NCI Article Library

High-Performance HVAC Resources

Induced Draft & Atmospheric Common Venting Interference

When an Induced Draft Appliance (Furnace, Boiler, Water Heater) is "Common Vented" with an Atmospheric Appliance, venting interference can occur. This procedure is the proper method to evaluate this situation and take all precautions to verify safety. Necessary tools...

Adjusting a Ball Valve on Intake of 90% Appliances

Adjusting a Ball Valve on Intake of 90% Appliances by Jim Davis, NCI Senior Instructor In our combustion diagnostics class, we discuss short flues on condensing equipment as causing possible venting problems. We recommend adding a plastic ball valve to the intake of...

How to Use Yellow CO Tags

Last month we brought you a red tag label that you can attach to an appliance when you disable it due to a safety hazard. This month we bring you its cousin, a yellow tag that is to be attached to equipment when you have made modifications or repairs to improve the...

How to Red Tag a Defective System

How to Red Tag a Defective System When following National Comfort Institute Carbon Monoxide and Combustion Efficiency Protocols and procedures there is a chance a dangerous or potentially dangerous condition will be uncovered. If this happens, there are times when...

How to Maintain Your Combustion Analyzer

The primary goal of combustion testing is to take readings you can trust so you can evaluate the operating condition of the combustion appliance. In order to take readings you can trust you have to be sure your combustion analyzer remains in tip-top shape. The...

How to Determine Combustion Air Performance

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 to Adjust Barometric Dampers on Gas-Fired Appliances

The procedure and purpose for adjusting barometric dampers for gas appliances is completely different from the reason you adjust barometric dampers on oil equipment. Let's take a look at each method to get a clearer picture of what we're trying to accomplish. OIL...

Homer Nine and Sons of Beaver, Pennsylvania

May, 2010 NCI Member of the Month

Hard to Pinpoint CO Problem? Narrow It Down

Have you ever noticed a distinct change in CO readings when the blower comes on? Most technicians believe this indicates a cracked heat exchanger. But could it be something else? There are at least three scenarios that could cause this situation on Natural Draft and...