012 Mechanical Engineering Terms for Dummies

012-post-mechanical-termsDo you think we should change out the VAV boxes?” Ray asked Chad.

Well, since the AHU is on its last leg, maybe we should spend the money there instead.”

Don’t forget, we need to keep the ACH the same,” piped in the Environmental Health and Safety guy.

I watched as the subject matter experts (SME) served mechanical engineering acronyms back and forth like a tennis ball at the French Open.  At some point, they all looked at me and I smiled knowingly and nodded but I really had no idea what they were talking about.

Since last fall, when this conversation occured, I’ve learned the mechanical engineering (ME) language just enough to carry on short conversations, but I still can’t speak it fluently. In this blog post, I’ll share my ME terms cheat sheet with you. Please note, after the definition of each term I’ve included a link to Wikipedia for more in-depth reading.

  1. ACH– Air Changes per Hour is a measure of the air flow added to or removed from a space (normally a room) divided by the volume of the space. Wikipedia ACH
  2. AHU– Air Handler Unit is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning system. Wikipedia AHU
  3. BAS– Building Automation System is automatic centralized control of a building’s heating, ventilation and air conditioning, lighting and other systems through a Building Management System or Building Automation System (BAS). Wikipedia BAS
  4. CAV– Constant Air Volume is a type of heating, ventilating, and air-conditioning system. In a simple CAV system, the supply air flow rate is constant, but the supply air temperature is varied to meet the thermal loads of a space. Wikipedia CAV
  5. Coil– is a type of heat exchanger for air conditioning of buildings. This class of heat exchangers is commonly called air coils, or just coils due to their often-serpentine internal tubing.  Wikipedia Coils
  6. DDC– Direct Digital Controls is the automated control of a condition or process by a computer. Wikipedia DDC
  7. HVAC– Heating Ventilation and Air Conditioning provides thermal comfort and acceptable indoor air quality for buildings. Wikipedia HVAC
  8. Pneumatic Controls are non-digital HVAC controls. Wikipedia Controls
  9. VAV– Variable Air Volume is a type of HVAC system. Unlike CAV systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature. Wikipedia VAV
  10. VFD– Variable Frequency Drive is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage. Wikipedia VFD
  11. Campus chilled water and steam are produced at central locations on campus and distributed to buildings across campus. Campus Utility Systems

This list of terms is not all inclusive, but they are the ones that I hear most frequently.  If you know of any terms that all project managers should be aware of, please post in the comments below.

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