The efficiency of an HVAC unit is measured by its potential to circulate the airflow throughout the property or building. Apart from that, an HVAC system should also withstand high temperatures in the hot summer months, to serve its main purpose.
A plenum box plays a major role in helping the HVAC unit maintain its efficacy in airflow and withstanding heat.
Do you know about its implementation benefits?
Can your HVAC system work well without it?
To help understand the necessity of having a plenum box, you must learn about its importance and purpose. So, this article will educate you on the standard definition of an AC plenum along with its benefits and cost to excel your knowledge of HVAC.
What is Plenum in HVAC?
Air distribution and airflow define the root functionality of a heating and air conditioning system. For both hot and cold air, the HVAC units use airflow for making the space comfortable as per the needs. So, to make sure that the airflow is seamless within the HVAC systems, the ductwork must be maintained.
So, where does plenum come in? To ensure that an adequate amount of airflow is achieved within the ductwork, a plenum is used. It is a dedicated section that looks after air distribution throughout the HVAC system.
With plenum boxes, the air is passed into the ductwork and distributed across the system. Large commercial buildings make sure of plenum boxes to enhance the air quality and save money on energy costs. But, even residential homes prefer to use it to control the humidity levels and increase airflow.
Plenum box and plenum are the same, and these terms are used interchangeably in HVAC discussions and works. If one doesn’t maintain the plenum box in periodic intervals, the heated or cooled air will be adversely affected, and houses or properties will become uncomfortable for people to withstand.
As an HVAC contractor, you should advise your customers to consider maintaining their plenum within the system. Tell them that plenum boxes guarantee things such as:
- Eliminating different airflow problems
- Improve air distribution around the home
- Reduced energy costs
- Better air quality
- Increases the life of the HVAC system
Types of HVAC Plenums
HVAC plenums are categorized into four types, out of which supply plenums and return plenums are the standard and most important ones. Both of them are equally important for an HVAC system. The other two types are plenum categories chosen based on preferences. Here is a brief elaboration on all the four types of plenum boxes:
1. Supply plenum
As the name suggests, supply plenum box connects to the supply outlet of your HVAC system. It distributes fresh air around your property and extracts the unclean air from the surroundings. The entire process is executed in a controlled manner, with an integration of the supply system.
To help you understand it better, the HVAC system generates hot or cold air and then passes it onto this plenum. The job of this plenum is to carry this air and distribute it across the system by using the ductwork, to maintain a steady flow all across the property.
A supply plenum is made up of steel, aluminum, or cast iron, which is located at a lowered position in your house.
2. Return plenum
As the air blows into your property, it must return to the system and be re-used and re-distributed across your property. The return plenum takes the filtered and conditioned air back to the system through fans. There are return ducts and vents installed within your property, where professionals connect these plenum boxes.
Experts fit the return plenum along with an air filter. It ensures that the air returning to the system is clean, safe, and free from dust and debris. The return sequence of conditioned air will trigger at least once a day. In simple words, the return plenum recycles the air and converts it into a fresh batch.
3. Ceiling return plenum
Most commercial buildings prefer to use the space above the ceiling for heating and air conditioning systems. The return air grilles will be installed on the ceiling without linking to any air ducts.
Some buildings also have multiple openings right on their ceilings, mostly near windows. In such cases, the owners do not prefer to install a return plenum, as there is no scope of recycling the conditioned air by sending it back to the system.
One of the drawbacks of such a return plenum is that the ceiling openings make the air conditioner noisy as it travels through the openings effortlessly. The space above the ceiling will always be the zone for the negative pressure state. It means that the ceiling plenum will promote infiltration of hot air.
4. Room return plenum
The Air Handling Units (AHUs) use the room as their return air plenum. These units connect the ducts only with the supply outlet. The room has a fresh air opening with a damper for introducing the outside air. As a result, the entire room functions as the return air plenum.
This type of plenum helps in reducing the overall cost of air ducts and will consume less space around the room. The only drawback of such plenum units is that they promote negative pressure. The opening of the AHU rooms promotes return air, but it will still be functioning under a negative state of pressure.
6 Benefits of Plenum in HVAC System
If you are in pursuit of learning the efficacy of plenum, then there is no better way than exploring the benefits of it improving the system functionality:
1. Improve airflow
The components of a plenum, or air distribution box, improve the flow of air within the entire building. It will eventually reduce the humidity levels and create a comfortable environment for a residential or commercial property.
Without proper airflow, you cannot expect your system to comfort the residential or commercial space with heated or cooled air as per your desire. Advise the residents and property owners to seek regular maintenance of the plenum box to maintain the proficiency of airflow.
