Elements of a Heating, Ventilation, and Air Conditioning (HVAC System)

  • Ductwork and related components – Ductwork refers to the passageways through which air is moved in, through, and out of a building.  This can include fresh air intakes, supply ducts (bringing air from the air handling unit to the occupied spaces), return ducts (bringing air from the occupied spaces back to the air handling unit), and exhaust ducts (taking air out of the building).  Grilles, registers, and diffusers separate ductwork from occupied spaces.  Ductwork may or may not be insulated.
  • Air handling units – These are the machines which are primarily responsible for conditioning the air for the occupied spaces, and for providing the power to move the air around the system, although some of the accessories noted above may assist them.
  • Coils (evaporator and condenser) – These transfer heat and cooling, aiding in the conditioning of air.  They are typically very delicate and can be very challenging to clean.  Keeping them clean, however, is crucial, because they easily accumulate dust and dirt, and when dirty or clogged, they greatly reduce heat transfer and air flow, making the system work much harder.  
  • Fans – Fans are a part of every air handling unit, but may also be found at other places within an HVAC system.  Clean fans run more efficiently and are more likely to stay balanced.
  • Grills, registers and diffusers – These separate ductwork from occupied spaces.   Dirty grills, registers, and diffusers sometimes provide the first indication that the system needs to be cleaned.
  • Insulation – Ductwork may be insulated on the inside or the outside to maintain the temperature of conditioned air, and/or to cut down on noise.  Insulation inside ductwork may become worn or frayed over time, which may put unwanted particles into the airstream.  Sometimes insulation must be taken out and replaced.
  • Other components – Ducts may contain accessories such as reheat coils, turning vanes, mixing boxes, and VAV (variable air volume) boxes to control temperature or the flow of air.  All of these parts can accumulate dust, dirt, pollen, and debris over time.