DIY Network

HVAC: Fan Maintenance From "Trade School" episode DTRS-212

Patrick Chavez

We follow apprentice Patrick Chavez as he gains some of the skills he'll need to become a qualified HVAC technician. HVAC (heating, ventilation, air conditioning) systems control the temperature, humidity, pressure and total air quality in residential, commercial, and industrial buildings. In addition to the installation and repair of HVAC equipment, technicians perform preventive maintenance on these systems to keep them in optimal working condition. We join Patrick as he performs a number of service checks on a large industrial air conditioning unit inside a multi-level office building.

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Fan Maintenance

All air conditioners employ a basic evaporation cycle. A cool refrigerant vapor runs through a compressor, which pressurizes it into a hot vapor. As this hot gas runs through one set of coils, a fan expels the heat away. By removing the heat, the vapor condenses back into a liquid form. Now this liquid runs through an expansion valve, evaporates to become a cold, low-pressure vapor. This cold gas runs through another set of coils. Before the cool refrigerant gas is returned to repeat the cycle, a fan blows air over the cold coils. The chilled air product is distributed throughout a building through a ventilation system.

Multi-story buildings are often too large to rely on refrigerant alone to cool the air. In the building Patrick is working in, a centrifugal chiller employs the evaporation cycle to chill water. The chilled water, now acting as refrigerant on a larger scale, is pumped through pipes to a nearby chamber, where it flows through a large set of coils behind these filter screens. Air is forced over the coils by fans, cooled and distributed through a network of ducts that branch throughout the building. In the meantime, the water circulates back to the chiller and repeats the process.

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