Master Mechanical License Practice Test

These questions are part of the practice quiz. Start practicing

• What impact does a dirty air filter have on a gas furnace?
• Which of the following does NOT cause flashback in a gas-fired heating unit?
• Which of the following types of boilers does NOT require valves in their supply and return lines?
• What does the term "BTU" stand for, and what does it measure?
• For optimal oil return from the evaporator to the compressor, how should the refrigerant suction line be designed?
• Why should exhaust systems be maintained regularly?
• What is the primary purpose of a vapor barrier?
• What are the primary components of a refrigeration cycle?
• What is the main function of the evaporator in a refrigeration system?
• What does a measured superheat of 10°F indicate about a thermostatic expansion valve?
• What is the minimum test pressure for a fuel gas system designed to operate at 2 psi?
• How many BTU/h does it take to heat 1 gallon of water from 55F to 120F, given 1 gallon of water weighs 8.33 lbs?
• What is the purpose of a mechanical contractor's license?
• For a 15 KW furnace on a 240 V system, what will be the approximate electric load?
• A floor furnace can be installed under all the following conditions EXCEPT:
• What does an air conditioning system primarily do in terms of humidity control?
• What is the purpose of a backflow preventer in plumbing systems?
• What is the primary purpose of a gas valve in a heating system?
• What does a modulating gas valve in a furnace respond to in order to change the burner flame?
• The duct system of a 7.5 ton package heat pump should be designed for what normal airflow?
• Why is purging necessary before brazing copper pipes?
• How many threads per inch are cut on a 1-1/2 inch black steel pipe?
• What is a common symptom of low refrigerant charge in an air conditioning system?
• What is the maximum permitted length for a metal flex line to a residential furnace?
• What occurs with an increase in moisture content of the air while the dry bulb temperature remains constant?
• What is the primary use of a thermal relay?
• What does a central HVAC system typically use?
• What is the commonly recommended minimum air exchange rate for residential buildings?
• What is an advantage of a water-cooled condenser compared to an air-cooled condenser?
• What is the wet bulb temperature of the air mixture entering the coil?
• What is likely wrong with a compressor if the resistance readings show infinite resistance from common to run and common to start?
• In a step-down transformer with a primary coil of 10 turns and a secondary voltage of 48 volts, how many turns does the secondary coil have?
• What is an important consideration when designing a ventilation system?
• What must not occur when reusing cylinders that contain oxygen or acetylene?
• For a blower type furnace, how many square inches of free air are required per 1,000 BTU of the furnace's rated capacity?
• What is the proper pitch for a horizontal hot gas line in a refrigerant system?
• Which type of eye protection is NOT recommended for protecting against flying particles from chipping and grinding?
• In what color combination must a piping system that carries dangerous materials be identified?
• Which of the following materials is NOT suitable for an LP gas line?
• What material is typically used for the construction of ductwork in commercial HVAC systems?
• A manometer filled with oil or water is primarily used to measure what?
• What tool is commonly used to measure airflow in duct systems?
• How often should HVAC systems be inspected and maintained?
• During routine maintenance, what should be checked to ensure the safety of a gas heating unit?
• In a gas heating system, what does a high temperature limit switch do?
• What is the purpose of a thermal expansion valve in refrigeration systems?
• What is the minimum pitch required per foot for a horizontal run of a vent pipe?
• What is the minimum clearance required for a type 1 hood to combustible materials?
• Who has the responsibility of providing hard hats at a jobsite?
• A residential gas heating system experiences extinction pop. Which of the following is generally NOT a cause of this problem?
• How do you determine the right size of a furnace for a building?
• What should a limit control for a group A boiler be wired to interrupt when the contacts open?
• What does "enthalpy" measure in HVAC systems?
• Which of the following could indicate that a compressor has an internal malfunction?
• What is the minimum pitch required for the horizontal run of a vent per foot?
• What situation causes gas pilot flames to be noisy, lifting, and blowing?
• How far must a door be kept from swinging within a vented wall furnace air inlet or outlet?
• What is one benefit of using a variable speed blower in HVAC systems?
• What type of pipe is typically used for gas distribution?
• What is the main function of a heat exchanger in a heating system?
• What is the purpose of a thermostat in an HVAC system?
• How is proper input rating for an appliance determined?
• In plumbing, what is a "trap"?
• What is the minimum clearance required between a manhole cover installed at the top of a boiler and the ceiling above?
