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Questions And Answers
What are the most common motor controls in HVACR?
correct answer ✅1. Contactor
- Relay Who sets the standards of all electrical installations and over current protection? - correct answer ✅National Electric Code (NEC) What do loose belts have a tendency to do that will negatively affect motor operation? - correct answer ✅Slip What is the max rated amperage for the secondary of this transformer? Input Voltage = 120 Secondary Voltage = 26 VA rating = 40 Round answer to the tenth position. - correct answer ✅1.
Questions And Answers
Which of the following is an example of a load? - correct answer ✅1. Solenoid
- Motor
- Resistor What is the max rated amperage for the secondary of this transformer? Input Voltage = 220 Secondary Voltage = 120 VA rating = 75 Round answer to the tenth position. - correct answer ✅0. What are the most common types of wire diagrams used in HVACR? - correct answer ✅1. Ladder
- Pictorial What voltage would you read between points 1 and 10? Answer only 0, 24, 120 or 230 please. - correct answer ✅ 230
Questions And Answers
- 120 volts
- Single phase
- One hot (L1), a Neutral and a Ground What voltage would you read between points 2 and 3? Answer only 0, 24, 120 or 230 please. - correct answer ✅ 0 What are the four types of problems in HVACR - correct answer ✅1. Mechanical and Electrical
- Mechanical
- Operator Error
- Electrical What voltage would you read between points 3 and 8? Answer only 0, 24, 120 or 230 please. - correct answer ✅ 230 What voltage would you read between points 7 and 10?
Questions And Answers
Answer only 0, 24, 120 or 230 please. - correct answer ✅ 0 Service Call The technician arrives at the call and talks with the customer who says that their furnace is not heating the space and they do not notice air coming from the registers. The technician then proceeds to the furnace under the house. The furnace is hot to touch on arrival. The technician hears the burner ignite and watches it for a few minutes. The burners shut off after a couple minuets and the technician can hear the blower humming. The motor is a PSC and spins freely, ohms out properly, the bearings feel normal and is very hot to touch. What could be the problem? - correct answer ✅The capacitor is bad causing the motor to struggle to start and over heat. Service call The technician arrive at a business with a package system. The technician talks with the customer who states that the system will not cool the space. The technician proceeds to the thermostat and switches
Questions And Answers
What is the net oil pressure? Liquid pressure = 255 psig Suction pressure = 126 psig Oil pump outlet pressure = 136 psig - correct answer ✅ 10 Which of the following is an example of a control? - correct answer ✅1. Switch
- Thermostat
- Contactor What happens in the condenser? - correct answer ✅1. Subcool refrigerant
- Desuperheat refrigerant
- Condensing of refrigerant When is the greatest amount of heat transfered out of the refrigerant? - correct answer ✅Change of State
Questions And Answers
R410a System High pressure 335 psig Low Pressure 145 psig Liquid line temp 95oF Suction line time 67oF What is the subcooing? - correct answer ✅ 10 What is the condition that an evaporator is considered to be in when it is receiving too much refrigerant? - correct answer ✅Flooded In a belt driven compressor what is the pulley on the motor called? - correct answer ✅Drive Pulley What is the condition that an evaporator is considered to be in when it is not receiving enough refrigerant? - correct answer ✅Starved What is the compression ratio? (Answer to ONE decimal place)
Questions And Answers
- Undersized duct system R410a System High pressure 276 psig Low Pressure 122 psig Liquid line temp 84oF Suction line time 51oF What is the superheat? - correct answer ✅ 10 What is the compression ratio? (Answer to ONE decimal place) Discharge pressure = 201 psig Suction pressure is = 67 psig ?:1 - correct answer ✅2. What happens in the evaporator? - correct answer ✅1. Superheating of refrigerant
- Boiling of refrigerant
Questions And Answers
