Psychrometrics and Air Distribution
Moist air, loads and air distribution for HVAC-R technicians, followed through a third-year apprentice in Louisville: humidity ratio, dew point, wet bulb and enthalpy; the psychrometric chart and elevation; coil, mixing and humidifier processes; comfort under ASHRAE 55 and winter humidity limits; heating and cooling loads with Manual J; static pressure, fan curves and the fan laws; pitot traverses, flow hoods and balancing; equal friction duct sizing with Manual D methods and leakage testing; outlets, throw and return paths; ventilation under the IRC and ASHRAE 62.2, HRVs, ERVs and MERV filters; and air-side commissioning of a house and a dental clinic.
RAC-330 12 lessons · 3 h 37 min ▶ Video lessons coming soon
Offered by HSM University · HVAC-R
This is the American version of this course. See the Canadian version.
What you'll learn
- Define and calculate the properties of moist air, including humidity ratio, relative humidity, dew point, wet bulb, enthalpy and specific volume, and use them to explain condensation on cold surfaces
- Plot and read state points on the psychrometric chart from field readings, use the chart for condensation, coil and mixing checks, and correct for elevation
- Analyze sensible heating and cooling, cooling and dehumidifying, mixing, humidification and reheat on the chart, using sensible heat ratio, apparatus dew point and bypass factor
- Evaluate thermal comfort from air and radiant temperature, air speed, humidity, activity and clothing using ASHRAE 55 methods, and set humidity targets that protect health and the building
- Calculate a design heating load from envelope conduction, below-grade losses and air leakage, using design temperatures and the methods of ACCA Manual J
- Calculate a cooling load with sensible and latent parts from envelope, solar, internal and outdoor air gains, and use it to judge equipment size and dehumidification
- Explain static, velocity and total pressure, fan curves, system curves and the fan laws, and diagnose duct restrictions from total external static pressure readings
- Measure airflow by pitot traverse, flow hood, anemometer, blower table and temperature rise, and balance outlets by the proportional method
- Size residential duct systems by the equal friction method from room airflows, available static pressure and total effective length, and seal and test ducts for leakage
- Select and place supply outlets and returns using throw, spread and the Coanda effect, provide return paths for closed rooms, and describe zoning approaches
- Determine ventilation rates for houses and commercial buildings, select and balance HRVs and ERVs, choose filters by MERV rating, and use CO2 as an indicator of ventilation
- Commission the air side of residential and light commercial systems, verifying airflow, static pressure, ventilation, comfort and humidity, and document the results
Course content
12 lessons · 3 h 37 min total · final exam
- 1 Moist air and its properties 23 min · quiz
- 2 Reading and using the psychrometric chart 17 min · quiz
- 3 Air conditioning processes on the chart 20 min · quiz
- 4 Thermal comfort and humidity control 18 min · quiz
- 5 Heating loads 17 min · quiz
- 6 Cooling loads 18 min · quiz
- 7 Airflow fundamentals: pressure, fans and system curves 17 min · quiz
- 8 Airflow measurement and testing 16 min · quiz
- 9 Duct design and sizing 17 min · quiz
- 10 Air distribution: grilles, diffusers and returns 18 min · quiz
- 11 Ventilation, filtration and indoor air quality 19 min · quiz
- 12 Airflow and indoor air quality commissioning: the capstone 17 min · quiz
- E Final exam 20 questions
Requirements
Recommended background. You can start any course at any time.
Description
Moist air, loads and air distribution for HVAC-R technicians, followed through a third-year apprentice in Louisville: humidity ratio, dew point, wet bulb and enthalpy; the psychrometric chart and elevation; coil, mixing and humidifier processes; comfort under ASHRAE 55 and winter humidity limits; heating and cooling loads with Manual J; static pressure, fan curves and the fan laws; pitot traverses, flow hoods and balancing; equal friction duct sizing with Manual D methods and leakage testing; outlets, throw and return paths; ventilation under the IRC and ASHRAE 62.2, HRVs, ERVs and MERV filters; and air-side commissioning of a house and a dental clinic.