• What type of valve may be placed between the boiler safety valve and the atmosphere on the discharge pipe from the valve?
• What minimum work space is required in front of a warm air furnace installed in an attic?
• Which of the following are the two main types of HVAC systems?
• Why is it important to balance air distribution in an HVAC system?
• What is meant by "sensible heat"?
• Where are air vents required in a hydronic piping system?
• How do you calculate the required CFM for an HVAC system?
• What should be considered when placing insulation on pipes?
• What is the main role of a pressure relief valve in a heating system?
• In heating systems, what does "Zoning" refer to?
• What does the term “latent heat” refer to?
• What is the common use for PVC pipe in plumbing systems?
• What is the minimum pitch of a condensate drain connected to a compensating furnace?
• What is the primary purpose of a sump pump?
• What is a pre-fabricated double wall vertical vent from a gas furnace commonly called?
• Pressure loss in a refrigerant piping system is primarily dependent on which factor?
• Why is it important to insulate hot water pipes?
• What must be done to ensure good indoor air quality in HVAC systems?
• What is the minimum operational pressure for a 24 psi pneumatic temperature control system?
• What is a common test for verifying duct leakage?
• What is the purpose of permanent ventilation openings in confined spaces?
• In plumbing, what does the term "drainage" refer to?
• What is the maximum peak sound pressure that employees can safely be exposed to on a jobsite?
• What is the significance of the pressure-temperature (P-T) chart in refrigeration?
• In a refrigeration system, what results from an overheating compressor?
• In HVAC systems, what is often used as a measure of safety in high current applications?
• What is the heat-absorbing capacity per day of a condensing unit rated at 5 tons per hour?
• What system can improve indoor air quality by removing contaminants?
• In a residential space with a volume of 12,000 cubic feet, what is the maximum amount of R-22 allowed?
• In what condition is a heat pump most efficient?
• What is the purpose of a condensate drain in an HVAC system?
• Which testing gas is acceptable for leak testing a gas line?
• Which measurement indicates air pressure in duct systems?
• A permit shall become invalid if not used within how many days of issue?
• In HVAC systems, what is the primary role of a compressor?
• What is the purpose of a flue in a gas appliance?
• Which aspect of a building can significantly affect its energy efficiency?
• What is the relationship between the branch and run in a bull head tee?
• What type of valve is typically used to control the flow of water in HVAC systems?
• All of the following information is required to be on an electric comfort appliance cable EXCEPT?
• What is typically the outcome of applying a load to a transformer?
• What shall be installed at an approved location to shut off fans or blowers in flammable vapor or dust ventilation systems?
• What is a typical function of an HVAC economizer?
• How can the input rating of an appliance be converted into cubic foot of gas?
• What is the difference between a single-stage and multi-stage furnace?
• All of the following may cause a gas pilot to go out during system use EXCEPT?
• What does “air filtration” accomplish in HVAC systems?
• What type of sleeve connects two pipes with internal threads at both ends?
• What is the maximum distance a portable fire extinguisher can be from a hazard?
• How do zoning valves work in a hydronic heating system?
• What type of fitting is generally required for gas connections in a residential setting?
• Which component is essential for preventing flooding in low-lying areas?
• What is the maximum allowable distance between rungs on a ladder?
• What is the key difference between R-22 and R-410A refrigerants?
• What working pressure is required for steel fittings in an LP gas system that will operate at 30 psi?
• What device will prevent a refrigeration compressor from running if suction drops below a predetermined point?
• What does "AFUE" indicate in HVAC systems?
• What is the primary function of a Low Water Cut Out on a low pressure boiler?
• What principle do metal thermo-controls usually operate on?
• What is the typical function of a high probability system located in residential spaces?
• For combustion air drawn from a room with an 8' ceiling and dimensions of 12'X16' with a 12"X16" duct, what is the maximum BTU input allowable?
• What is the primary reason for insulating pipes in plumbing systems?
• What is the effect of using overly long duct runs in a ventilation system?
• Where may gas piping run through in a building?
• What size wire mesh screen should cover combustion air vent openings that terminate on the outside of a building?
• What is the amp draw when a 100-ohm load is applied to 200 volts?
• What is the normal manifold pressure of a gas heating unit?
• In which area is combustion air typically sourced from for gas appliances?
• What is a common consequence of poor duct sealing?
• How do you prevent cross-connection in plumbing systems?
