Category Archives: HVAC Controls

Enthalpy as it relates to free cooling in HVAC

Enthalpy is defined as the amount of internal energy within a system combined with the product of its pressure and volume. When dealing with the term in the HVAC industry, we usually assume that the process is at a constant pressure and, as such, the change in enthalpy is equal to the heat absorbed or released. At its core, the main function of an HVAC system is to transfer heat, which is a form of energy. The first law of thermodynamics, the Law of Conservation of Energy, tells us that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another. From that, we can infer that the only way to cool a space down is to remove the heat energy and transfer it somewhere else, typically outdoors. This is generally accomplished by absorbing heat from an airstream and then distributing this cool air to the area we wish to control; it helps to think of conditioned air like a sponge with the capacity to ‘soak up’ heat. The air, now laden with unwanted heat, is routed back via a Return Air pathway to start the process over again. The newly absorbed heat is ‘wrung out’ and expelled, and the cool air is distributed again in a constant cycle. This ‘wringing out’ process is mainly accomplished by mechanical cooling, such as a compressor, or free cooling provided by an air-side economizer.

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5 Energy Conservation Measures with Quick Returns

The Energy Cost Index (ECI) is the measurement of cost per square foot per year of conditioned space in a facility ($/ft²/year). The average ECI of electricity for an office building in the U.S. is about $1.73/ft²/yr according to the U.S. Energy Information Administration. What are you doing to reduce your ECI?

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CBAS Power User: Greg Gautreaux

CBAS Power User: Greg Gautreaux

Lead Engineer, Stirling Properties

Tell us a little about yourself…

I have been involved in the commercial real estate management industry for forty years in various properties located in Greater New Orleans including the West Bank and Metairie. I am now the Lead Engineer at the Pan American Life Center where I have worked since December 2006.

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CBAS Power User: Alan Cherry

 

Alan CherryAlan Cherry
Plant Engineer, Saddleback College

Tell us a little about yourself…
I have been in the HVAC trade for 34 years now, with my past 22 years at Saddleback College. My first introduction to building automation was a Barber-Colman Network 8000 system featuring a server the size of a small desk and 8” floppy disks for backups. It seems DDC technology has improved a little since then. Continue reading CBAS Power User: Alan Cherry

 

Load Shedding and One Approach in CBAS

 

What is Load Shedding?As I’m sure you know, power companies charge a premium when a certain demand threshold is reached. Load shedding during high electrical demand periods is a good way to lower electrical consumption and avoid paying premium prices for exceeding peak demand limits. Metering or monitoring the load for the building will tell you when that threshold is nearing.

Load shedding will probably not work if the demand follows a bell curve during the day, where the threshold is exceeded for a good portion of the day. In this case, the building needs to find ways of increasing energy efficiency, either by purchasing more efficient equipment, eliminating waste, etc. However, if there is a peak in the demand curve that is exceeded around the same time everyday, load shedding could help. The question is, what can you afford to shut down without making people uncomfortable and angry? Continue reading Load Shedding and One Approach in CBAS

 

Optimal Virtual Metering In Building Automation

 
On March 21, 2018, Computrols Director of Research and Development, Mike Donlon, presented on the topic of “Optimal Virtual Metering In Building Automation” at the Globalcon Conference in Boston, MA. The below information is a transcribed excerpt from his session.


Optimal Virtual Metering - Slide 1 Continue reading Optimal Virtual Metering In Building Automation

 

George’s CBAS Tips, July 2018

 

The Importance of the Probe in BACnet

When setting up 485 communication to a BACnet device like an AHU, it is important that you Probe it. This gets you some important information:

  1. Instance number is a good thing because if you add it to the program screen of the controller, it connects much faster when CBAS is restarted. Instance is usually provided in the Probe file but can sometimes have a different name.
  2. A Probe gets you the list of points that are on the AHU controller. Then you can add them from the Probe file easily by clicking the controller then click Add Points From Probe File.
  3. Perhaps the most important advantage to probing is that it automatically sets a few parameters to be used by CBAS that can improve performance. Note that you can alternatively set these parameters manually.if probing isn’t possible The most useful of these settings are are COV and Read Multiple. COV is Change of Value and if it is available, it sends any changes in value to the host. Read Multiple reads up to 14 points at a time. By default, CBAS only reads one point at a time unless you have Read Multiple set.

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Plug Smart Partnership

 



Computrols Distribution PartnerBuilding automation system manufacturer, Computrols, has added a new distribution partner in Columbus, OH and the Central and South Florida markets. Their new running mate, Plug Smart was formed in 2008 as a customer-centric, comprehensive energy services company.

Beyond their energy efficiency expertise, Plug Smart’s financial team has been very successful at helping to create self-funding opportunities with the Property Assessed Clean Energy (PACE) programs. Continue reading Plug Smart Partnership