HVAC Controls 26408-23 Practice Test

These questions are part of the practice quiz. Start practicing

• Which NEC article governs motors for refrigeration compressors when using conventional (nonhermetic) motors?
• In a heating system, with the fan switch set to AUTO, which motors run when the thermostat calls for heat?
• NEC Article 440, Part V covers
• Older conventional thermostats commonly contain which hazardous material requiring special disposal?
• Which control approach primarily uses microprocessors, sensors, and digital communication to manage HVAC equipment?
• What is setpoint creep and how can it be prevented?
• When you are installing a 24V thermostat, to which terminals of the thermostat should you connect the 24VAC power supply and what color wires would you use?
• Which three control strategies are commonly used in zone control for HVAC units such as AHUs, VAVs, or fan-coil units?
• The tubing that carries heat-laden refrigerant gas from the evaporator to the compressor is the
• What is the role of a damper actuator in a VAV system?
• What is the primary purpose of the defrost cycle in a heat pump?
• Trend log data records which of the following?
• During a defrost cycle, heat pumps melt ice on the outside coil using which heat source?
• What is the name of the limit switch that senses flame outside the heat exchanger?
• What is occupancy-based ventilation and how is it typically implemented?
• Why is a deadband typically implemented around the thermostat setpoint?
• What is the purpose of a lockout relay in a comfort cooling control circuit?
• Which sequence correctly describes a typical startup sequence for a chilled water plant?
• The type of digital control building system designed to serve multiple zones is the ________.
• According to NEC Section 440.7, the largest motor is considered the one that ________.
• Which option best describes HVAC safety interlock components?
• Which device can retain a high-voltage charge after power is removed?
• What is static pressure in a duct system and why is it monitored by controls?
• A good location for a thermostat is ________.
• The component in an air conditioning or refrigeration system to which the heat from the conditioned space or item being cooled is transferred to the refrigerant is the
• The Seebeck effect underlies which type of device?
• Which term describes the difference between the heating cycle's turn-on and turn-off temperatures in a thermostat?
• Economizer lockout is a control setting that does what?
• Which safety device is designed to detect flame rollout and open the circuit if flame is not contained?
• What is a sequence of operation (SOO) and why is it critical in commissioning?
• Why is sensor calibration important in HVAC controls?
• What is night setback and what energy benefit does it provide?
• Why is there a minimum outdoor air ventilation requirement in HVAC control?
• Multistage thermostats save energy by cycling on heating or cooling stages based on what?
• What distinguishes commissioning from recommissioning in HVAC controls?
• During a fire event, what is a key HVAC control action related to smoke control?
• Which component stores electrical energy and can retain a charge after power is removed?
• The thermostat terminal normally assigned to cooling control is which?
• What does a three-way valve do in a hydronic heating or cooling circuit?
• The term that describes heat moving from one location to another due to a temperature difference is known as what?
• Which instrument would you use to verify the voltage output of a temperature sensor that generates millivolt-level signals?
• The device that prevents automatic restart after a fault in cooling systems is called a
• In a chilled water plant startup, when should the chiller compressors be started relative to head pressure?
• Connecting a 120V heating cable to a 240V circuit will
• Why is a minimum damper position important in outdoor air control?
• Which device can retain a high-voltage charge after power has been removed?
• Differentiate between VAV and CAV systems.
• A device that uses dissimilar metals to control electron flow is known as a
• In the electrical control circuit of a cooling-only system, the outdoor fan motor ________.
• Describe a typical boiler startup sequence.
• Which statement lists the devices typically involved in HVAC safety interlocks?
• A heat anticipator is used in an electromechanical heating thermostat to ______.
• What is a deadband in thermostat control?
• For heat pumps, which characteristic is considered a required feature related to supplemental heat?
• Which two conditions typical factors in initiation of a defrost cycle in a heat pump?
• In the mechanical refrigeration cycle, the refrigerant leaving the evaporator is a ________.
• Conventional line-voltage thermostats are less precise because
• Why does a bimetal strip bend as the temperature changes?
• Heat pumps provide heat by reversing the cooling cycle.
• Which device is commonly activated by a thermostat call for heat in many HVAC systems?
• What is the primary objective of alarm management in a building automation system (BAS)?
• What is the value of setting up trend alerts and alarms in a BAS?
• A reset schedule reduces energy consumption by doing what?
• The R terminal in a standard thermostat wiring scheme is connected to the ______ of the 24V control transformer.
