BAS Problem Solver Series: Is your building sick?

We all get sick from time to time and have to go to the doctor for one reason or another. We are given remedies in the form of medicine, rehab, rest, etc. There is very seldom a single remedy for whatever illness has taken hold. For example, when you have the Flu you don’t just rest or just take meds, you employ both to maximize your ability to overcome the illness. The same philosophy applies to a building.

Very seldom does one little tweak cure all or get rid of all of the underlying issues. If a building has not been properly maintained it can take a formidable effort to correct the issues that plague a “Sick Building”. The best analogy I can use is if you fall and break your leg you more than likely will have a scrape on your knee as well. We don’t just put a band-aid on the scrape and call it good because there is obviously a major underlying issue beneath the skin’s surface that needs to be addressed.

When diagnosing a sick building it is very important not to jump to conclusions and start throwing band-aids on everything because you can easily create more problems if you employ a misguided solution. All too often a person will find an issue and immediately begin focusing on fixing that issue. What they do not take into consideration is the other issues that may be lurking around the corner that have a tandem impact on building health. It is very important to perform a complete audit of the building before employing any remedy strategies.

The Human Body vs. VAV System: a comparison

If you look at the human body you will notice that it is by far the most synergistic collection of moving parts known to man. There are an infinite amount of processes and checks and balances going on every second. While a building’s HVAC system is a far cry from the complexity of the human body, we can make some very interesting parallels nonetheless. Take for instance the HPT (Hypothalamus, Pituitary and Testes) axis which regulates testosterone and estrogen levels in a man’s body. This can be compared to an air handling system in several ways.

For explanation’s sake let’s start with the Hypothalamus. The Hypothalamus is a part of the brain that, among other tasks, monitors estrogen levels in the blood. Based on the estrogen levels it records, it secretes an enzyme that travels down to the pituitary gland. Based on those levels, the pituitary gland secretes a luteinizing hormone that travels down to the testes. As you can probably guess, based on the amount of LH (Luteinizing Hormone) the testes receive, they then produce a corresponding amount of testosterone and introduce it into the bloodstream where it will either be used or converted back into estrogen and start the whole process over again.

Now let’s make the comparison. A VAV air handling system has a lot of the same functions. Obviously we can’t derive testosterone from an air conditioner, but what we can do, similar to the HPT axis, is create a cohesive exchange between several moving parts resulting in the desired balanced outcome. If we start with the fan in the air conditioner and turn it on, it will begin to pressurize the duct and move air down through the supply and ultimately back through the return to repeat the process. The check for the supply duct is a pressure sensor that measures duct pressure. This pressure will fluctuate based on the damper positions of the downstream VAV’s. As the VAV’s open, the pressure goes down; as they close, the pressure goes up. As the pressure changes in the duct, the sensor sends that feedback to the controller that is controlling the speed of the fan. As the signal from the pressure sensor fluctuates so too does the signal from the controller to the fan. In other words, the sensor provides the check and the controller provides the balance. Sound familiar?

Checks and balances

This ebb and flow of checks and balances is vital to not only the health of our bodies but the health of our buildings as well and when these get out of balance it can be difficult to figure out what exactly is causing the deficiency or where it is originating. While these are very elementary examples, the underlying fundamental processes seldom change. There are undoubtedly many ways to control an air conditioning system and while engineers can argue one strategy over another until the cows come home, the heart of any strategy will always route back to checks and balances. Because of this underlying truth, it is imperative to fully audit or diagnose a building before employing any remedial actions.

To bring everything into perspective, now that we understand the complexity of a control system at a glance, we can’t always focus in on one issue or deficiency when trying to improve the health of a building. Because of the cascading dependence from one device to another, and even one system to another, it is best practice to take into consideration all contributing factors (which sometimes can be easier said than done).

We focus on your needs

So if you are having issues with your building’s HVAC system give us a call at HTS and let us provide you with a full comprehensive understanding of not only what the problem is but what is causing it and what other variables may be involved as well. We have all been to a doctor that runs in, asks a couple questions, and runs out. Wouldn’t you rather have a doctor that takes his time to listen to your concerns and does a thorough examination before prescribing a remedy? We here at HTS think you deserve the extra attention and look forward to helping you improve your buildings health.

-Shane Ray, North Texas BAS Manager