Mike Holt - 3rd Year 2020 NEC Quarter 4 Exam prep
In order to properly size overcurrent protection for a control circuit, it's necessary to distinguish whether the control circuit is a _____.
common (tapped) control circuit or a separate control circuit keyboard_backspace correctkeyboard_backspace selected
The circuit conductors between the final overcurrent device and the outlet or equipment is a ______.
common control circuit
An electromechanical device used for repeatedly establishing and interrupting an electric power circuit is a ______.
contactor
The circuit of a control apparatus or system that carries the electric signals directing the performance of the controller but doesn't carry the main power current is called a ______.
control circuit
A device used to supply reduced voltage to a control circuit is called a _____.
control circuit transformer
Where a dual-voltage control transformer is used, and the control circuit is 120V on the secondary, the _____.
dual primary windings are connected in series if 480V
In a(n) _____ contactor, when the coil is energized, the power contacts close. When the coil is de-energized, the power contacts open.
electrically held
In thermostat conductor termination, the color green is typically used for the _____.
fan
Many types of overload protectors operate on the relationship between _____.
heat and current
A very common type of overload device is a eutectic alloy thermal overload. This type of overload device is sometimes called a _____.
heater
Ladder diagrams are also known as _____.
line or elementary diagrams
The terms "T1," "T2," and "T3" refer to the terminals on the _____.
load side of a motor starter
A _____ contactor has two coils and maintained-contact power contacts, and is similar to a simple toggle switch in that it's On in one position, and Off in the other position.
mechanically held
A _____ is any switch or device that's normally used to start and stop a motor by making-and-breaking the motor-circuit current.
motor controller
If a toggle switch for a motor is closed and the power goes out, the _____.
motor will start when the power comes back on
The NEC typically requires _____ overload relay unit(s) for every ungrounded conductor.
one
A(An) _____ limit switch is sometimes used when the detection of very small objects is required.
optical
Pressing either the forward PB or the reverse PB to reverse direction while the motor is already running causes stress in the motor, and briefly causes a high current which produces abnormal heating in the motor. This is called a(n) _____.
plugging reversal
In thermostat conductor termination, the color red is typically used for the _____.
power from the transformer
A device operated by a change in one electrical circuit to control a device in the same circuit or another circuit is a ______.
relay
When the selector switch of a forward-reverse control circuit is in the _____ position, the forward portion of the circuit is disconnected.
reverse
Overload current _____.
rises slowly and has a long duration
A manually operated switch that uses a rotating motion for actuating a device is called a ______.
selector switch
A circuit in which all the components or contact symbols are connected end-to-end (as in a continuous loop), providing only one path for current flow is called a ______.
series circuit
A wye configuration for a three-phase motor is also called a _____-configured or connected motor.
star
A motor control circuit, for the most part, is simply a _____ and a motor.
switch
Heating the sensing bulb of a _____ switch, increases the pressure in the bulb, which in turn activates the contacts inside the switch housing.
temperature
According to the NEC, a common (tapped) control circuit can be protected by _____.
the branch-circuit or supplemental overcurrent protection device supplying the moto
In a dual-voltage, three-phase motor, the VA of the motor if connected for the lower voltage is _____.
the same as that of the higher voltage
A standard on-off wall-mounted snap switch used for most lighting outlets is an example of a _____.
toggle switch
Selector switches use _____ to show the position of switch contacts in relation to the switch position.
truth or target tables
When connected at the lower voltage, a dual-voltage, three-phase motor draws _____ than when connected at the higher voltage.
twice as much current
Residential type doorbell circuits are typically _____.
16V
Automatic controls that can be used in a simple motor control arrangement include_____.
Answer 1: pressure switches Answer 2: temperature switches Answer 3: time clocks Answer 4: all of these
A typical installation that might use a flow switch is _____.
Answer 1: to detect air flow in a duct Answer 2: a fire sprinkler system Answer 3: an irrigation system Answer 4: all of these
Pressure switches can monitor the pressure of _____.
Answer 1: water and oil Answer 2: gases and vapors Answer 3: air Answer 4: all of these
The point at which an electrical component is connected to another electrical component is called ______.
a terminal
Which of the following can be considered a motor controller?
all of these
Which of the following can be considered control devices rather than motor controllers?
all of these
Limit switches have various types of actuating methods, and different applications, but the basic operation for all limit switches is the same.
TRUE
Most pushbutton switches are the momentary contact type.
TRUE
A 2-wire control circuit doesn't have low-voltage protection.
True
A 3-wire control circuit has built-in low-voltage protection.
True
A common control circuit shouldn't be used when the branch circuit for the motor is 480V unless extreme caution is exercised.
True
A control transformer typically reduces the voltage from L1 and L2 for the control circuit, such as reducing a 480V branch circuit for the motor to 120V for the control circuit.
True
A remote-control circuit is any electric circuit that controls any other circuit through a relay or equivalent device.
True
A wye/delta-connected motor is commonly used where reduced inrush current or reduced starting torque is needed.
True
All of the windings of three-phase motors are always wired together to produce three distinct windings called Phases.
True
Connection diagrams are also called wiring diagrams.
True
Contactors don't provide overload protection.
True
For a Class 1 control circuit used as a separate control circuit, control conductors 14 AWG and larger are protected at their ampacity.
True
Iluminated doorbell pushbuttons can be wired in the same way as doorbell pushbuttons that aren't illuminated.
