We loan a lot of tools out at the Smart Buildings Center’s Tool Lending Library. Often when the tools come back, they return with a story of success. Recently Jessica Sanborn with Elemental Commissioning borrowed a Vaisala HM 70 Handheld Humidity and Temperature Meter to tune an Enthalpy-based Economizer Controller on an Air-Handling Unit (AHU). Many of you are familiar how Enthalpy-based Economizers work, but for those of you who don’t know and haven’t yet fallen asleep, let us take a minute to explain how these work:

Buildings can generate a lot of heat. The people inside, running of lights, operation of copy machines and computers, and industrial equipment can all generate heat inside of a building and that’s why we need cooling. When cooling a building, there is typically a compressor at work. This could be in an application like a simple air conditioner all the way up to a large and complicated chiller plant. Running these compressors can use a lot of energy and one way of being more energy efficient is to try to minimize the amount of the time the compressor has to run. This can be done with an economizer.

The way an economizer works is whenever the cooling system is trying to cool the building, and the air outside of the building is cooler than the air inside of the building, the economizer system can shut off the compressor and use the cool outside air to cool the building. The only issue with this when the outside air is cool and humid, bringing that outside air into a warm building can make the occupants feel clammy. The solution to this is to incorporate outside air humidity in the equation as to whether to bring outside air in or to utilize the compressor to cool the building. An Enthalpy-based Economizer Controller will make sure that both the air and the humidity outside are low enough to comfortably cool a building.

Now that we have some background, let’s revisit Jessica’s project! Tuning the accuracy of an Enthalpy-based Economizer Controller on an AHU especially near the humid shores of the Puget Sound requires an accurate measurement of temperature and humidity. This can be done with a tool like the Vaisala HM 70. As is often the case, the Building Automation System (BAS) sensor locations were not ideal due to structural and space limitations. Making slight adjustments to the BAS inputs based on the more accurate readings of the actual ambient enthalpy resulted in an increased range of economizer use and a reduction in the controller cycling on and off continuously (which could lead to premature failure). The end results were a considerable energy savings!

Jessica had some choice words to share about her experience with the tool:

If the Vaisala HM70 had not been used to make these slight adjustments, the system still would have satisfied the needs of the space, but the AHU would not have been optimized for energy savings and the humidity.” She also noted, “Having access to this high-end tool has allowed us to commission the system to a higher standard. Thank you Smart Buildings Center!”

The Smart Buildings Center’s Tool Lending Library has over 85 different building diagnostic tools and meters available for loan, come borrow a tool from us and create your next efficency success story.