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NATE A/C Exam #1 Questions & 100% Verified
Answers | Latest Update | Already Graded A+
Low airflow over a residential split system air conditioning evaporator can cause A: Liquid flood-back to the compressor B: A decrease in compression ratio C: An increase in suction line superheat D: Oil logging in the evaporator ๐ธ๐ธ๐ธ : A: Liquid flood-back to the compressor Which of the following is the correct sequence of work? A: Attach gauge manifold, recover refrigerant, replace filter core, evacuate the system, recharge the system. B: Recover refrigerant, evacuate the system, replace filter core, recharge the system.
C: Attach gauge manifold, evacuate the system, replace filter core, recover refrigerant, recharge the system. D: Attach gauge manifold, recharge the system, evacuate the system, replace filter core. ๐ธ๐ธ๐ธ : A: Attach gauge manifold, recover refrigerant, replace filter core, evacuate the system, recharge the system. As the pressure on a liquid is increased, the vaporization temperature of the liquid A: Decreases B: Increases C: Remains unchanged D: Varies ๐ธ๐ธ๐ธ : B: Increases An oil separator must be mounted A: Level
B: To equalize the evaporator pressure drop C: To help prevent liquid floodback D: To allow the high side pressure to equalize to the low side when the compressor cycles off ๐ธ๐ธ๐ธ : A: To equalize evaporator pressure drop with respect to the TEV The higher the MERV rating of a filter-drier, the A: More efficient the drier at absorbing moisture B: Less efficient the drier at absorbing moisture C: Smaller the particles the filter can entrap D: MERV does not apply to filter-driers ๐ธ๐ธ๐ธ : D: MERV does not apply to filter-driers Minimum Efficiency Reporting Value - MERV ratings are used to rate the ability of an air conditioning filter to remove dust from the air as it passes through the filter. MERV is a standard used to measure the overall efficiency of a filter. Higher MERV ratings mean
fewer dust particles and other airborne contaminants pass through the filter. Filters with a merv rating of 9 to 12 are used in commercial and industrial applications and will stop particles in the 1 to 3 micron range. These filters are a great choice for home owners who want the best dust control possible. When using filters with Merv 9 ratings and above it is important to clean or replace them when recommended by the manufacturer because they will have a negative effect on air flow when they become dirty. This can lead to performance problems and decreased operating efficiency. The most efficient filters have merv ratings of 13 to 16 and will stop particles as small as .3 microns. These filters are used in hospitals and other super clean environments. Zeolite is used with A: Refrigerant filter-driers B: HEPA filters C: Pipe threads D: Solder ๐ธ๐ธ๐ธ : A: Refrigerant filter-driers Vacuum pressures are measured in
B: 400 cfm/hp C: 6 cfm/sq D: 144 cfm/cu ๐ธ๐ธ๐ธ : A: 400 cfm/ton A double suction riser is used to A: Help improve refrigerant return B: Allow the compressor to pump at a greater capacity C: Decrease suction line resistance D: Improve oil return as system capacity changes ๐ธ๐ธ๐ธ : D: Improve oil return as system capacity changes A service technician measures a return air temperature of 80 degrees and a supply air temperature of 55 degrees. What, if anything, may be wrong with this air residential split system air conditioning unit?
A: Low on refrigerant charge B: Low on evaporator airflow C: Refrigerant overcharge D: There is probably nothing wrong with the system ๐ธ๐ธ๐ธ : B: Low on evaporator airflow The normal compression ratio for a typical comfort air conditioning application should be in the range of A: 1 to 2 B: 1.5 to 2. C: 2 to 3 D: 2.75 to 3. ๐ธ๐ธ๐ธ : D: 2.75 to 3. Compression rate = discharge pressure (psia) / suction pressure (psia)
All else being normal, if a system shows a high lowside superheat with low condenser subcooling, what is most likely the problem? A: Refrigerant overcharge B: Refrigerant undercharge C: A partial restriction D: There is probably no problem ๐ธ๐ธ๐ธ : B: Refrigerant undercharge A grille equipped with a damper control is called A: A vane B: A register C: A louver D: A damper ๐ธ๐ธ๐ธ : B: A register
A pressure relief valve is A: Direct pressure acting B: Remote pressure activated C: Manually operated D: Reverse pressure acting ๐ธ๐ธ๐ธ : A: Direct pressure acting A parallel compressor system in which both the crankcase oil level and the refrigerant gas pressure are equalized is a A: Double pipe crankcase equalizer system B: Single pipe crankcase equalizer system C: External equalizer oil system D: Crankcase hot gas oil equalizer ๐ธ๐ธ๐ธ : A: Double pipe crankcase equalizer system
Which type of copper tubing has the thickest wall? A: Type L B: Type K C: Type M D: Type DWV ๐ธ๐ธ๐ธ : B: Type K Types K, L, M, DWV and Medical Gas tube are designated by ASTM standard sizes, with the actual outside diameter always 1/8-inch larger than the standard size designation. Each type represents a series of sizes with different wall thicknesses. Type K tube has thicker walls than Type L tube, and Type L walls are thicker than Type M, for any given diameter. All inside diameters depend on tube size and wall thickness. Copper tube for air-conditioning and refrigeration field service (ACR) is designated by actual outside diameter. What is the gross weight of a refrigerant cylinder? A: The weight of the cylinder minus the refrigerant
B: The weight of the cylinder plus the weight of the refrigerant C: The weight of cylinder's refrigerant capacity D: The weight of the cylinder and the box around the cylinder ๐ธ๐ธ๐ธ : B: The weight of the cylinder plus the weight of the refrigerant What does an anemometer measure? A: Feet B: Feet per minute C: Cubic feet per minute D: Vacuum pressure in microns ๐ธ๐ธ๐ธ : A: Feet The anemometer only measures feet while the operator uses a stop watch or second hand on a watch. This is a typical "trick" question to watch for The term "induced draft" most likely refers to
A: Rotating vane rotary B: Fixed vane rotary C: Scroll D: Reciprocating ๐ธ๐ธ๐ธ : C: Scroll http://www.ehow.com/how-does_5047455_scroll-compressor-work.html A hot liquid line with a low to normal high side pressure is an indication of A: An overcharged system B: An undercharged system C: Air in the system D: A restricted filterdrier ๐ธ๐ธ๐ธ : B: An undercharged system Air and water are directed counterflow so as to
A: Average the flow rate B: Gain the greatest amount of heat transfer C: Reach the lowest apparatus dew point D: Control the humidity ๐ธ๐ธ๐ธ : B: Gain the greatest amount of heat transfer Which of the following applications is not a mechanical cooling system? A: Cascade system B: Reciprocating compression system C: Evaporative cooling D: Centrifugal compression system ๐ธ๐ธ๐ธ : C: Evaporative cooling A compressor is short cycling. Which of the following would not be the cause?
A: square B: cube C: rate D: inverse ๐ธ๐ธ๐ธ : B: cube BHP2 = BHP1 x ((CFM2/CFM1)cubed) Abnormally low suction pressure can be caused by which of the following? A: Dirty air filter B: Partially restricted filter-drier C: Shortage of refrigerant D: Any or all of these ๐ธ๐ธ๐ธ : D: Any or all of these
Which of the following compressor oil types is generally considered the most compatible with HFC refrigerants? A: POE B: AB C: Mineral D: Vegetable ๐ธ๐ธ๐ธ : A: POE The factor determining the correct quantity of air for each room in a building is A: The calculated heat load for each room B: The size of the room C: The size of the ducts D: The customer's preference ๐ธ๐ธ๐ธ : A: The calculated heat load for each room
