To stay healthy, you need a balanced diet. Nutritionists worldwide always insist on having a complete meal (a balanced one, for that matter). Why? Your body requires the right amounts of carbohydrates, proteins, and vitamins to stay healthy. Well, enough of playing doctor; let’s get back to our technical world. Just like food, to make the most out of a cooling or heating device, the air must be balanced.
Air balancing is an essential step as far as HVAC commissioning is concerned. Actually, every forced air unit should be balanced during its initial setup – some city/state officials or engineers might demand air balancing before the final approval.
There are other scenarios where air balancing might be required. For instance, when there’s a lack of airflow, cold or warm rooms, and the general inefficiency of an air conditioning unit. Such problems can be rectified by air balancing.
Now, onto our next question: what is air balancing?
Air balancing is the primary process of modifying an existing air conditioning system to ensure that air is evenly distributed in a given space (home/office/industry…etc.). Air balancing makes sure that all zones get enough cool or warm air so that the entire premises is as comfortable as possible.
Let’s take a home, for instance. You want to ensure that every room receives the recommended warm or cold air (From the bedrooms and kitchen to the living and dining areas). You must have heard clients complain about extra warm or cold bedrooms; that could be a problem with air balancing!
Is Air Balancing Important?
No matter how well-maintained or efficient a air conditioning unit or air handler might be, there is always the chance of the air being unbalanced. But the HVAC unit is operating just fine? An air conditioning system banks on a building’s ductwork to distribute cold or warm air. If there’s a problem with the ductwork or the system, the air will be uneven or unbalanced.
The result is usually cold drafts, some rooms never attaining the recommended comfortable temperature, or some areas feeling humid or stuffy than others. Air balancing comes in handy to spot and rectify any issues causing negative air pressure or uneven airflow.
Here are some of the benefits of air balancing.
Improved Indoor Air Quality
Low airflow attracts indoor air contaminants such as mold spores and pollen, leaving certain areas stuffy and stale. A balanced airflow brings in fresher and healthier air, improving air quality in a room/area.
Balanced air ensures even temperatures throughout a given space and takes away chilly drafts. Occupants are not forced to wear sweaters or jackets to access certain chilly areas. Improved comfort also means improved productivity.
Reduces Energy Consumption
When the temperature in a given room is not correct, it is always tempting to lower or crank up the heat. Trying to adjust the temperatures wastes energy. With air balancing, there’s no need to adjust the temperature since every room will be comfortable.
Doors that are hard to open or slam closed
You've probably visited at least one restaurant where the front doors were very hard to open like something was pulling them shut, or a door that when opened will slam itself shut. This is often caused by poor air balancing. When the inside air isn't balanced right, it can literally suck the doors shut in a building. In reverse, too much air being pushed into the space could cause doors to be pushed open by themselves. These are dead giveaways that the inside air isn't balanced correctly.
Air Balancing: A Step by Step Guide
Air balancing can be done in many ways; here are some basic steps to follow.
1. Gather the Right Documents
Before balancing a system, you need to make sure that you have all the proper documents. I know you’re already licensed, but there are some other documents you might want to refer to during the balancing process. Such documents include control documents, duct layouts, equipment specs, and duct design calculations. If you can’t find these documents, insist on having a sketch of the duct system and a record of the nameplates on the air handler.
2. Make Sure the System Is Running Correctly
Once you have the proper documents, the next step is to make sure that the air conditioning unit is running properly. Start it up and check to ensure that it is running close to its designed parameters. The splitter and volume dampers should be open with the correct fan speed engaged.
Don’t forget to take the duct traverse or the static pressure reading to confirm that the pressure and CFM are within the recommended limits. Also, the Delta-T should be within range. Finally, cross-check any other accessories such as the filter to see if they are in the right condition.
3. Take Airflow Reading at Every Supply Outlet
After establishing that the system is operating effectively, it is now time to use your airflow measuring tool to see if the right amount of air reaches every inlet and outlet. While recording these values, keep in mind the Ak (grille) factors. For instance, a flow hood might be ideal for commercial diffusers and a vane anemometer suitable for residential outlets. Check out the manufacturer’s engineering manuals for different Ak factors.
4. Adjust The Dampers Accordingly
After taking the airflow readings, compare them to the manufacturer’s recommended airflows. Damper down (dampers are usually installed in each outlet) the branch outlets with a high airflow till they are within 10% of design. There isn’t the right way to do it; it’s more of a trial and error thing.
5. Take The Final Reading
After adjusting the dampers, it is now time to ensure that all outlet airflows are within 10-percent of the design. Make sure that the dampers are secure, then make the final measurement recording the CFM value. If you have to measure it severally, just do it! If some outlets are not up to the recommended airflow standard, adjust the dampers further till they are within range.
Clients are always looking for comfortable and efficient systems. Balancing is an effective way of assuring your customers that you’ve kept your promise – efficiency and comfort!