Arkansas HVACR NewsMagazine April 2018

furnace must have combustion air. They also know that encapsulating a crawl or attic space shuts off required combustion air. Before we go further, I suppose we should consider what happens when combustion air is reduced and the furnace is starved for air. After visiting with some of the most experienced people in our industry and the Eighth Edition, Refrigeration and Air Conditioning Technology by Tomczyk, Silberstein, Whitman, and Johnson, I came up with this answer. When a furnace is starved of air (oxygen), the flame begins to die back because it lacks sufficient oxygen. For a gas furnace to burn properly it needs 2 ft 3 oxygen per 1 ft 3 natural gas. Since air is about 21% oxygen, it actually takes 10 ft 3 air per 1 ft 3 natural gas for perfect combustion. In perfect combustion, natural gas is only about 9% of the mixture. There is a range but for the purposes of this conversation we’ll use 9%. When the unit is starved of air and the gas mixture reaches 15%, it won’t burn. As the mixture reaches 15% it will produce carbon monoxide and soot. The mixture is too rich. It should be noted that in normal combustion and ventilation the natural gas to air ratio is more normally 1 to 16. As you can see, air is super important to the proper operation of a furnace. We have established 1. the need for proper combustion air; 2. encapsulating a space where a furnace is located greatly

Governor’s Mansion

Carbon Monoxide? Natural Gas? Everyone Makes Mistakes

Ignorance, Carelessness

It Doesn’t Matter

Our Association has been promoting the need for licensing and continuing education for years. I won’t bore you with the history but a recent event reinforces the fact that the HVACR industry serves the public with products and services that relate to health and safety of the public. In this case, the “public” was the Governor. As part of a remodel, a new 80% gas furnace was installed in the crawl space and the crawl space was encapsulated. The crawl space was encapsulated to defend against a rat and mice problem. (This is important to note because the decision to encapsulate was not made with regard for energy efficiency and stopping cold winter air or humid summer air. Had it been, perhaps the relationship between the furnace and stopping air flow would have been considered.) Anyone in the HVACR industry that is keeping up with code and building practices knows that a