Author: Jim Davis

CO and Combustion Diagnostics: Cause Versus Symptom

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 the main reason a problem exists.  A symptom is an effect or reaction created by the actual defect/cause. For example, let’s say a piece of equipment is overfired. What type of symptoms could this create? In overfired equipment, the O2 reading is low. When a technician rushes to diagnose a system, he can mistake this for a combustion air problem. In addition, when equipment overfires, it often...

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“Air Free” CO or “As Measured” Carbon Monoxide?

The subject of carbon monoxide (CO) Air Free and As Measured is not new, but still causes confusion due to many conflicting protocols. ANSI standard Z21 lists the maximum allowable CO equipment that can produce CO “Air Free.” The levels according to ANSI Z21 are as follows: 200 ppm Air Free – Unvented appliances and conventional residential water heaters 400 ppm Air Free – Vented heating equipment 800 ppm Air Free – Unvented gas ovens. So, what does this mean? You calculate the CO Air Free value using “As Measured” CO. A dilution factor is then assumed using O2...

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Combustion Air – A Grimm’s Fairy Tale?

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 air, but also highlights the realization that it might be a great idea to control it. So what about providing combustion air? For example, assume your house is located next to a grocery store? Does that mean the house is automatically provided with food? What if we knock two holes in the wall so you can see the grocery store? Now we have...

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