In central air conditioning systems there are two basic methods for delivering air to the conditioned space:
- constant air volume (CAV) systems, and
- variable air volume (VAV) systems
As the name implies, constant volume systems deliver a constant air volume to the conditioned space irrespective of the load. VAV systems, on the other hand, are designed to simultaneously meet a variety of cooling and heating loads in a relatively efficient manner. The system achieves this by varying the distribution of air depending on the cooling or heating loads of each area. The air flow variation allows for adjusting the temperature in a single zone without changing the temperature of air in the whole system, minimizing any instances of overcooling or overheating. This flexibility has made this one of the most popular HVAC systems for large buildings with varying conditioning needs such as office buildings, schools, or apartments.
This 6-hour course covers HVAC air distribution systems with the focus being on Variable Air Volume (VAV) systems. The course is entirely based on US Corps of Engineers Construction Engineering Research Laboratory (USACERL) technical report 99/20, May 1999.
The student must take a multiple-choice quiz consisting of thirty (30) questions at the end of this course to obtain PDH credits.
Specific Knowledge or Skill Obtained
This course teaches the following specific knowledge and skills:
- What is the operational philosophy of variable air volume (VAV) systems?
- What are the differences between pressure dependent, pressure independent and volume limiting VAV boxes?
- What are the various types of fans used in air handling systems including forward curved, backward curved, radial and aerofoil construction?
- What are the different types of cooling coils used in air handling systems and which among face split, vertical split and interwined coils is appropriate for VAV systems?
- What is duct pressure classification and how it is used in selecting appropriate duct sheet thickness?
- How is duct design using equal friction method different from static regain and T-method?
- What are different types of outlets and which parameters govern their selection?
- What is the difference between fan powered, single duct, dual duct and bypass VAV boxes?
- What are different types of VAV controls including direct digital controls?
- What are the common instruments used in acceptance testing and monitoring of VAV systems?
Click on the following link to the PDF document to review the course material before taking the quiz for credit.
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