NATE Core Exam 152: Electrical Theory and Practices Study Guide, Exams of Physics

Download NATE Core Exam 152: Electrical Theory and Practices Study Guide and more Exams Physics in PDF only on Docsity! NATE core Exam 152 Exam Questions with 100% Correct Answers What are the five basic components to any schematic? - ✅✅✅1. A power supply 2. A path for the power 3. A load or component that operates from the power. 4. A switch or component that interrupts the power to the load. 5. A legend or key that explains what the various symbols and abbreviations used in the schematic mean. What are the three basic types of wiring diagrams used in the HVACR trade? - ✅✅✅1. The ladder diagram 2. The pictorial diagram 3. The installation diagram Describe the characteristics of a ladder diagram - ✅✅✅1. Provides the most helpful information for electrical troubleshooting 2.The intention of the overall schematic is to show how the circuit functions not how it actually looks. Page 1 of 26 Describe the characteristics of a pictorial diagram - ✅✅✅1. Usually includes drawings that more closely resemble the components themselves rather than the symbols. 2. Provides the best indication of the actual positions of the components in the equipment or control panel. Describe the characteristics of an installation diagram - ✅✅✅1. Used primarily By the person installing equipment 2. It normally only shows what the terminal board connections are and may or may not include any internal wiring of the unit 3. Field wiring Generally represented as Dashed lines. 4. Thicker lines represent line voltage wiring(120/240 V) 5. Thin lines represent low-voltage control wiring What is a switch? - ✅✅✅A switch is a device that interrupts power to the load. It may be manually or automatically activated by pressure, temperature or it may be an electrically controlled switch What is a load? - ✅✅✅A load is a device that consumes power and converts it into some other form of energy Page 2 of 26 ✅✅✅An honest person is fair and their dealings with other people A condition that must be met to make an agreement legally binding is? - ✅✅✅The agreement must include one promise in exchange for another Which of the following expresses the difference between a feature in a benefit? - ✅✅✅A feature is a special characteristic of a product and a benefit is the value of the customer receives from using the future According to the health and safety regulations, when climbing up or down a ladder the worker must? - ✅✅✅Always face the ladder Refrigerant vapors in large quantities should not be inhaled since they are? - ✅✅✅May cause heart irregularities or fainting Care should be taken before sawing basement walls that are part of the original structural construction of a home because these walls are typically? - ✅✅✅Load bearing Page 5 of 26 Describe a wet bulb thermometer: - ✅✅✅The class thermometer with a wet piece of gauze on the end The federal agency with jurisdiction over the shipping and labeling of refrigerant is? - ✅✅✅DOT The temperature most often used by customers when discussing human comfort is? - ✅✅✅Dry bulb temperature Why are humidifiers used with furnaces? - ✅✅✅Increased relative humidity and make the customer more comfortable The damper used with a bypass humidifier must be? - ✅✅✅Open in the winter The primary purpose for bringing in outdoor air into a residential air distribution system is to? - ✅✅✅Equalize pressure between inside and outside of the structure Why is sound a consideration in locating a heating furnace? - ✅✅✅Excessive noise is annoying to the customer Page 6 of 26 Combustion is what type of process? - ✅✅✅Chemical Any pressure measured by liquid or gas on a surface is typically measured how? - ✅✅✅A reading relative to atmospheric pressure A conductor moving through a magnetic field will? - ✅✅✅Current in the wire The unit of electrical pressure is the? - ✅✅✅Volts Power is measured in? - ✅✅✅Watts (W) Electrical current is measured in? - ✅✅✅amperes (amps) What is ohms law? - ✅✅✅•Voltage (E) = Current aka amps (I) x Resistance (R) • I = E/R • R = E/I Page 7 of 26 Motors above 5 hp that are used with belt driven fans are typically? - ✅✅✅240/460 3 O How was the crank case heater energized? - ✅✅✅It is only on if the compressor contactor is De-energized What is the purpose of an RC component? - ✅✅✅It is a dual capacitor used for the compressor and fan motors In most field wiring diagrams, the color coding of wiring remains consistent. Which of the following is applicable? - ✅✅✅Color coding is almost always used for low-voltage wiring Pictorial wiring diagrams typically show components__ - ✅✅✅In their approximate positions in the equipment A ladder diagram is useful for? - ✅✅✅Troubleshooting a unit An analog VOM meter is an electrical meter that__ - ✅✅✅Displays volts, ohms, or milliamperes on an analog scale Page 10 of 26 A digital multi meter marked "auto-ranging" Will automatically set itself for__ - ✅✅✅Reading take and range of values for all volts, amps or ohms *Using an attached diagram what purpose does PI/S I serve? - ✅✅✅It is a multi pin connector How should a technician measure resistance with a digital ohmmeter? - ✅✅✅Disconnect power, electrically isolate the load, and connect the leads across the load Which meter setting should a technician used to determine whether or not a set of contacts are open in an energize circuit? - ✅✅✅Volts Why would you want to introduce fresh air into an occupied residential structure? - ✅✅✅To create a neutral pressure within the building A ducted distribution system that is not in the Conditioned space and is well sealed on the supply side but has