NCI Article Library

High-Performance HVAC Resources

How to Redesign an HVAC System – Part I

We've looked, but can't find it. There are mountains of information about how to design a new HVAC system, but nothing much that addresses how to redesign an HVAC system. It would take hundreds of pages to completely detail the process, but let's take a stab at the...

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...

Heat Pumps Can Handle More Filter Pressure Drop?

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....

Getting a Diagnostic Test From a Service Call

Besides the valuable information the reading provides to help resolve the service call issue, it can be a prime lead-in to selling a complete system diagnostic and potential duct renovation work. To provide your customers with air conditioning systems that perform as...

Five Airflow Rules You Need to Know

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.

Finding Heat Pump BTU Output

It's 30 degrees outside and the heat pump is running. Let's say it's a 3 ton unit. What airflow should the equipment deliver through the system and what should the BTU output of that system be under current weather conditions? Last month, NCT included a HeatMaxx...

Find CFM By Measuring Coil Drop on New Installs

There's a fast test for a new installation that is highly accurate and takes just a few minutes. You can get system CFM by measuring pressure drop over a new coil. You simply plot the pressure drop on the coil engineering data sheet and read the airflow passing...

Do You Know How External Filter Racks Impact Total External Static Pressure?

Do You Know How External Filter Racks Impact Total External Static Pressure? A few weeks ago I was asked a question about finding the proper location to obtain the entering static pressure reading on an upflow gas furnace using an external filter rack. This is one of...

Dynamic Air – Las Vegas, NV

Contractor of the month, Tom Johnson of Dynamic Air in Las Vegas, Nevada.

Duct Sizing Made Easy

ACCA manual D and other similar programs are the industry standards for duct sizing. But from hundreds of unofficial polls conducted in our seminars, we have learned that in the "real world" these programs are used for designing less than 1% of the residential and...