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HVAC FUNDAMENTAL FINAL EXAM questions and answers 2025-2026(latest update ), Exams of Biology

HVAC FUNDAMENTAL FINAL EXAM questions and answers 2025-2026(latest update with verified solutions).docx

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2024/2025

Available from 01/03/2025

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HVAC FUNDAMENTAL FINAL

EXAM questions and answers

2025-2026(latest update with

verified solutions)

What is the maximum amount of refrigerant that a recovery cylinder should contain? - answer 80% water capacity by weight During push-pull liquid recovery, vapor refrigerant is pulled from the __ - answer recovery cylinder If the entire refrigerant charge has leaked out of a system, then a __ should be used to pressurize the system to test for leaks - answer inert gas Which evacuation method involves charging a system with nitrogen to absorb moisture? - answer Triple evacuation When charging a system with refrigerant, the technician should put the low- and high-side service valves in ______. - answer mid- position What is the superheat of a system if the refrigerant temperature in the suction line is 58 degrees, its pressure in the evaporator is 60 psig, and its temperature in the evaporator is 34 degree F? - answer 24 degrees F The process of pumping a system's entire refrigerant charge into the liquid receiver is called a __________. - answer pump-down

Many recovery cylinders use a(n) ____________ as a safety device to turn off the recovery machine when the cylinder is 80% full. - answer liquid level switch Calculate the tare weight of a cylinder if its total weight is 590 lb and the weight of refrigerant in the cylinder is 450 lb - answer 104 lb Subcooling refers to the amount of ____ removed from a refrigerant after it has condensed. - answer sensible heat Pressure that is greater than atmospheric pressure is referred to as _______ pressure. - answer positive Two-part epoxy resin kits usually include one tube filled with epoxy and another tube filled with a(n) ______________. - answer hardener An evaporator that depends on gravity for air circulation is a _______ evaporator. - answer natural-draft A liquid-cooling evaporator ___________. - answer All of the above Heat exchangers made from two metal sheets that are welded together to form a series of passages are ___________ evaporators. - answer plate Heat exchangers featuring metal fins of various styles and types connected to evaporator tubing are ______ evaporators. - answer fin-and-tube Surfaces in and along air ducts that direct airflow through the evaporator and throughout the cabinet are called ______. - answer baffles

The baffles used in an evaporator _________. - answer All of the above A defrost timer that turns on defrost operations at a preset time and ends the defrost operation at a present time is a _____ defrost timer. - answer time-initiated, time-terminated A defrost timer that turns son defrost operations at a preset time and stops defrosting operations when the evaporator reaches a preset cut-out temperature is a ________ defrost timer. - answer time-initiated, temperature-terminated A defrost timer that turns on defrost operations at a preset time and turns it off when a preset pressure is reached is a ______ defrost timer. - answer time-initiated, pressure-terminated A condensate pump is used to __________. - answer remove the moisture that builds up from defrosting and condensation In a nonfreezing solution defrost system, ________. - answer All of the above Which of the following statements regarding water defrost systems is false? - answer Water delivery may be done during a cooling cycle with the compressor running. An electric heat defrost system __________. - answer energizes electric heating coils In what type of defrost system is air from the conditioned space circulated over the evaporator when the compressor is not running?

  • answer Off-cycle defrost system

Which of the following statements regarding off-cycle defrost systems is false? - answer It can only be used in very-low- temperature systems In what type of defrost system is hot refrigerant gas diverted to the evaporator to expedite the defrosting process? - answer None of the above Since a compressor continues to operate after a pump-down solenoid closes, ____________. - answer refrigerant from the evaporator and low side is pumped down In a hot-gas defrost system, the evaporator is defrosted by _________.

  • answer refrigerant vapor from the discharge line A condenser that uses only the air movement of either natural convection or forced drafts to remove heat from a system's refrigerant is a(n) _________ condenser. - answer air-cooled A condenser that uses only water as the medium into which system heat is expelled is a(n) __________ condenser. - answer water-cooled Some types of water-cooled condensers use _________. - answer the bottom part of the shell as a liquid receiver A condenser in which a water tubing winds around the inside of a metal refrigerant shell is called a(n) _______ condenser. - answer shell-and-coil A condenser that consists of an inner tube thorough which water flows in one direction and a surrounding outer tube through which