numerous leaks on the return side can create? - ✅✅✅A positive pressure within the condition space Page 11 of 26 What are some of the drivers that can create a negative pressure in a building? - ✅✅✅Chimneys and exhaust fans, the duct system, and a central vacuum system For combustion to occur what three elements are necessary? - ✅✅✅Oxygen, fuel and heat The process of combustion is? - ✅✅✅A chemical reaction Why are humidifiers commonly used along with furnaces and heat pumps during the heating season? - ✅✅✅To improve comfort within the occupied space by increasing the moisture content of the air Which has the greater capacity to hold moisture? - ✅✅✅Hot air The greater difference in temperature between wet bulb and dry bulb__ - ✅✅✅The lower the % RH Dry bulb temperature__ - ✅✅✅•Can be read off of a common thermometer Page 12 of 26 How is current flow measured in an electrical circuit? - ✅✅✅With an ammeter A milliampere is? - ✅✅✅1/1000 of an ampere What happens when current flows through a conductor? - ✅✅✅A magnetic field will be established around that conductor If the conductor is moved through a field of magnetic flux__ - ✅✅✅A Current will be induced in that conductor In an induction transformer, the winding that receives the source voltage is called the? - ✅✅✅Primary winding If the primary voltage on a step down transformer is 110 V and there is a 5:1 turns ratio, what is the secondary voltage? - ✅✅✅22 V *Solution: 110/5 = 22 volts Page 15 of 26 Give them a domestic hot water heater with 4500/4500 watt elements and non-simultaneous operation. What is the anticipated amp draw on an energized element one 220 V is red at that element? - ✅✅✅20.45 Amps *Solution: I E I = P/E 4500/220 = 20.45 amps Given a 1/2 horsepower blower motor that draws 6 A and 118 V during operation. A white meter is then connected and shows a reading of 638 W. What is the power factor for this circuit? (PF = wattmeter reading v x a reading) - ✅✅✅.90 * Solution: 6 x 118 = 708 638/708 = .09 PF = 638 watts = .90 A diode is a electronic circuit that? - ✅✅✅Acts as a conductor in one direction and is an insulator in the other direction Page 16 of 26 What happens to the voltage in a series circuit? - ✅✅✅It divides across each of the loads What happens to the current in a series circuit? - ✅✅✅It is the same at any point in the circuit What happens to the current in a parallel circuit? - ✅✅✅It divides across each of the loads What happens to the voltage in a parallel circuit? - ✅✅✅It is the same at any point in the circuit What should the voltage readings be a crossed a good set of closed contacts in and energized circuit? - ✅✅✅0 voltage What should the voltage readings be across a good set of opened contacts in an energized circuit? - ✅✅✅The applied voltage What would cause a voltage drop across a set of closed contacts? - ✅✅✅Pitting or dirt Page 17 of 26 Which of the following would be preferred for a motor directly connected to a heavy blower wheel? - ✅✅✅Ball bearings What is the synchronous speed of a 6 pole motor? - ✅✅✅1200 RPM * Solution: synchronous speed = 120 x frequency number of poles 7200/6 = 1200 rpm Which of the following motor will produce the greater speed (RPM)? - ✅✅✅2 pole Which of the following motors has the best starting torque? - ✅✅✅Three phase If you double the RPM of a motor than the CFM will? - ✅✅✅Double If you double the RPM on a motor than the static pressure will? - ✅✅✅Square Page 20 of 26 If you double the RPM on a motor, then the horsepower requirement will? - ✅✅✅Cube What happens to the amp draw of a PSC motor as the external static pressure increases? - ✅✅✅The amp draw decreases What determines the actual operating RPM of a PSC blower motor? - ✅✅✅The external static pressure of the system They run capacitor is wired__ - ✅✅✅In series with the run winding The coil of a potential relay is wired__ - ✅✅✅Between the start and the common The primary reason for performing a duct traverse, would be to determine what? - ✅✅✅The average volume or CFM of the air in the duct The velocity of the air leaving a residential side wall register should be limited to: - ✅✅✅600 FPM Page 21 of 26 One making a flare on the end of copper tubing, the forming con should be moved into the tubing: - ✅✅✅In a back-and-forth motion Tube bender should only be used on? - ✅✅✅Soft copper tubing Which of the following tools should be used to cut capillary tubing? - ✅✅✅A triangle file A brazing flux is required whenever you are brazing: - ✅✅✅Copper to brass Which of the following produces the higher flame temperature? - ✅✅✅Oxyacetylene The two gauges on oxygen and acetylene tanks indicate what? - ✅✅✅The tank pressure and the outlet pressure When breezing with Oxycetylene the flame should be adjusted to be: - ✅✅✅Neutral Page 22 of 26 What is the most important points made by the following: There are many factors that contribute to comfort in a home or building. Temperature, humidity and cleanliness of the air are just a few examples of these factors. - ✅✅✅Comfort requires more than temperature control 10 is what percent of 30? - ✅✅✅333.33% * Solution: 10/30 x 100 = 33.33 Any pressure measured by a liquid or gas on a surface is typically measured: - ✅✅✅Using the same unique pressure scale as the bureau of standards How should one care for their hand tools after use? - ✅✅✅Clean and wipe often Lever type tubing bender's are best used for: - ✅✅✅Soft copper tubing Page 25 of 26 Capillary tube and should only be cut to the length using a: - ✅✅✅Triangular or knife edge file A hacksaw should never be used to cut copper tubing because: - ✅✅✅Saw chips can remain inside of the tubing Page 26 of 26