• How should HVAC controls coordinate with fire and life safety systems?
• The Seebeck effect is the principle behind which device?
• In the refrigeration cycle, which device raises the pressure of the refrigerant on the high-pressure side?
• Why do conventional line-voltage thermostats lack precise temperature control?
• Which fossil fuel is most widely used?
• Verifying OA mix during cooling coil troubleshooting ensures what?
• A limit control is a heat-actuated switch positioned above or beside ______.
• Which would be an optional feature for an air conditioning control system?
• What device uses dissimilar metals to generate a voltage proportional to temperature?
• Permanently installed energy storage systems are covered in NEC in
• What device prevents the compressor from re-starting immediately after shutdown due to pressure build-up?
• In a refrigeration system, which component rejects heat from the refrigerant to ambient air?
• What is ASHRAE 62.1 and what does it require for ventilation?
• Trend log data is best described as which of the following?
• In a refrigeration cycle, which component absorbs heat from the space being cooled?
• Which component primarily modulates zone cooling in a VAV system?
• Which digital control system is designed to serve multiple zones with varying air flow?
• Which device uses dissimilar metals to control electron flow?
• Which control strategy explicitly uses outdoor air modulation along with reheat or VAV to meet air-quality and temperature goals?
• Which scenario typically triggers recommissioning of HVAC controls?
• In an air-to-air heat pump, defrost is accomplished by switching to which mode?
• How does economizer damper control logic decide when to open or close?
• Which instrument is used to check the output of a thermocouple?
• What is a reset schedule in HVAC controls?
• Compare pneumatic controls with electronic controls in HVAC systems.
• When a typical heat pump is operating in defrost mode, what usually happens indoors?
• Which device delays the furnace blower startup to improve efficiency?
• Which device is connected to the G terminal in a typical thermostat circuit?
• A conventional thermostat should not be thrown into the regular trash because it
• The NEC requirements for fixed electric space-heating equipment are covered in which NEC article?
• What is BACnet and why is it important in HVAC controls?
• What component staggers electric heater startup to prevent circuit overload?
• The provisions for room air conditioners are referenced in ________.
• What is the purpose of a pressure sensor in a hydronic system?
• Which practice benefits most from having a clearly defined sequence of operation (SOO)?
• How does a variable frequency drive (VFD) affect energy use in fans and pumps?
• Which of the following options lists the four basic refrigerant circuit components used in a cooling/refrigeration system?
• When refrigeration compressors are driven by conventional (nonhermetic) motors, the motors and controls are subject to the requirements in
• The function of a heat sequencer is to _________.
• What is a disadvantage of a bimetal thermostat when compared to an electronic thermostat?
• Which control voltages are commonly used for field devices and why is voltage compatibility important?
• In a modern building automation system, which statement best describes the field controller's scope?
• What prevents an automatic-changeover thermostat from cycling back and forth between heating and cooling?
• How does demand limiting improve building energy performance?
• The key to successful control system is the integration of the ___________ and the _____________
• The differential in an automatic-changeover thermostat is _______.
• If the IFR operates and the fan starts when the thermostat fan switch is set to On, and the relay operates when the switch is set to Auto, the most likely cause is a defective ___________.
• What could be a consequence of not monitoring static pressure in a duct system?
• How do owner requirements (OPR) and basis of design (BOD) influence control strategies?
• In heat pump systems, what feature adds extra heating by design?
• The pressure-based control in a gas furnace heat exchanger is used to verify that which component is operating correctly?
• What is the main difference between open-loop and closed-loop control in HVAC systems?
• Which component stores energy in an electric field and is commonly used in motor control circuits?
• In the described bimetal strip, which metals form the bonded pair?
• What are the three basic elements of a control loop?
• In the thermostat wiring, which terminal is used for the heating control?
• What does a "lockout" mean in an HVAC control sequence?
• The abbreviation FLC in electrical design stands for
• What is the difference between a 2-position valve and a 3-position valve?
• The NEC section that specifies the location and accessibility of air conditioning equipment disconnects is
• The purpose of a control that monitors the pressure in a gas furnace heat exchanger is to verify what?
• The purpose of a compressor short-cycle timer is to __________.
• The recommended installed height for a thermostat is
• A freezestat is best described as which type of switch?
• In a heat pump, which thermostat terminal is typically connected to the reversing valve control?
• What is the function of an Analog Input in a BACnet-enabled HVAC control?
