Variable Air Volume(VAV) HVAC Systems

For many years now the variable air volume system has been

considered one of the best types of systems for most types of

commercial, institutional and some types of industrial facilities.

In general the following are the major types of advantages:

1. Savings of Energy: One of the major advantages of the

variable air volume system is the energy savings that result due to

reduced load operation. The system varies the amount of air supplied

to the facility, or a specific area of the facility, to match the actual

space load. Studies have shown that, specifically in office buildings,

the total airflow rate of the supply air fan rarely ever exceeds 80% of

the building's block peak requirement during most of the operating

time. In fact, studies have also shown that for a well diversified

system, the fan system rarely ever exceeds 55% of the fan's rated

capacity for the majority of the time. Figure 1-1 shows that the fan

operates at 52% of its rated capacity for approximately 90% of the

operating time . From this point alone, it is easy to see how much

could be saved in conveying the conditioned air in this manner. Most

other types of air systems must provide a combination of cooling and

heating to provide some form of individual room control. In its very

basic form, the variable volume system does not require both heating

and cooling for individual space control. Instead, it utilizes airflow control.

It can however, depending upon the needs of certain special areas,

be designed with a form of reheat and other types of cooling - heating mixture control.

2. Economizer Cycle Control: During mild weather the variable

volume system can also be designed with an economizer cycle, or

enthalpy cycle, depending on the facility in question.

3. Space Control: The control of space conditions is basically a

simple procedure. Additionally, adding and deleting individual space

control is also a simple process as facilities go through changes over

time.

4. Reduced Initial Cost: When a designer takes advantage of

the diversity which could be part of a variable volume design, the costs of duct work and the space required for equipment could be greatly reduced.

Learn more about other aspects of VAV systems here