refrigerant flows in the opposite direction of the water flow is a ________. - answer tube-within-a-tube In a tube-within-a-tube condenser, _________. - answer Both A and B Counterflow in a tube-within-a-tube condenser allows _________. - answer All of the above A hot-water reclaim tank is a cylinder filled with water that absorbs heat from refrigerant flowing through a refrigerant system's ___________. - answer discharge line A tank connected between the outlet of a condenser and a liquid line that is used for refrigerant storage is a(n) ____________. - answer liquid reciever A suction line-liquid line heat exchanger ____________. - answer superheats vapor refrigerant in the suction line The superheating done by a suction line-liquid line heat exchanger helps prevent __________. - answer liquid slugging in the compressor The conditions that are normally maintained in an indoor space are known as the indoor __________. - answer climate The science of studying the thermodynamic properties of air and water vapor is called ____________. - answer psychrometry The long-term weather trends for a region are known as the __________. - answer climate

The ______________ is the layer of the atmosphere that is closest to the earth. - answer troposphere The _________ is the layer of the atmosphere that contains the ozone layer. - answer stratosphere The ______ is the outermost layer of the earth's atmosphere. - answer exosphere Which of the following statements about air pressure is false? - answer Air pressure increases as altitude increases Air with a relative humidity of 25% contains _________ of the moisture it is capable of holding. - answer one-fourth The desirable temperature for human comfort is ___________. - answer 72 degrees F (22* C) The vertical lines as shown in red on this psychrometric chart indicate ___________. - answer dry-bulb temperature The arcing lines as shown in red on this psychrometric chart represent the ___________. - answer constant relative humidity levels The slanted lines as shown in red on this psychrometric chart represent the _________. - answer constant specific volumes The __________ is the amount of heat that affects the air temperature compared to the total heat added to or released from the air. - answer sensible heat ratio

The volume of air flowing through a duct is calculated by multiplying air __________ by the cross-sectional area of the duct. - answer velocity If air flows through an occupied space at more than ________, occupants of the space will feel a draft. - answer 15' to 20' per minute (4.5m/min to 6m/min) A __________ anemometer measure airflow velocity using a small propeller. - answer vane A _________anemometer operates on the principle that incoming air will cause a deflection at different angles as the air velocity changes. - answer swinging-vane _________ anemometers can be used in environments where electronic meters pose an explosion risk. - answer Swinging-vane Total air pressure is the static air pressure plus the __________ pressure. - answer velocity The outer tube of a pitot tube has holes on the side and measures only the __________ pressure. - answer static The difference between the total pressure and the static pressure is the _________ pressure. - answer velocity Air pressure for the sake of air velocity is measured in inches of ____________. - answer water During the cooling season, cold air _____________. - answer All of the above

During the heating season, warm air rises and ____________. - answer All of the above Passive recovery is generally used on larger systems. - answer False Zeotropic refrigerant blends should be charged as a liquid. - answer Ture The amount of refrigerant that a cylinder can safely hold 90% of the volume of water that it can hold. - answer False A system should have low-pressure flowing nitrogen within before a leak is fixed by brazing. - answer True Two-part epoxy resins must be heated in order to harden. - answer False Longer vacuum pump service lines are more effective at pulling a vacuum than shorter service lines. - answer False To release refrigerant dissolved in compressor oil, an oxyacetylene torch should be used to heat the compressor. - answer False Vapor recovery must be used in combination with liquid recovery to recover a system's entire refrigerant charge. - answer True Push-pull liquid recovery should not be used in systems with less than 5 lb of refrigerant charge. - answer True

The refrigerant charge in a system with a fixed orifice metering device should be checked by subcooling. - answer False Active recovery uses an HVACR system's compressor to pump refrigerant into a recovery cylinder. - answer False Air-cooling evaporators are used directly cool the air within a conditioned space. - answer True In a commercial cooler using a forced-draft evaporator system, the evaporator's fan motor may run continuously. - answer True Some commercial refrigerant applications require that water be kept from freezing at temperatures below 32F (0C) - answer True A sweet water bath is composed of 20% glycol and 80% tap water. - answer False Some water defrost systems spray a lithium chloride brine solution over the evaporator. - answer True An off-cycle defrost system can only be used if the air in the conditioned space remains within five degrees of freezing. - answer False Closing the condenser housing louvers can be used to raise low head pressure in low ambient temperatures. - answer True When liquid line refrigerant is subcooled more than usual, system efficiency increases. - answer True

A limited amount of flash gas created in the liquid line increases a system's efficiency. - answer False If the ambient air temperature is warmer than 98.6F (36C), air movement cools the human body. - answer False If the heating system provides over 2.5 to 5 feet per minute (fpm) of air movement, a temperature increase may be necessary to maintain comfort. - answer False The less dense air is, the less its specific volume. - answer False Warm air holds more moisture than cold air. - answer True Cold air holds more moisture than warm air. - answer False Dry air causes rapid evaporation, cooling surfaces quickly. - answer True Humidity controls are used to add humidity in cold weather and remove moisture in hot weather. - answer True Dry-bulb temperature does not take into account the effect of humidity in the air. - answer True Wet-bulb temperature is always higher thank dry-bulb temperature.