• In a standard thermostat wiring scheme, the heating control is wired to terminal
• In a modern building automation system, which statement best describes the role of a field controller?
• When is reheat used in a VAV system?
• What device acts as a safety shutoff by responding to temperature changes to prevent equipment overheating in HVAC systems?
• Where should temperature sensors be placed for accurate control and why?
• The G terminal would be connected to the _________.
• If the compressor motor, OFM, an indoor fan motor (IFM) all fail to operate on a cooling call, the most likely cause __________.
• Conductor sizing for multiple hermetic compressors must include total load plus what percentage of the largest motor's full-load current?
• A defective lockout relay should be replaced with an exact duplicate, sometimes called what?
• What is the difference between a digital signal and an analog signal?
• Which component is used to filter and store energy in motor circuits, helping reduce voltage spikes?
• Which thermostat terminal is commonly used for cooling control?
• Which principle states that heat is created in one place and carried to another by means of air or water?
• Which statement accurately describes the disconnecting requirement for heating equipment?
• In a closed-loop HVAC control, what happens when the sensor detects deviation from the setpoint?
• What is the purpose of interlocks in HVAC control systems?
• In BACnet terms, what is the difference between Analog Input and Binary Input?
• Which occurs as soon as a heating thermostat is closed?
• Which description best matches a VAV with zone sensing control?
• Which of the following is an example of an external analog device?
• What is the primary benefit of a two-pump configuration in a chiller plant (primary/secondary pumping)?
• Name two occupancy sensing technologies used in HVAC controls.
• Which action helps control condenser head pressure in a cooling system?
• Which refrigerant path carries high-pressure vapor from the compressor to the condenser?
• The heat anticipator in a heating-only thermostat is a(n) ____________ in series with ____________.
• How do CO2 sensors contribute to IAQ-based ventilation control?
• Which of the following is NOT one of the four basic refrigerant circuit components?
• In the short cycle timer circuit, the yellow wire from the thermostat to the timer is connected to terminal _________.
• What is the minimum interlock setting on automatic changeover thermostats commonly called?
• Which statement best describes the metals used in the described bimetal strip?
• Heat pumps provide heat by ________.
• What is the primary purpose of a damper actuator in a VAV system?
• Which of these causes could be immediately eliminated if a compressor is defective?
• Which factors influence condenser head pressure in a cooling system, and how is it controlled?
• Thermostats with bimetal sensing elements typically use a combination of copper or brass and which alloy?
• Which statement best describes a freezestat?
• Low-voltage (24VAC) control circuits are used in HVAC systems because __________.
• A device that generates a voltage proportional to temperature difference is called a
• In a hydronic heating system, what is the heat transfer medium?
• Which of the following would be considered a digital device?
• What is the purpose of a high-limit switch?
• Why is regular sensor calibration and maintenance essential for controls?
• In a boiler system, what is the heat exchange medium?
• The device that provides the pressure drop that lowers the boiling point of the refrigerant in a refrigerant circuit is the __________.
• Which statement correctly describes why a bimetal thermostat responds to temperature changes?
• What is the primary purpose of a Basis of Design (BOD) document in HVAC projects?
• What is NFPA 90A and how does it relate to HVAC controls?
• What is a standard installation height for a thermostat on an interior wall to ensure accurate sensing?
• Which thermostat terminal is most commonly used to energize the reversing valve in a heat pump?
• What is the defrost cycle used to prevent in a heat pump's outdoor coil?
• In BACnet terms, what is the difference between Analog Output and Binary Output?
• Which device delays the furnace blower startup to increase efficiency?
• What is primary/secondary pumping in a chiller plant used for?
• If a mercury thermostat seems out of adjustment, what is the first step?
• Which statement about thermostat installation height is true?
• In IAQ-based ventilation, which parameter is commonly used to determine the need for outdoor air?
• What is the purpose of logging events in alarm management within a BAS?
• In a standard thermostat wiring scheme, the R wire originates from the __________.
• Which NEC article addresses permanently installed energy storage systems?
• The rating of cord- and plug-connected room air conditioners must not exceed what percentage of the branch circuit rating when lighting units are also supplied?
• Which steps are part of a troubleshooting approach if a cooling coil fails to deliver expected cooling?
• In economizer operation, what is the effect when outdoor air conditions are favorable?
• In a mechanical refrigeration circuit, what is the purpose of the evaporator?