True
In a basic 3-wire control circuit, the stop PB is in series with the coil, and the start PB is in parallel with the NO auxiliary contacts.
True
In a magnetic motor starter, when the coil is energized, a normally open (NO) set of contacts will close, and a set of normally closed (NC) contacts will open.
True
In many cases, equipment for control and signaling comes with the manufacturer's instructions.
True
In some cases, a general-use snap switch can be used as a disconnecting means for a motor rated 2 hp or less.
True
In the field, most ladder and wiring diagrams don't use numbers such as F1, F2, R1, or R3 for the auxiliary contacts.
True
Most three-phase motors are used in commercial and industrial applications.
True
Overcurrent protection is always required on the primary side of a control transformer, unless it will create a hazard such as for the control circuit for a fire pump motor.
True
Reversing any two lines (power-supply conductors) to a three-phase motor causes the motor to run in the other direction.
True
Schematics show motors and control equipment in their "resting" or "shelf" state.
True
Sequence control is the method by which the control circuits of magnetic starters are interconnected so that one must be started before the second one is energized.
True
Short-circuit or ground-fault current is many times higher than running current and must open the protection device as quickly as possible to minimize the damage.
True
Solenoid valves can be used with gases or liquids.
True
The most common types of motors used for single-phase reversing are capacitor-start motors and split-phase motors.
True
There's no standard color code for the use of pilot (indicator) lights.
True
16 AWG control conductors that extend beyond the motor control equipment enclosure must be protected with a protection device rated no more than _____.
10A
_____ AWG control conductors located within the equipment enclosure are protected by the branch-circuit overcurrent device if it's rated 40A or less.
16
A separate control circuit is _____.
Answer 1: not taken from the branch circuit feeding the motor Answer 2: typically a Class 1 control circuit Answer 3: must conform to Article 725 of the NEC Answer 4: all of these
Generally, conductors smaller than _____ AWG are only used by manufacturers for the internal wiring of equipment.
14
According to the NEC, control circuit conductors can be as small as _____ AWG.
18
For motor control applications, the relay coil voltages are typically rated between _____.
24V and 600V
Whenever a control circuit makes use of holding contacts that drop out on power loss, it's called a "_____" circuit regardless of the actual number of conductors necessary to provide for all circuit options.
3-wire
A general-use ac snap switch can be used as a motor disconnect or controller for stationary motors rated 2 hp or less and _____ or less providing the requirements of 430.83(C) or 430.109(C)(2) of the NEC are met.
300V
Overcurrent may result from _____.
Answer 1: overload Answer 2: short circuit Answer 3: ground fault Answer 4: any of these
Overload relays have 10-second, 20-second, or 30-second ratings. These ratings are the maximum seconds an OL takes to trip at _____ percent of its current rating.
600
Which of the following item(s) can be considered a manual control switch?
Answer 1: A toggle switch. Answer 2: A safety switch. Answer 3: A drum switch. Answer 4: all of these
_____ are devices using coils that can be used to facilitate remote-control functions.
Answer 1: Contactors Answer 2: Magnetic starters Answer 3: Solenoids Answer 4: all of these
_____ lamps are commonly used in pilot lights.
Answer 1: Incandescent Answer 2: Neon Answer 3: LED Answer 4: any of these
Some common contact terminology abreviations used with time-delay relays includes:
Answer 1: NOTC Answer 2: NCTO Answer 3: NOTO and NCTC Answer 4: all of these
Some chimes _____.
Answer 1: are electronic Answer 2: can play music Answer 3: go ding-dong Answer 4: all of these
A basic 2-wire control circuit goes from a power supply, which is L1 if from the contactor (common control wiring), to a 2-wire control device such as a _____.
Answer 1: float switch Answer 2: pressure switch Answer 3: temperature switch Answer 4: any of these
It's possible for a motor to become so hot that it will burn out or start a fire. A common cause of overload is _____.
Answer 1: low voltage to the motor Answer 2: a locked rotor Answer 3: single-phasing (one line of a three-phase circuit fails) Answer 4: all of these
A separate control circuit is typically a _____ nonpower-limited control circuit and must comply with the requirements of Article 725, Part II of the NEC.
Class 1
A _____ overload relay is typically used with hermetic motors, and motors with short locked-rotor time capacity.
Class 10
A 240V toggle switch is an example of a _____ switch.
DPST
A capacitive proximity switch might be suitable for metal objects. An inductive proximity switch is used with nonmetallic or plastic objects.
FALSE
A float switch, also called an "over-flow switch," is generally used to start and stop a pump motor in order to control the level of water or other liquid.
FALSE
The most uncommon timing relays used today are solid-state (electronic) timers as well as timers incorporated into solid-state control equipment and PLC's.
FALSE
Timing relays with instantaneous contacts operate with a minimal amount of time delay.
FALSE
According to the NEC, a common (tapped) control circuit is considered a branch circuit.
False
Drum switches provide motor overload (OL) protection.
False
Switching devices such as float switches, limit switches, or relays always come with only one set of contacts.
False
With common control wiring, the power source for the control circuit is separate from the power circuit wiring.
False
When wiring a control transformer for a 3-wire control circuit, the higher-voltage terminals typically have a letter _____ with the terminal numbers.
H
_____ are used to represent the function of the control circuit and the associated devices, but don't show the components of the control circuit in their actual positions.
Ladder diagrams
_____ means that if power goes off to the control circuit, the equipment won't automatically restart when power is restored.
Low-voltage protection
A common abbreviation for a safety switch is _____.
SSW
