HVAC Controls 26408-23 Practice Test

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