NCI Article Library

High-Performance HVAC Resources

Current Category: Measurements

How to Use Air Density Correction Factors

Air density correction factors have been a part of our air balancing curriculum since the early 1990's. NCI published a small table years ago and encouraged you to make corrections for air density when measuring airflow at higher altitudes. But the accuracy you are...

How to Select Your First Water Balancing Gauge

by National Comfort Institute, Inc.

When it's time to take your first try at measuring the performance of a hydronic system, you might want to begin with some starter instruments. A hydro- manometer like the big boys use normally costs over $3000.00 each. Although well worth it, you may not want to part...

How to Plot Fan Airflow

by Rob "Doc" Falke

How to Plot Fan Airflow by Rob Falke To be well prepared for this new level of diagnostics, begin collecting copies of the fan data found in most installation instructions for the equipment your company installs and services. The most important diagnostic truth about...

How to Measure Commercial System Efficiency

by Rob "Doc" Falke

How to Measure Commercial System Efficiency by Rob "Doc" Falke, President, National Comfort Institute It’s just not fair. Some contractors have a distinct advantage in the marketplace over their competitors; they ruthlessly and knowingly measure the live operating...

How Does Air Balancing Save Energy?

by Rob "Doc" Falke

How Does Air Balancing Save Energy? by Rob "Doc" Falke, President, NCI Air balancing is a relatively small specialty profession with less than 3,000 commercial supervisors certified by four major organizations. There are fewer than 7,000 residential balancing...

Honest Abe Wouldn’t Guess: He’d Measure

by Andrea Begany-Garsed

Honest Abe Wouldn't Guess: He'd Measure by David Holt The measure of a great country are the people who lead it. Each February, the United States of America celebrates the birth of our greatest -- the 16th President of the United States -- Abraham "Honest Abe" Lincoln...

Heat Strip BTU and Performance

by National Comfort Institute, Inc.

Since the cold has set in we have received many calls and e-mails on PerformanceTalk from contractors and technicians wresting with electric heat systems. The two main topics discussed are: How to determine and rate electric heater performance and how to figure the...

Heat Pumps Can Handle More Filter Pressure Drop?

by Rob "Doc" Falke

It's true: heat pump air handlers can normally afford more filter pressure drop than furnaces with the same fan capacity. As filters continue to increase in efficiency, one parallel fact is that usually the pressure drop over the filter also increases as well....

Five Minute Duct BTU Loss/Gain Procedure

by National Comfort Institute, Inc.

We've all heard our customers describe how their air conditioning system works O.K. in the morning, but doesn't deliver enough cooling in the afternoon. We send out a service tech, he services the unit and reports it's working pretty well. End of story, except our...

Five Airflow Rules You Need to Know

by David Richardson

Five Airflow Rules You Need to Know Troubleshooting the airside of an HVAC system can be one of the most frustrating, yet rewarding challenges you'll have in this industry. Airflow is at the core of what we do -- yet it's one of the most misunderstood aspects of an...