NCI Article Library

High-Performance HVAC Resources

Current Category: Airflow

How to Plot Fan Airflow

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 Determine Combustion Air Performance

by Jim Davis

Combustion air testing is performed using a draft gauge and a CO analyzer. When the draft in the flue of an appliance is low or below -.01" to -.02" W.C. and when CO reading are rising, combustion air problems are present. Carbon Monoxide diagnostics consistently...

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...

How Airflow Affects Heating Efficiency

by National Comfort Institute, Inc.

Airflow is critical to proper heat transfer in heating and air conditioning systems. Most of us know the rule that temperature drop over a cooling coil should be 18 to 22 degrees. If the temperature drop increases, it is evidence that airflow is low. If the...

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...

Gas Pressure Adjustments Done Right

by Jim Davis

Whether starting up new equipment or servicing existing equipment you should never assume that the recommended gas pressure of an appliance will assure safe or adequate operation. Performance cannot be determined until combustion testing has been completed. There are...

Fresh Air for Ventilation and Building Pressurization

by Rob "Doc" Falke

Adding fresh air to a heating or cooling system accomplishes two primary indoor air quality goals: It helps control building pressures and improves indoor air quality by diluting polluted or stale indoor air. Outside air enters the system through a roof or sidewall...

Flue Restrictors-Neutral Pressure Point

by National Comfort Institute, Inc.

Let's say you are working on a furnace, boiler or water heater, and when you take a draft reading the draft goes off scale. This is a good sign you have plenty of combustion air but the excess draft can cause poor fuel-air mixture or increased loss of energy. Using...

Flow Hood Calibration Quick Check

by National Comfort Institute, Inc.

From time to time you may question whether your flow hood is reading accurately. Most of the time, when you're using a quality hood like the TSI 8371, you'll find that even though you might be getting a questionable reading, the problem is not the hood, but the outlet...

Five Airflow Rules You Need to Know

by David Richardson

To understand airflow, you need to have a firm grasp of the rules driving airflow characteristics and behaviors. What you’ll find is many of the most complicated issues you encounter often tie to an airflow problem. Let’s look at five airflow rules that can help you master the airside of your profession.