FREE Journeyman Electrician’s Branch Circuits Questions and Answers
What exactly is a single branch circuit?
A branch circuit classified as an individual branch-circuit exclusively feeds power to one particular piece of equipment. Branch circuits serving electric water heaters, dryers, ranges, cooktops, air conditioners, etc. are examples of individual branch circuits.
If the computation for branch-circuits yields a value of 3.1, how many branch-circuits should be installed?
If your computation is not a whole number while computing branch circuits. 3.1 must then move on to the following whole number, 4, in this instance. In other words, only the entire circuit breaker can be installed.
What is the dwelling unit load per square foot?
Depending on the kind of occupancy, as shown in Table 220.12, lighting loads for particular occupancies shall be based on the unit load per square foot. The table shows that the unit load for residential units is 3 VA per square foot.
The branch circuits delivering 125-volt, single-phase, 15- or 20-ampere outlets in a garage Area in terms of residential occupancies.
The branch circuits delivering 125-volt, single-phase, 15- or 20-ampere outlets in a garage area in terms of residential occupancies shall not supply any other outlets outside of the garage. This requirement helps prevent overloading of circuits and ensures that the garage outlets are dedicated to serving the needs of that specific area without extending to other areas of the dwelling.
The usage of liquid-tight flexible metallic conduit (LFMC) is not permitted.
The usage of liquid-tight flexible metallic conduit (LFMC) is not permitted where subject to physical damage. Liquid-tight flexible metallic conduit is often used to provide protection for conductors in wet or damp environments, but its use might be restricted in areas where it could be easily damaged due to its flexible nature. In areas where physical damage is a concern, more rigid conduit options may be required to ensure the protection and integrity of the wiring.
Find the total area of a five-story building with 125 feet by 100 feet of outside space.
A multi-story building's area is calculated in square feet by multiplying the building's length by its width by the number of stories: 100 feet by 125 feet by five equals 62,500 square feet.
Outside measurements of a swelling unit are 60 feet by 45 feet. How many 120-volt, 15-ampere general lighting brand circuits are need for the house?
The length of the box must not be less than ___times the trade diameter of the largest conduit entering the box when a pull box is to be installed and conductors of size 4 AWG and bigger are to be pulled straight.
The length of the box must not be less than eight times the trade diameter of the largest conduit entering the box when a pull box is to be installed and conductors of size 4 AWG and bigger are to be pulled straight. This requirement helps ensure that there is enough space within the pull box for proper bending and maneuvering of the conductors during installation.
Where the motor controller also serves as a disconnecting means, it shall open all _____ conductors to the motor.
Where the motor controller also serves as a disconnecting means, it shall open all ungrounded conductors to the motor. This ensures that all power sources to the motor are disconnected when the motor controller is operated, enhancing safety during maintenance or emergency situations.
Where flammable liquid-produced vapors or combustible liquid-produced vapors are or may be present in air amounts sufficient to form explosive or ignitable combinations, are those sites classified as class ____ hazardous?
Where flammable liquid-produced vapors or combustible liquid-produced vapors are or may be present in air amounts sufficient to form explosive or ignitable combinations, those sites are classified as Class I hazardous locations. This classification is used to indicate areas where the presence of flammable gases, vapors, or liquids poses a potential explosion or fire hazard, and specific safety measures must be taken to prevent ignition sources and ensure safe operation.
For twenty (20) baseboard heaters, each rated at 2,250 watts at 220-volts, single-phase, how many branch circuits of 40 amps, at 220-volts, are necessary?
We use the following calculation to compute the bare minimum of branch circuits needed to serve fixed electric space heating equipment:
Number of circuits = (Load VA x 125%) / Circuit VA In this case, the number of circuits: (2,250 x 20 x 125%) / (220 x 40) = 6.4
Hence, we need at least 7 circuits.
A minimum ampacity of: must be present in the branch circuit conductors feeding a 6 kW, 240-volt, single-phase water heater.
‥ First, calculate the current I:
I = P/E = (6 kW x 1000) 240 volts = 25 amperes
‥ Then, the branch circuit conductors are required to have an ampacity of at least:
25 x 125% - 31.25 amperes
What is the MAXIMUM continuous load, measured in Volt Ampere, that can be protected by a 20 Ampere Rated Circuit Breaker on a 240 Volt, Single Phase Branch Circuit?
It is a common belief that a branch circuit should never be loaded above 80% of the overcurrent device rating (80% is equal to inverse of 125, per NEC 210,20 (A)). The maximum continuous load is therefore 3,840 VA (240 volts x 20 amperes x 80%).
What is the MAXIMUM flexible chord length allowed for a recirculating pump motor on a swimming pool at a residence?
The maximum flexible cord length allowed for a recirculating pump motor on a swimming pool at a residence is typically 3 feet. This limitation helps ensure that the cord is properly supported and that there is minimal risk of entanglement or damage to the cord in a potentially wet and hazardous environment. Always adhere to local electrical codes and safety guidelines when installing equipment around swimming pools.
When a load is continuous, the maximum current is anticipated to last for AT LEAST:
A load for which the maximum current is anticipated to last for at least three hours.
Determine the MAXIMUM number of 120-volt fluorescent luminaries (lighting fixtures), each requiring 1.6 amperes, that may be supplied from a 120-volt lighting branch circuit with a 20 ampere rating for a retail store.
The NEC 220.18 (B) for Inductive and LED Lighting Loads calculates that a fluorescent luminaire can have a maximum of 10 luminaries.