Beginning Air Testing and Duct Renovation

May 1, 2007
When a contractor learns of air testing and diagnostics, it usually makes perfect sense. If systems don't work as they're supposed to, the inventory of duct renovation is immense. The question is how to get started.

When a contractor learns of air testing and diagnostics, it usually makes perfect sense. If systems don't work as they're supposed to, the inventory of duct renovation is immense. The question is how to get started.

The vision of duct renovation becomes clear when a contractor finally sees there is a part of his industry that he has been missing. Understanding the air side opportunity is the most valuable truth we can inject into a HVAC contracting company to move it toward a positive change in quality and profitability.

This knowledge has the power to transform and revitalize a contracting company. New knowledge is the motivator that brings profits and employees to life.

But remember: Knowledge alone is not power, but the use of knowledge is power. As you review this article, become an active participant in this part of the industry by planning the steps you need to take to become involved in diagnostic selling, and delivering what you have been promising your customers.

Do Systems Work?
Surprisingly, before a contractor can begin down the road of duct renovation, they must accept the fact that many of the systems they currently service and install do not performed as designed, or per the manufacturer's recommendation. This is the toughest part of the whole process.

This industry has good people that are generally very honest and do their best to deliver a good product. But, unless you have tested before, you're probably certain that your systems work perfectly, and that the work that you install needs no diagnostics or repair.

Finding ducting systems with airflow that is 40% below required amounts is the average. After two weeks of measuring airflow, temperatures, and static pressure, you don't even get excited unless a system is more than 50% low on airflow.

Even if you believe your systems are perfect, please read on. In time, you'll know for yourself that a large majority of the systems in your market area are not performing as they should, and 'the other guys' have left you quite an opportunity for service and profit.

Get Knowledge
Past issues of Contracting Business magazine — and the website — are full of information on how to perform testing, balancing, and duct repair. Training is available through industry conferences, seminars, in-house training, and home study courses. There is even information available from several groups on the Internet.

Some basic forms and procedures are needed to get started. A large part of diagnostics is reading and recording information in a format where the results of the data can be evaluated so repair decisions can be made.

Once students learn the principals of air diagnostics, a good practice is to have them participate in training other workers. In our seminars, we give the certified students the challenge to return home and teach others what has been learned. This becomes a valuable educational tool for the entire company.

Test Instruments
Collect needed test instruments. Holding your hand up to a grille and calculating airflow is the most often used explanation offered by the previous contractor. "Yep, you've got air" is not much of a diagnostic procedure.

Capture Hood
The go-to tool in air balancing, and the one used most often, is the capture hood. As many as 30% of contractors own them, but many have not used them in years. The hood covers the grille and funnels the air into its base where the air is measured. Most quality hoods read the CFM on a screen. The average quality hood costs from $2,000 to $3,000.

Our favorite instructions for this tool are: Cover the hole and mash the button. Nearly 80% of the grilles can be read with a capture hood. However, if this is all there were to air balancing and diagnostics, I doubt if our National Balancing Institute would train many HVAC contractors.

Manometers and Magnehelic gauges are devices used to measure pressure. The types are quite varied and cost from $60 to $1800. Manometers measure air pressure in HVAC systems and are essential when interpreting airflow from a capture hood.

Static pressure is read in diagnostics more than any other type of pressure. This reading requires a static pressure tip that is attached to the air stream through a 3/8-in. hole drilled into the ducting. A small rubber or neoprene hose attached the tip to the instrument. The pressure is interpreted and displayed on the tool.

Thermometers to measure temperature and a hygrometer to measure wet bulb are the most common tool use by HVAC service techs today. They measure our product: Heat or cooling. Temperature is a diagnostic value that is too essential to ignore, and is quite easy to measure.

Take temperature rise or drops over a coil or heat exchanger. Measure the comfort that a system delivers from rooms to room. Measure the BTU loss or gain through ducting as it flows through a hot or cold attic.

The bottom line is, the first step is to begin measuring. One of the primary benefits of testing is that you learn so much every time you test. It's fun and motivating. Very soon you'll see that good air diagnostic testing pinpoints the exact problem with the system. You'll be amazed how much knowledge you already possess about fixing airside problems as your testing intuition expands with experience.

Rob "Doc" Falke serves the industry as president of National Comfort Institute a training company specializing in measuring, rating, improving and verifying HVAC system performance. If you're an HVAC contractor or technician interested in receiving a free procedure on temperature diagnostics, contact Doc at [email protected] or call him at 800/633-7058. Go to NCI's website at for free information, technical articles and downloads.

About the Author

Rob 'Doc' Falke | President

Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC-based training company and membership organization. If you're an HVAC contractor or technician  interested in a building pressure measurement procedure, contact Doc at [email protected]  or call him at 800-633-7058. Go to NCI’s website at for free information, articles and downloads.