Questions and Answers
Low airflow over a residential split system air conditioning evaporator can cause
Which of the following is the correct sequence of work?
As the pressure on a liquid is increased, the vaporization temperature of the liquid
An oil separator must be mounted
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Which of the following metering devices controls evaporator pressure?
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The purpose of the external equalizer on a thermostatic expansion valve is
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The higher the MERV rating of a filter-drier, the
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Zeolite is used with
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Vacuum pressures are measured in
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The number 25,400 relates to
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The general rule of thumb for airflow is
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A double suction riser is used to
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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 residential split system air conditioning unit?
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Study Notes
Low Airflow Issues
- Low airflow over a residential split system air conditioning evaporator can lead to liquid flood-back to the compressor, causing potential damage.
Correct Sequence of Work
- The proper sequence for air conditioning service is: Attach gauge manifold, recover refrigerant, replace filter core, evacuate the system, and finally recharge the system.
Vaporization Temperature
- Increasing pressure on a liquid raises its vaporization temperature, affecting performance and efficiency in cooling systems.
Oil Separator Installation
- An oil separator must be mounted level to ensure proper operation and oil return to the compressor crankcase.
Metering Devices
- An automatic expansion valve, not the listed metering devices, is responsible for controlling evaporator pressure in air conditioning systems.
Purpose of External Equalizer
- The external equalizer on a thermostatic expansion valve equalizes evaporator pressure drop concerning the TEV to maintain system balance.
MERV Ratings
- MERV ratings do not apply to filter-driers. They measure the efficiency of air filters in removing airborne contaminants, with higher ratings indicating better filtration capabilities.
Zeolite Use
- Zeolite is utilized in refrigerant filter-driers for effective moisture absorption within the cooling system.
Measuring Vacuum Pressures
- Vacuum pressures can be measured in microns, millimeters of mercury, and inches of mercury, providing flexibility in measurement standards.
Microns to Inches Relation
- The number 25,400 relates to microns per inch, an important conversion factor in vacuum measurement.
Airflow Rule of Thumb
- A general guideline for airflow is 400 cubic feet per minute (cfm) per ton of cooling capacity in typical comfort air conditioning applications.
Double Suction Riser Function
- A double suction riser is used to improve oil return as system capacity changes, enhancing overall performance and reliability.
Air Temperature Measurements
- Measuring a return air temperature of 80 degrees and a supply air temperature of 55 degrees may indicate low evaporator airflow, suggesting potential system issues.
Normal Compression Ratio
- The typical compression ratio for comfort air conditioning systems ranges from 1 to 2, indicating acceptable operational parameters.
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Description
Test your knowledge with these flashcards designed for the NATE A/C Exam #1. Each card presents crucial concepts related to air conditioning systems, including airflow issues and proper work sequences. Perfect for anyone preparing for the NATE certification.