NATE A/C Exam #1. Top Questions & Answers. VERIFIED.

NATE A/C Exam #1. Top Questions & Answers. VERIFIED. 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 - -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. - -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 - -B: Increases An oil separator must be mounted A: Level B: Below the compressor crankcase C: Above the compressor crankcase D: In the suction line - -A: Level Which of the following metering devices controls evaporator pressure? A: Thermostatic expansion valve B: Fixed orifice C: Low side float D: None of these - -D: None of these An automatic expansion valve controls evaporator pressure. The purpose of the external equalizer on a thermostatic expansion valve is A: To equalize evaporator pressure drop with respect to the TEV 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 - -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 - -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 - -A: Refrigerant filter-driers Vacuum pressures are measured in A: Microns B: Millimeters of mercury C: Inches of mercury D: All of the above - -D: All of the above The number 25,400 relates to A: Microns/inch B: Btu/ton C: Cfm/hp D: Cfm/ton - -A: Microns/inch The general rule of thumb for airflow is A: 400 cfm/ton B: 400 cfm/hp C: 6 cfm/sq D: 144 cfm/cu - -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 - -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 - -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 2.25 C: 2 to 3 D: 2.75 to 3.75 - -D: 2.75 to 3.75 Compression rate = discharge pressure (psia) / suction pressure (psia) All else being normal, if a system shows a high lowside superheat with high condenser subcooling, what is most likely the problem? A: Refrigerant overcharge B: Refrigerant undercharge C: A partial refrigerant restriction D: There is probably no problem - -C: A partial refrigerant restriction All else being normal, if a system shows a low lowside superheat with high condenser subcooling, what is most likely the problem? A: Refrigerant overcharge B: Refrigerant undercharge C: A partial restriction D: There is probably no problem - -A: Refrigerant overcharge 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 - -B: Refrigerant undercharge A grille equipped with a damper control is called A: A vane B: A register C: A louver D: A damper - -B: A register A pressure relief valve is A: Direct pressure acting B: Remote pressure activated C: Manually operated D: Reverse pressure acting - -A: Direct pressure acting