CAV and VAV in HVAC Systems
Twenty to thirty years ago, installing CAV (constant air volume) systems for ventilation and air conditioning in commercial buildings was common. These types of HVAC systems require a large airflow and more energy for heating and cooling, increasing utility costs.
According to the theory, installing a VAV (variable air volume) system will result in significant energy savings.
However, the changes will only be effective if the entire system is adapted. So, let’s compare CAV and VAV HVAC systems with air conditioning contractor kan-service.com in Los Angeles, CA.
In a CAV system, the fan and compressor run at full capacity until the temperature drops to the set point, at which point the compressor turns off.
On/off cycling is ineffective in maintaining a constant room temperature.
CAV systems are small and serve one thermal zone. However, options such as heated CAV, multi-zone CAV, and primary-secondary CAV systems can serve multiple zones and larger buildings.
Two types of CAV systems are commonly used: a terminal reheat system and a mixed air system. A terminal reheat system cools the air in the air handling unit’s zone of rooms. Although it does cool the air, it is inefficient and expensive. A mixed air system has two
air streams. One for the coldest air and one for the hottest air required by the zone’s temperature.
These two air streams are strategically combined to compensate for the room’s load. This system cools the air well, but it does not control humidity.
VAV systems have been designed to meet the heating and cooling needs of different zones of a building. A zone can be a single room or a group of rooms with similar heat gain and heat loss characteristics.
The system effectively dehumidifies the space.
A multi-zone system is also available.
VAV (Variable Air Volume) is one of the most energy-efficient ways to build a ventilation system.
It provides more precise temperature control because the fan speed varies depending on the room temperature. The compressor regulates the flow of refrigerant to maintain a constant air temperature.
The HVAC industry considers VAV systems with independent pressure are the best HVAC system designs. This is the result of an improvement in the terminal block.
Duct Size and Material Matters
Any commercial building owner knows that ductwork is integral to a facility’s operation.
The design, sizing, and ductwork installation ensure that a heating, ventilation, and air conditioning system operates at peak efficiency.
Proper duct sizing is often overlooked in commercial HVAC systems. Duct size and material are important in maintaining a safe and comfortable environment.
The correct duct size and material will help maintain comfortable conditions, improve indoor air quality, minimize energy loss, and lower heating and cooling bills.
How Duct Size Matters
Humidity levels, air temperature, and air pressure in a building all affect the size of ductwork in commercial
spaces.
If the ducts are too large, there is not enough pressure to properly move air to different parts of the building. As a result, the furnace or air conditioner will work much harder than usual to maintain the desired temperature, running much more often and longer than it should.
As you can imagine, this overuse can lead to skyrocketing energy bills.
At the same time, if the ducts are too small, air cannot move adequately to certain building areas. This restriction can increase pressure in the HVAC system, causing premature wear and tear and potentially significant damage.
Ultimately, both sizing issues lead to premature wear, failure, and the inevitable early death of HVAC systems. They also create the need for costly repairs and early replacement. If the ducts are leaky, these problems are further exacerbated.
HVAC professionals use a special formula to determine the correct duct size. This formula takes into account the size of your HVAC unit, friction loss, static pressure,
the area of the rooms in which the air is needed, and
the required airflow rate
The Importance of Duct Material
The most common ducts are usually made of aluminum, stainless steel, or galvanized steel. However, depending on the desired application, they can also be made of fiberglass, flexible plastic, or even fabric. The material does matter and depends on the building and the conditions of the installation site.
Sheet Metal
Rigid sheet metal is the most common type of duct material and is usually made of aluminum and galvanized steel. The interior surface can trap dust and other debris, while the exterior is smooth and easy to clean. This type of duct material has a higher heat loss rate than others.
This is why energy bills are higher.
However, it is the most durable. It is also less likely to develop mold or mildew, and the smooth surface collects less dust than other materials.
Fiberglass
Because fiberglass ducts have a sealed interior lining, they do not need to be cleaned as often as other options. Most fiberglass ducts reduce heat loss due to the additional interior lining. This material also helps reduce the noise the HVAC system produces, making it a common
duct material option, especially in commercial spaces.
Fiberboard
Flat boards of pressed glass fibers are what makeup fiberboard cutting material. These fibers are bonded with resin and have an outer layer of foil to prevent water vapor penetration and leaks. Fiberboard ducts are generally less expensive than sheet metal. They can also reduce noise and resist heat loss and absorption. However, fiberboards are at a higher risk of mold and bacteria growth. Additionally, the rough interior surface can reduce airflow.
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