2. Reducing noise levels
Plenum reduces the noise of HVAC units. Without this component, air distribution will be noisy when it passes through the ducts. Hence, meeting rooms, meditation rooms, and other sensitive areas that need silence will be happy with the benefit of a plenum box.
3. Neutralizes existing air temperature
Suppose you are using an air conditioner system and have set the cooling temperatures in the summer months. The plenum box will ensure that the existing hot air within the room is extracted alongside the supply of cool air into the room.
4. Dirt protection
The ducts must be clean to prevent small dust particles or debris from entering the system. Return plenum links with the air filter to ensure that return air is free from dust and debris before entering air ducts.
Using an air filter is mandatory for commercial spaces where foot traffic is high. Residential homes should also prefer using an air filter and a return plenum to keep the ductwork free from any cloggings in the long run. Ductwork clogging can result in too little airflow.
5. Even distribution of air
The plenum box will help distribute heated and cooled air evenly across the system. Even distribution ensures that the entire property gets heated or cooled down efficiently with a balanced temperature across all rooms.
Supply plenum is the first stop for cool or hot air to get processed and pushed through the ducts. It is the point where plenum evenly distributes the air and sends it to ducts connecting different rooms of the property.
6. Reduced energy costs
The return plenum extracting the conditioned air from the room through return vents is already processed at the required temperature. So, the system implements less load on conditioning the air again unless the thermostat settings change broadly. In this way, the overall energy costs are reduced.
This benefit is highly appreciated by commercial property owners as they have to pay a lot of energy costs if the air conditioning and heating systems are not optimized for energy savings.
How Much Does Plenum in HVAC Cost?
The total average cost per unit for materials and installation of the plenum in HVAC systems starts at $1187. If customers don’t want to compromise on quality, then they can opt for higher variants that might cost up to $1420.
This cost includes the installation expenses and labor efforts to verify the site conditions. Securing the installation to serve the purpose of the plenum box demands challenging efforts. Therefore, the cost is high here.
If there is any issue with the ductwork that connects with the plenum, then the cost would range from $175 to $400 for every duct run. The average cost is around $258/duct or vent run.
Frequently Asked Questions
What is the difference between a duct and a plenum?
Plenum is the air distribution box that attaches to the supply and returns outlets of HVAC equipment. The hot or cold air is passed onto this plenum box, which is spread evenly across the house or office.
The ductwork, on the other hand, is the passage through which the air flows to different rooms of a property. The plenum connects with the ductwork to distribute the air.
Do you need a plenum for HVAC?
It is critical to have a plenum in an HVAC unit. It is because it helps in distributing the air and retrieving it seamlessly to help save energy costs, increase the life of the system, and evenly distribute cold or hot air.
Without it, different rooms of a property will have different comfort levels in terms of air temperature. Apart from that, the load on HVAC units will increase as the conditioned and used air cannot be retrieved and recycled without a return plenum. Therefore, a plenum is crucial for HVAC equipment.
How big should the plenums be?
Single plenums should be a maximum of 24 ft in length, whereas the double plenums should be a maximum of 40 ft in length. If longer lengths are required, then the professionals can consider improving the design of the return and supply plenum boxes.
What are the different types of duct systems?
There are four different types of duct systems which include:
- Flexible ductwork
- Rigid ductwork
- Semi-rigid ductwork
These ducts are in the shape of a tube and are covered with durable and bendable plastic. These ducts are surrounded by an insulating material to maintain the hotness and coolness of the air while it passes through the vents.
What are the risks associated with using an HVAC plenum?
The risks associated with using a plenum involve total failure of the HVAC system. It means that if the plenum gets blocked due to some reason, then the entire system will malfunction and will affect the flow of air. If the air ducts are not installed properly, then the functionality of the plenum will get affected. And eventually, the entire system will have to pay the price. One must call in professional help if there is a diagnosed issue in the plenum.
Apart from that, if there is any low cooling or heating symptom, the plenum will be first checked after initial troubleshooting. In case of an identified problem, repair or replacement might be needed before the system can run properly again.
All the risks can be prevented if the residents or property owners seek proper installation right from setting it up. Routine maintenance is also essential to ensure that wear and tear are identified at the earliest and to prevent high repair costs of the system in the long run.
New residential and commercial properties often prefer installing HVAC units. It is because they are more efficient in maintaining the required temperature within the premises. Qualified and licensed professionals are approached for the job, and as an HVAC contractor, you need to market your services well to be visible to this rising demand.
At the time of installation, you can suggest your clients install plenum onto their HVAC units. If you are new to this field, this article must have helped you learn the benefits of it, which you can also pass on to the clients. Let them know how it will help them with comfort and money savings.
Following that, you can quote your price and take the collective job of installation of HVAC units along with the plenum. Be open to taking up repair and replacement jobs of the plenum for heating and cooling units.