System: TXV Target Superheat: 10°F ± 2°F Evaporator Saturation Temperature: 45°F Vapor Line Temperature: 53°F Target Subcooling: 15°F ± 3°F Condenser Saturation Temperature: 120°F Liquid Line Temperature: 105°F Is the charge UNDER, OVER or CORRECT? - correct answer ✅Correct What are the types of compressors? - correct answer ✅1. Reciprocating
- Rotary
- Centrifugal
- Screw
- Scroll In a belt driven compressor what is the pulley on the compressor called? - correct answer ✅Driven Pulley
Questions And Answers
Target Superheat: 10°F ± 2°F Evaporator Saturation Temperature: 45°F Vapor Line Temperature: 53°F Target Subcooling: 15°F ± 3°F Condenser Saturation Temperature: 120°F Liquid Line Temperature: 98°F Is the charge UNDER, OVER or CORRECT? - correct answer ✅Over What expansion device is charged using superheat? [a] What expansion device is charged using sub-cool? [b] - correct answer ✅A. Fixed bore or Piston or Capillary Tube B. TXV Or
Questions And Answers
Thermostatic Expansion Valve What listed below can lead to a overloaded evaporator? - correct answer ✅1. Undersized system for heat load
- Attic air infiltrating into return duct
- Too many occupants
- Started up after repair on hot day What are the symptoms of a Fixed Orifice system operating in the cool mode that has a leak (Undercharged)? - correct answer ✅1. Low Subcooling
- Low Head Pressure
- Low Compressor Amps
- Low Suction Pressure
- High Superheat Please select ALL of the SAFETY components common to a gas furnace - correct answer ✅1. Door switch
- Pressure switch
Questions And Answers
Natural: [b] inwc - correct answer ✅A. 11 B. 3. What component transfers heat to room air and is a barrier that separates combustion gases from room air in a gas fired furnace? - correct answer ✅Heat Exchanger A draft with a fan that blows flue gases through the heat exchanger is called? - correct answer ✅Forced Draft List the four types of ignition systems. 1.[a] 2.[b] 3.[c] 4.[d] - correct answer ✅A. Standing Pilot B. Intermittent C. Spark D. Hot Surface
Questions And Answers
Calculate the BTUH and the temperature rise of a 7.5KW electric furnace with 1150 CFM of air flow. (enter whole number only) [a] BTUH [b] oF - correct answer ✅A. 25,598 BTUH B. 21 oF Calculate the BTUH and the CFM of a 5KW electric furnace with a 22 degree F temperature rise. (enter whole number only) [a] BTUH [b] CFM - correct answer ✅A. 17, B. 718 Give the proper sequence of operation in an electric forced air furnace. - correct answer ✅1. Call of Heat
- Sequencer energized
- Blower starts.
Questions And Answers
On a 90% efficiency furnace, what is the best way to inspect the heat exchanger? - correct answer ✅Through the evaporator coil section after the coil A plate is removed. A draft with a fan that sucks flue gases through the heat exchanger is called? - correct answer ✅Induced Draft From the list below select all the furnace components that should be cleaned or replaced on a maintenance.
correct answer ✅1. Inducer port
- Burners
- Spark igniter
- Flame sensor
- Furnace filters
- Orifices An electric furnace is operating on 225 volts and is drawing 83 amps. What is the heat out put of this
Questions And Answers
furnace? (round to whole number) - correct answer ✅63, The pipe that supplies gas to all burners evenly is called? - correct answer ✅Manifold No heat service call. A Service Technician arrives at a call and the homeowner states they can only get the fan running when the fan is set to the "on" position. The Service Technician set the thermostat to heat and starts a call for heat. The furnace is 6 years old 80% with induced draft and HSI ignition source. By the time the tech gets to the furnace the inducer is running but nothing else and the IFC is flashing 3 flashes indicating no flame. As he observes the furnace he reads 5.5inwc inlet gas pressure and a manifold pressure of 3.4inwc. It continues like this for another 5 minutes with the gas valve clicking every minute then shuts down still with 3 flashes. What could be the problem and how would a Service Technician prove that is the problem? - correct answer ✅Cracked HSI. Ohm out the HSI.
