Gas-fired furnace efficiency is expressed by means of a unit’s AFUE percentage. Short for annual fuel utilization efficiency, the AFUE rating provides an at-a-glance metric for comparing the creation of different makes and models of capitalism. AFUE represents the proportion of fuel consumed by means of a furnace that in fact contributes to useable heat versus the amount dropped in the combustion process. A normal efficiency furnace has an AFUE of 80 percent or less, while condensing furnaces with an AFUE of 90 percent or above would be considered high-efficiency models.
Condensing Technology
At a standard-efficiency 80 percent chimney, 20 percent of the heat energy contained in the gas is exhausted up the furnace vent. A condensing furnace with an AFUE of 90 percent or above features a secondary heat exchanger to recover that lost energy. Combustion gases are diverted to your condensing phase and heat released as the gases condense to water is pulled by the secondary exchanger. This fosters the furnace AFUE percent and lowers operating costs.
Variable-Speed ECM Blower
Standard furnaces incorporate conventional single-speed, on/off blower motors. These units produce full blower output when decorated and consume about 500 watts of electricity. The abrupt Sliding cycles of a standard compressor cause marked temperature fluctuations in living spaces. Because full-blast air circulation is not required to maintain temperatures after a house is fully warmed, single-speed operation also consumes excess electricity. Instead of constantly cycling off and on, electronically commutated blower motors called ECM units installed at high-efficiency furnaces are programmed to operate at a selection of speeds keyed to the home’s heating load. These blowers run nearly continuously but at varying, lower output to get rid of on/off temperature swings. In turn, they heat the house more consistently. Because ECM technology consumes only about 80 watts, energy savings are substantial compared to conventional blowers.
Multistage Burners
The gas burner in 80 percent binder runs at full output when operating. In moderate climates, total burner output is necessary only on the coldest days. The remainder of the time it’s an energy-waster. A 90 percent chimney incorporates multistage burners that sense the heating demands of the home and automatically default to a lower, energy-conserving output signal when conditions allow. This lowers operating costs, conserves resources and reduces carbon dioxide emissions.
Sealed Combustion
A normal efficiency furnace draws air for the burner flame from the property’s interior. This dries out the normal humidity in household air and contributes to winter dry-air syndromes like scratchy skin, sore throat and static power surges. It could also pose a health hazard from carbon monoxide in case a backdraft condition grows that shoves combustion gases back into living spaces instead of up the exhaust vent. A 90 percent chimney features a combustion chamber that’s completely sealed in the house. Combustion air is drawn through an inlet pipe routed to the outdoors, and gases are exhausted through another pipe. Backdrafting hazards are eliminated and household humidity is maintained in the comfortable range.