Course: HET 230 - Spring 2015

Lab Assignment

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Unit 3 Lab Assignment

NAME __________________________________  DATE  __________________________

Choose a Furnace or air handler in the lab which has a supply trunk duct and a return drop duct in order to perform the following exercises. You will need a pitot tube, a magnehelic or digital manometer, two lengths of tubing, and Dwyer Air Velocity Calculator. You might have to use a piece of cardboard to block the supply plenum or return drop in order to get a pressure reading.

1. Connect the total pressure port of the pitot tube to the high side (+) of the manometer. Insert the pitot tube into the supply air duct with the open end of the tube pointing into the airflow. Turn on the unit fan and leave it on for the following exercises. Measure and record the total pressure ________inches w.c.

1. Connect the total pressure port of the pitot tube to the low side (-) of the manometer. Insert the pitot tube into the return air duct with the open end of the tube pointing into the airflow. Measure and record the total pressure ________inches w.c.

1. Connect the static pressure port of the pitot tube to the high side (+) of the manometer. Insert the pitot tube into the supply air duct with the open end of the tube pointing into the airflow. Measure and record the static pressure. ________inches w.c.

1. Connect the static pressure port of the pitot tube to the low side (-) of the manometer. Insert the pitot tube into the supply air duct with the open end of the tube pointing into the airflow. Measure and record the static pressure. ________inches w.c.

1. Connect the total pressure port of the pitot tube to the high side (+) of the manometer and the static pressure port to the low side (-) of the manometer. Insert the pitot tube into the supply air duct with the open end of the tube pointing into the airflow. Measure and record the velocity pressure ________inches w.c.

1. Connect the total pressure port of the pitot tube to the high side (+) of the manometer and the static pressure port to the low side (-) of the manometer. Insert the pitot tube into the return air duct with the open end of the tube pointing into the airflow. Measure and record the velocity pressure ________inches w.c.

1. Convert the velocity pressure from #5 above to velocity in feet per minute (FPM) and record here. Show your work using the following formula:

Velocity in ft. per min. = 4005 x   __________________________________

1. What is the area of the supply duct from #5? ______________________

1. Using the area and velocity (FPM) from #7 & #8 above, what is the CFM in the supply duct?

CFM = Area x Velocity ________________________________________________________

1. Realize that this CFM reading is not always accurate because the velocity pressure varies within the duct due to laminar and turbulent airflow.

1. Convert the velocity pressure from #6 above to velocity in feet per minute (FPM) and record here. Show your work using the following formula:

Velocity ft./min. = 4005 x   __________________________________

1. What is the area of the return duct from #6? ______________________

1. Using the area and velocity (FPM) from #10 & #11 above, what is the CFM in the return duct?

CFM = Area x Velocity ________________________________________________________

1. Realize that this CFM reading is not always accurate because the velocity pressure varies within the duct due to laminar and turbulent airflow.

1. Using an Air Velocity Calculator, what is the velocity (FPM) from # 7 above? ________

1. Using an Air Velocity Calculator, what is the velocity (FPM) from # 10 above? _______

1. Turn off the fan and remove your test instruments.

Click on the file below to download the Lab Assignment
- HET 230 Week 3 Lab_Measure Duct Pressures.docx (17.1 KB)