Arkansas HVACR NewsMagazine November 2018

S tate, National, Chapter News Tech News

Type B vent pipe, tile lined chimney, or chimney with a flexible liner. Any time multiple appliances are involved, vent connectors are always needed. In addition, the vent section becomes known as the common vent since it serves multiple appliances. And if the common vent needs to have a lower lateral section, that lateral section of the vent becomes known as a manifold. Vent connectors are short runs of pipe, and there are many restrictions on where they can be installed. Vent connectors may not be installed in an enclosed location (such as within an enclosed wall), and they may not pass through walls, floors, ceilings and roofs. These restrictions do not apply to vent connectors made from a vent capable material such as a Type B vent pipe. If the vent and connectors are not properly designed, acidic condensate from the vent gas can easily form on the inside of the vent pipe and cause rusting and pitting. As the corrosion process continues, the vent pipe becomes riddled with holes and ultimately fails. This same condensate can wreak havoc on masonry chimneys as well. Whenever this happens, a chimney could collapse or combustion gas containing carbon monoxide and all the other products of combustion

can leak into occupied areas of the building. Low efficiency gas appliances such as old 78 percent AFUE furnaces rarely have a condensate problem because the combustion gas exits with a relatively high temperature, making condensation difficult to occur. However, many furnaces and heaters have an efficiency above 78% and just below 83% with combustion gases that exit much cooler. These are known as Category 1 gas appliances that are noncondensing, and operate with negative pressure in their vent. These appliances are not designed as condensing type appliances, but they are prone to producing unwanted condensate if they are connected to improperly sized vents and connectors. Because of the many dangers related to acidic condensate, the sizing of vents and connectors is extremely critical for Category 1 type gas appliances. Besides Category 1 appliances, there are Category II, III, and IV appliances. Category II appliances are no longer made, but some are still in operation. These are appliances that operate with a negative vent static pressure and with a vent gas temperature that may cause excessive condensate in the vent. Category III appliances operate with a