HVAC Math: Heat Loads, BTU, CFM, Duct Sizing & Refrigeration Basics

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Convert six equipment ratings from BTU/h into tons and kW, convert design temperatures from °F to °C and convert a design temperature difference correctly.
• Work out the net wall area, convert R-values to U-factors, calculate the heat loss of each component of the Lindell house and find which share of the loss goes through the windows.
• Turn air changes per hour into CFM, add the ventilation fan, and calculate the sensible heating load and the sensible plus latent cooling load of the outdoor air.
• Compare the cooling load per square foot of seven rooms, total the design cooling load, convert it to tons, pick the nominal equipment size and highlight the rooms with an unusually high load.
• Set the system airflow from the 400 CFM per ton rule, split it over the rooms by their share of the cooling load, round up the number of supply registers and chart the room airflows.
• Size six duct runs from airflow and design velocity: required area in square inches, round diameter, the next standard size and the actual velocity in the chosen duct.
• Calculate superheat and subcooling from six service readings, compare the right one with the target for each metering device and flag each unit as OK, High or Low.
• Convert EER to COP, estimate the annual cooling energy and cost of five 2.5-ton systems from their SEER, calculate the savings against the existing unit and chart the annual energy.