HVAC Controls 26408-23 Practice Test

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