NCI Article Library

High-Performance HVAC Resources

Diagnosing a Long-standing Water Heater Pilot Problem

It appears that certain water heater pilots may have been undersized in the field for the last 15 years or more. For over a decade we have received reports from NCI technicians working on pilot outage problems finding pilot orifices sized for propane pilots on natural...

Dealing With Venting-Related Moisture Issues

Most technicians are familiar with the term Pre-Purge used to define the mechanical operation of a burner fan or draft fan prior to ignition of a burner. The main purpose of pre-purge is to operate the fan or blower to clear the combustion chamber or heat exchanger of...

Dealing With Condensing Furnace Venting Issues

The winter of 2007 delivered several extremely cold blows across the country that was not only good for business, but made evident condensing equipment deficiencies that we don't see too often. Before winter slips away, it's a good time to identify and file away three...

Common Vent Test: Induced Draft and Natural Draft Appliances

When an Induced Draft Appliance (Furnace, Boiler or Water Heater) is "Common Vented" with a Natural Draft Appliance, venting interference can occur. This following procedure outlines the proper method to test and evaluate this situation and helps ensure all...

Commercial Boiler Combustion Testing

Commercial burners may appear to be intimidating and you might feel they're too big to for you to work on. But when you gather the nerve to get your hands on one you'll find they are not that complicated and are quite simple to combustion test and adjust. Commercial...

Combustion Diagnostics Yield High-Margin System Repairs

Those who have implemented Combustion Diagnostics in their service agreements know that technology has given us the ability to uncover mechanical deficiencies with fuel burning appliances like never before. Combustion analysis helps us detect improper fuel input,...

Combustion Air Diagnostics

According to NCI's Protocol, rising CO readings indicate combustion air or venting problems. In either case, flue gases are spilling into the space, requiring immediate attention. By measuring draft you can differentiate between venting and combustion air problems....

Combustion Air – a Grimm Fairy Tale

Combustion Air - a Grimm Fairy Tale by Jim Davis When it comes to combustion air, safety truths created by someone's imagination -- based on little or no factual data whatsoever -- nothing but fairy tales. This article not only addresses the need to provide combustion...

CO and Combustion Diagnostics: Cause Versus Symptom

Jim Davis, Senior Instructor, National Comfort Institute When using the NCI Combustion Diagnostic Reports and Diagnostic Matrix, it is important to recognize the most likely defect/cause of the problem, versus a symptom that it creates. Specifically, a defect/cause is...

CO & Combustion Repair Procedures

Many NCI members have requested that we include repair procedures in our member downloads. October's theme is CO and Combustion testing, so we have included some one-page repair procedures that you'll find helpful this fall while addressing heating system performance....