answer is: 110.24(A)
Straight voltage rated circuit breakers of the proper voltage rating (the volt rating is greater than system line-line voltage) are allowed to be used on which of the following voltage systems? I. 120 V 1 Ø, 2 W, solidly grounded II. 120/240 V 1 Ø, 3 W, solidly grounded III. 208 Y/120 V 3 Ø, 4 W, solidly grounded IV. 240 V 3 Ø, 3 W, ungrounded or corner grounded delta V. 480 Y/277 V 3 Ø, 4 W, solidly grounded VI. 480 V 3 Ø, 3 W, ungrounde
Slash voltage rated circuit breakers of the proper voltage rating are allowed to be used on which of the following voltage systems? I. 120 V 1 Ø, 2 W, solidly grounded II. 120/240 V 1 Ø, 3 W, solidly grounded III. 208 Y/120 V 3 Ø, 4 W, solidly grounded IV. 240 V 3 Ø, 3 W, ungrounded or corner grounded delta V. 347 V VI. 480 Y/277 V 3 Ø, 4 W, solidly grounded VII. 480 V 3 Ø, 3 W,
When a fuse or circuit breaker interrupts a short-circuit current exceeding its interrupting rating, the UL product standards require that an indication pin on the fuse or circuit breaker actuate so that the Electrical Worker knows to replace the device w false Review the still photos from Figure 11 and the associated videos available.
Generally, conductors shall be protected at their ampacities by branch-circuit overcurrent devices True 240.4 there can be other requirements and permissions. See 240.4(A) through (G)
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 10 AWG Aluminum → 25 amperes, 12 AWG Aluminum → 15 amperes, 10 AWG Copper → 30 amperes, 12 AWG Copper → 20 amperes, 16 AWG Copper → 10 amperes, 18 AWG Copper → 7 amperes
The highest current at rated voltage that a device is identified to interrupt under standard test conditions describes ? . b. interrupting rating NEC Reference 100
Fuses and circuit breakers which are intended to interrupt current at fault levels must have an interrupting rating at applied voltage sufficient for the available short circuit at its line terminals. True
Per the second paragraph of 110.9, devices such as motor starters and switches must have interrupting ratings at applied voltage sufficient for the available short circuit at its line terminals. False
If a branch-circuit fuse is not marked with an interrupting rating, then the interrupting rating for that fuse is ? . 10,000A NEC Ref: 240.6
If a branch-circuit circuit breaker is not marked with an interrupting rating, then the interrupting rating for that circuit breaker is ? . 5,000 240.83(c)
Interrupting ratings are required to be marked on supplemental protective devices False NEC ref: 240.60(C)
Typically what is the single most influencing factor on the magnitude of the available short-circuit current at the service? Transformer supplying the service
New service equipment in commercial buildings must be field marked with the maximum available fault current and the date the calculations were performed. True
New service equipment in commercial buildings must be field marked with the maximum available fault current and the date the calculations were performed. True
A panelboard that is located downstream from a service disconnect is calculated to have 45,000 amperes of available fault current. A circuit breaker installed in this downstream panel must have an interrupting rating equal or greater than ? . 45,000 A Correct Lesson 3 introduces interrupting rating. This question assumes using fully rated circuit breakers. Series rating is covered later. If the circuit breaker in the downstream panelboard were part of a series rating of at least 45 kA, then t
What is/are the most common interrupting ratings for current-limiting fuses? 200,000 A and 300,000 A
Created by: Shawnt321
 

 



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