• Which measuring device is best for checking air flow rate from a grille?
• What is a common requirement for venting gas appliances?
• The heat picked up in the evaporator is approximately equal to which of the following?
• During a load calculation, how is the air temperature surrounding a building designated?
• When a technician adds air to an existing gas-fired furnace, which additional loads will require power from the control transformer?
• What does "DRI" stand for in HVAC terminology?
• What does a properly-sized run capacitor do for the compressor in a refrigeration system?
• What is the significance of the pitch in a condensate drain?
• How many inches of water column are equivalent to one pound of pressure?
• What is a consequence of high static pressure in duct systems?
• What is the primary purpose of a thermostat in a heating system?
• What does an increased AFUE rating indicate?
• What could cause a thermostat to not cycle a gas heating unit frequently enough?
• The term "superheat" in HVAC contexts primarily refers to what?
• What are the requirements to install a warm air furnace in an attic?
• What does the term “superheat” refer to in refrigeration?
• What is the primary purpose of a gas meter?
• If a furnace blower motor measures 10 R ohms and draws 5 amps on a 120 volt source, what is the impedance?
• What is the significance of duct insulation in HVAC systems?
• What is the standard clearance for the termination of a gas vent pipe?
• What is the primary function of a thermostat in a heating system?
• Which component in a refrigeration cycle is responsible for compressing the refrigerant?
• What does the term "load" refer to in an electrical context?
• What should be installed to prevent excessive pressure buildup in sections of LP gas pipe that can be isolated?
• Which of the following statements about vent sizing for gas appliances is correct?
• How does a blower door test measure air leakage in a building?
• When assessing the performance of a motor, what does measuring ohms indicate?
• A warm air furnace is to be installed on a building roof that has a 6 in 12 slope. The catwalk requirements for the installation shall have a minimum width of?
• A fuel-burning appliance located in a private garage must have its ignition sources installed by what minimum distance above the floor?
• Which of the following is NOT a feature of electronic control systems?
• The room or space where a boiler will be installed shall have a minimum of how many times the volume of the boiler?
• What can cause a gas burning unit to be turned off by safety control while the pilot is burning EXCEPT?
• For a 400,000 BTU gas furnace in a confined space, what is the minimum allowable free area of each permanent opening for ventilation?
• When more than one heating, cooling, or ventilating system is installed on a roof of a building, each system shall be...
• What is the maximum height above ground for the outside bottom of a horizontal ASME LP gas container?
• What minimum horizontal clearance is required between an operable window and an appliance vent termination?
• Which device prevents a compressor in a refrigeration system from restarting after an overload failure or safety switch cutout?
• Which of the following is NOT a contributor to oil loss from the crankcase of an external drive compressor?
• One pound of pressure is equal to how many inches of water column?
• What is the function of a pressure relief valve?
• How does a PID controller contribute to the performance of heating systems?
• What device is typically used to measure the temperature of the refrigerant in a system?
• What is the standard heat value of gas in BTUs?
• Where should a vent for a fuel gas regulator installed next to an appliance be piped to?
• The volume of a room compared to the volume of a furnace to be installed is based on what maximum ceiling height?
• Which device is responsible for turning off the compressor after it has pumped down?
• What are the conditions of the room air as noted?
• What is the typical composition of refrigerant used in vapor-compression refrigeration systems?
• What is the enthalpy of the supply air given the parameters?
• What is the maximum quantity of flammable liquids that can be stored indoors without an approved storage cabinet?
• What is a key benefit of zoning in HVAC systems?
• Which code is commonly referenced for plumbing installations?
• How does a check valve function in a piping system?
• What type of device is used to control the gas supply to an appliance and is responsive to various conditions?
• When must workers be provided with fall protection?
• What is the typical lifespan of a high-efficiency furnace?
• What safety devices prevent a boiler from operating once the underground side becomes interrupted during an isolation transfer?
• What is typically the cause of a gas leak in heating units?
• What must be ensured when installing appliance connections for gas lines?
• What type of heating load calculations are typically used to size HVAC equipment?
• What should mechanical joints used to connect steel pipe in a fuel-oil supply system be made with?
• Which component is most likely to cause issues with gas flow in a heating system?
• In a warm-air heating system, when will the lockout relay de-energize?
• What is installed in a condensing type gas furnace to lower flue gas temperature and improve heat transfer?
• What is the minimum depth at which underground gas pipes must be buried?