Lets Talk Building Ops: Systems Simplified- Air

In this 8th edition of Lets Talk Building Ops, I will attempt to give you a "Cole’s notes" overview of how air moves from outside to your office space, passing through various equipment along the way to your desk. For the super technical folks, feel free to break down anything further in the comments. My goal is to provide a high-level overview suitable for beginners. Be sure to check out the Glossary at the end of the newsletter for an easy reference sheet!

Meet O.O Air (Ontario Outdoor Air)

Hi, I’m ??Air! Come take a ride with me and see how I end up in your workspace. I’m always changing temperature and humidity depending on the season. In the winter, I’m cold and dry; in the summer, I’m hot and moist. Understanding my "mood swings" are essential for keeping tenant comfort optimal in your building.

Entering the Building: Fresh Air Dampers and Main Air Handlers

I usually start my journey by being sucked through some louvers or dampers ("fresh air dampers"). Once I pass those, I’m inside the Main Air Handler Unit (MAU or AHU are common abbreviations). Some units may just pull air in and push it through without "conditioning" it, while others may heat or cool the air—or do both. In some setups, I may even pass through compartment units throughout the building for additional "conditioning."

The Filtration Process: Pre-Filters and Bag/Box Filters

After entering the air handler, the first item to clean me up from outdoor particles is the "Pre-Filter or Primary." This is typically a 1" or 2" filter cloth or pleated filter, which is changed more frequently, sometimes monthly. Following the pre-filter is a "Bag" or "Box" Secondary filter, much deeper than the pre-filter and usually changed based on manufacturers recommendation. Some units measure "Pressure Differentials" before and after both filters to detect the amount of "particles" clogging them, typically measured in Pascals (Pa). If connected to a Building Automation System (BAS), the unit can trigger an alarm when the pressure becomes too high, indicating filter performance issues.

Heat Transfer and Airflow: The Heat Wheel and Coils

The next item I pass through inside the air handler depends on its age. Newer units may have a "heat wheel" or coil that transfers heat from the exhaust to warm me up in the winter, and in the summer, it cools me down. This makes the heating and cooling system work less to reach the desired set point. After that, I get my big push into the building's ductwork via the main fan. I might then pass through heating and cooling components (coils or burners). In winter, I may even get a little steam to boost my humidity before heading into the ductwork.

Distributing Air: Ductwork, Compartment Units, and Diffusers

As I travel down the main duct, I may be sent to a "compartment unit" for further heating, cooling, and another push by a fan. I then flow through specific-sized ducts that spread across the floor and out of diffusers. Diffusers are usually those white squares in the ceiling, or strips near lights or windows, or in newer buildings, the grey circles in the floor. And voilà—I’m in your space!

Return Journey: Recycling and Exhaust

From here, I’m inhaled and exhaled by people, and then sucked back up into the ceiling space. Sometimes, I’m recycled through a heat pump or Variable Air Volume (VAV) box to filter particles while also being heated or cooled to reach the thermostat's desired temperature. The other part of me is drawn back into the main air handler to be exhausted out of the building. But, as I mentioned earlier, some newer buildings don’t let me leave without extracting any remaining heat or cool through a heat wheel before I finally exit.

Variations in Air Handling: Rooftop Units (RTU) and Different Building Types

The systems I described above are usually found in commercial office spaces, typically in high-rise buildings. For industrial, retail, and some commercial office spaces, Rooftop Units (RTU) handle heating and cooling. The principles are similar, though on a smaller scale. RTUs heat using a heat exchanger (with tubes and burners) and cool with a compressor and condensing coil (much like your home AC). These units are usually serviced quarterly to change filters and check belts and functionality.

Air Handling Types and System Configurations

Air handling setups can vary significantly. Some systems bring fresh air into the building and heat or cool it on each floor through compartment units. Others condition the air before sending it to the space. Larger buildings might have multiple fans, AHUs, and plenums serving as ductwork, with compartment units scattered throughout.

Understanding the Basics for Property Management Success

You don’t need to be an expert, but grasping the essential principles of how these systems work will greatly benefit you in property management. There’s a difference between replacing a fan motor in an RTU compared to an AHU. Sizing matters; understand why, and you’ll be just fine.

Glossary

1. Mood swings: Variations in temperature and humidity.
2. Fresh air dampers: Devices that regulate the amount of outdoor air entering the system.
3. Conditioning: Heating, cooling, or adjusting air humidity.
4. Pre-Filter: A filter that captures large particles before they reach the main filter.
5. Bag or Box filter: A deeper, more efficient filter that captures finer particles.
6. Pressure Differentials: The difference in air pressure measured before and after filters.
7. Pascals (Pa): A unit of pressure used to measure how dirty filters are.
8. BAS (Building Automation System): A centralized system that controls and monitors building operations.
9. Heat wheel: A device that transfers heat between incoming and outgoing air to reduce heating or cooling load.
10. Compartment unit: A secondary air handling unit that conditions air for a specific area.
11. Diffuser: An outlet that distributes air into the room.
12. Heat pump: A device that heats or cools air by transferring heat.
13. VAV box (Variable Air Volume box): A component that adjusts airflow to maintain a set temperature.
14. RTU (Rooftop Unit): An air handling unit located on the roof, commonly used for smaller buildings.
15. Heat exchanger: A device that transfers heat from one medium to another.
16. Plenum: A space in which air can be circulated, often used as a part of HVAC ductwork.

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