soft, raised surface upon cloth, mid-14c., downy plumage, from Anglo-French pyle or Middle Dutch pijl, both from Latin pilus a hair (source of Italian pelo, Old French pel). Phonological evidence rules out transmission of the English word via Old French cognate peil, poil. Meaning nap upon cloth is from 1560s.
Updated 01/08/17. 1  of 06. Gas Furnace Types and Efficiency Ratings BanksPhotos / Getty Images The gas furnace in your home is a critically important appliance and one you depend on to work reliably, efficiently and quietly. 2  of 06. Low Efficiency Furnace: 55% to 72% AFUE (obsolete technology) Characteristics. 3  of 06.
Now, hereâs the difference between standard-efficiency and high-efficiency models. In gas furnaces, there is a component called a heat exchanger. This is where natural or propane gas is converted into heat energy and byproducts produced from the combustion process are vented through the flue system. Well, in a condensing gas furnace, there is more than one heat exchanger. The secondary heat exchanger removes more heat from the combustion gases, which then condense to produce water vapor. Then, cooled flue gas is vented out of the flue system.