BOMA-HVAC EXAM QUESTIONS LATEST UPDATE 2024/25 WITH 100% DETAILED VERIFIED ANSWERS., Exams of Health sciences

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BOMA-HVAC EXAM

QUESTIONS LATEST UPDATE

2024/25 WITH 100% DETAILED

VERIFIED ANSWERS.

The man whose work is considered the real beginning of the science of air-conditioning _____. Willis Carrier Psychrometry refers to the relationship between _____ and _____. Humidity; air The amount of moisture in the air compared to how much it can hold is _____. Relative humidity The human bodies well being depends upon the _____. Bodies metabolism The device used to determine the moisture content of air is the _____ psychrometer Of the fuels listed the one that is the most efficient is _____. Gas The effective temperature takes into consideration the effect of _____ and _____. Humidity; temperature Air conditioning is the control of the _____, _____, _____ and _____. Temperature, humidity, purity and distribution of air.

The element that makes up the greatest percentage by volume of air is _____. Nitrogen Steam gives off a great amount of heat because of its _____. Specific heat The velocity of air moving thru a fan system is expressed in _____. Feet per minute What volume of air will move thru a duct 24x18 at velocity of 450 feet per minute? 1350 cfm The following types of fans are classified as centrifugal fans. Forward curved, radial and backward curved Select the statement that does not apply to backward inclined fans. Has an overloading BHP horse power curve. The quantity of air moving thru a fan system is expressed in _____. Cubic feet per minute The instrument used to measure air pressure in duct is the _____. Monometer Air flow thru a duct has the highest _____. Velocity near the center of the duct. Select the statement which does not apply to the fan laws. Static pressure in a duct increases as the velocity decreases. Variable air volume system feature is _____. Varies the volume of air with space temperature conditions Double duct systems are _____.

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The purpose of a primary control is to _____. Start or stop the system A pressurestat responds to _____. System pressure The oil safety switch is operated by _____. Oil pressure A low limit control _____. ? A high limit control _____. ? Limit controls _____. Are wired into the circuit in series A diulating switch is used to _____. Change proportional action to two position control. A ratio relay is used to _____. Provide sequence control of more than one actuator. A proportional control: Where a movement from the set point produces a proportional movement of the actuator A three way diverting valve: has two outlets and one common inlet Heat will continue to flow between two bodies until they have the same amount of _____. Sensible heat Heat which causes a change of state is _____.

Latent heat The refrigeration effect of a refrigerant is improved by _____. Subcooling the liquid. In the refrigeration cycle, the medium that picks up the heat is the _____. refrigerant. A heat exchanger _____. Subcools the liquid refrigerant Calculations involving heat load of people takes into consideration heat due to _____ and _____. Latent heat; sensible heat The flow control device used to maintain system temperature is the _____. Evaporator pressure valve Enthalpy refers to the _____. Heat content of the refrigerant The metering device is designed to _____. Control flow of refrigerant The evaporator pressure regulator (EPR). Limits evaporator pressure Assume a centrifugal unit with R11 is operating at 8.8 PSIG condensing pressure and 86 degrees condensing temperature, what is the partial pressure due to air? 5.6 (see chart) Utilizing the values in the above problem, what is the partial pressure due to the refrigerant? 3.2 (see chart) The most efficient method of capacity control is by the use of _____.

Speed control The pump out unit: is used to transfer the refrigerant to an external receiver. The movement of the pre-rotation vanes is controlled by the _____. Chill water temperature control. The device that would limit the opening of the prerotation vanes on start up is the _____. Load limiting mechanism Prerotation vanes are used to control _____. Capacity The function of the economizer is to _____. Increase the refrigeration effect. Economizers: for the same power input, capacity is increased The least likely cause at high suction pressure would be _____. Not enough system load A psychometric chart is a graphic representation of _____? Thermodynamic properties Enthalpy refers to the _____? Measure of energy content of a substance Which of the following natural laws has the least bearing on the science of air conditioning? Boyle's law, Charle's Law & Dalton's Law. What is an excellent heat carrier because it _____? Has high specific heat

The element that makes up the most percentage of air is _____? Nitrogen The quantity of air moving through a fan system is expressed in _____? Cfm The dry bulb temperature is _____? The room temperature taken by an ordinary thermometer. It is commonly held that a relative humidity of _____ percent is desirable? 30 to 50 percent. The heat absorbed after the refrigerant has vaporized becomes _____? Superheated The heat required to melt 1 pound of ice at 32 degrees to water at sea level is equal to _____? 144 BTUs The temperature of which boiling takes place in any liquid is called the _____? Saturation temperature The low side float is controlled by the _____? Evaporation of refrigerant in the evaporator When chemically cleaning a water system which has scale, which of the following chemicals should be used? Inhibited acid _____, _____, _____ & _____ is the refrigeration cycle? Expansion; evaporation; compression & condensation The expansion or contraction of a gas without a change in temperature is known as _____? Adiabatic

Refrigeration effect takes place in the _____? Evaporator The heat picked up by the evaporator is the heat _____. Given up by the medium or product being cooled. In a mechanical refrigeration system, the compressor is located between the _____ and _____? Evaporator and condenser For practical purposes the low side of a refrigeration system includes the _____? Evaporator What is the primary surface and the secondary surface in an evaporator coil? Tubes are primary, fins are secondary The 2 classification of compressors are called? Positive displacement and kinetic displacement A 230 volt PFC compressor tries to start at 184 volts and trips on overload protection, the starting torque of the motor is _____? Decrease by lower voltage What is the advantage of a flooded type evaporator? Provides better heat transfer The use of a mechanical shaft seal is necessary in an _____? Open type compressor The heat rejected by the condenser is the heat of _____? Compression and the heat absorbed by the evaporator In a centrifugal chiller, the purge unit is used to _____? Remove non-condensibles from the condenser

A single way to distinguish a capacitor for a DC circuit from one AC circuit is to _____? check for polarity markings on the circuit The automatic expansion valve is controlled by _____? Evaporator coil superheat The automatic expansion valve controls _____? The evaporator pressure A liquid line heat exchanger _____. Subcools liquid refrigerant Which type of expansion valve is seldom used for refrigeration systems? Hand operated The liquid line on a refrigeration system connects the following components. Receiver and metering device A thermal electric expansion valve is controlled by a _____? Thermistor Receivers should be large enough to _____. Store the system charge An accumulator prevents slugging because it separates _____ and _____. Vapor and liquid refrigerant Moisture _____ restricts the filter drier? will As refrigerants temperature increases the rate of heat transfer? Decreases A heat exchanger in a refrigeration system?

Subcools the liquid refrigerant Economizers on centrifugal chillers? The capacity is increased for the same power input Which of the following is true for cylinder head bypass as a means of capacity control in a multi- cylinder compressor type refrigeration system? A check valve is used to separate inactive cylinders from active ones The expansion valve is a _____ device which controls the flow of liquid refrigerant to the evaporator coil under varying load conditions? Metering The speed of air through a duct is measured in _____? Feet per minute When wet bub and dry bulb temperatures are the same, this indicates a relative humidity of _____? 100 A A/C system with zone control is obtained by mixing hot and cold air at the central unit in response to room thermostats is a _____ system? Multi-zone The speed of a centrifugal compressor as compared to reciprocating compressors is _____? Much higher In commercial buildings, heat generated by lights does not seriously affect control of the heating system? False Outside air may get into air conditioned spaces by _____? Infiltration through walls, infiltration through swinging doors and air introduced to replace exhausted air. The most common type of heat pump used is the _____ heat pump.

Air to air What type of fan is mostly used in HVAC and industrial systems? Centrifugal