  • answer False If air is very moist, evaporation from the moist wick of a wet-bulb thermometer will be relatively slow. - answer True

The numeric value of the heating or cooling degree days equals the difference between the average temperature that day and 65F (18C). - answer True To ensure an accurate reading, airflow over a wet-bulb thermometer should be quite slow. - answer False Latent heat changes the temperature of air and sensible heat changes the level of humidity. - answer False A technician can measure air pressure inside of ductwork using a pitot tube and an inclined manometer. - answer True Velocity pressure can be measured by bringing airflow to a stop inside a manometer. - answer True Turbulent airflow affects the ability of a pitot tube to accurately measure pressures. - answer True To ensure precise measurements, air straightening vanes should be located upstream from a pitot tube. - answer True Sensible heat changes the temperature of the air and latent heat changes the level of humidity. - answer True A certain amount of air movement is needed in a room to prevent stratification. - answer True Surfaces designed to radiate heat are more efficient if they are painted with a light color rather than a dark color. - answer False

The amount of heat added to a refrigerant after it has evaporated is called ______________. - answer superheat Recovery machines are not used during ______________ recovery. - answer passive To prevent contaminates from damaging a recovery machine's compressor, an in-line ________________ is placed between the system and the machine's inlet. - answer filter drier If a system is unable to hold a vacuum, them the system has a(n) _____________. - answer leak When condensation cannot flow directly to a drain, a(n) __________________ can be used to move it to the drain. - answer condensate pump Adding refrigerant to a system is called ___________ the system. - answer charging In a reverse cycle hot-gas defrost system, the evaporator acts as a(n) ______________ during defrost. - answer condenser 113-117 CHECK REVIEW - answer REVIEW NA - answer NA NA - answer NA NA - answer NA

NA - answer NA NA - answer NA NA - answer NA NA - answer NA The layer of the atmosphere that contains the ionosphere. - answer Thermosphere The air surrounding the earth. - answer Atmospherer The long-term weather trends for a region. - answer Climate The layer of the atmosphere that contains the ozone layer. - answer Stratosphere Represents how warm the combination of humidity and temperature feels to the occupant of a space. - answer Equivalent temperature An invisible, odorless, and tasteless mixture of gases. - answer Air The presence of moisture or water vapor in the air. - answer Humidity The layer of the atmosphere closest to the earth. - answer Troposphere The outermost layer of earth's atmosphere. - answer Exosphere

Conditions in the atmosphere including temperature, wind velocity and direction. - answer Weather A gaseous element occupying 3/4 of the earth's atmosphere. - answer Nitrogen A gaseous element occupying 23% of the earth's atmosphere. - answer Oxygen An inert noble gas that comprises approximately .93% of the atmosphere by volume. - answer Argon Absorbed by growing plants and one of the building blocks in the development of plant cells. - answer Carbon dioxide A very light gas that is present in most fuels and does not show in weight percentage. - answer Hydrogen The most common gaseous contaminant that is formed by combustion of fuels. - answer Sulfur dioxide A substance that absorbs moisture from the air. - answer Desiccant The amount of the heat that affects the air temperature compared to the total heat added to or released from the air. - answer Sensible heat ration An instrument that measures moisture in the air. - answer Hygrometer

A measure used to indicate the heating or cooling needed for a given region. - answer Degree days The amount of heat required to raise the temperature of one pound of air 1F, or one kilogram of air 1C. - answer Specific heat The total heat content in an air sample. - answer Enthalpy Air brought in from the outdoors. - answer Makeup air A surface that absorbs radiant heat. - answer Heat sink The combined effect of temperature and wind speed. - answer Windchill index Air velocity measuring instrument that operates on deflection at different angles. - answer Swinging-vane anemometer A velocity measuring instrument that uses a temperature-sensitive wire element. - answer Hot-wire anemometer A measuring instrument that compares two different pressures. - answer Manometer An air velocity measuring instrument that uses a small propeller. - answer Vane anemometer Changing the air in a building. - answer Ventilation