The gas furnace in your house is a critically vital equipment and one you rely upon to work reliably, efficiently and quietly. Whether your interest is in understanding more about your current furnace or making a clever choice for a brand new furnace, the issue of gas efficiency is central to any dialogue of residence furnaces.
Conventional vs. Condensing Fuel Furnaces
The applied sciences utilized in compelled air furnaces fall into two broad class sorts:
– Conventional furnaces
– Condensing furnaces
These furnace sorts function very in a different way. In consequence, the furnace heat exchanger fails to collect the utmost quantity of heat from the gas. Conventional furnaces signify an older design that exhaust combustion gases up a chimney flue very quickly before they have an opportunity to cool and before moisture can condense out of them.
With the advent of the condensing furnace, that every one changed. The exhaust gasses are depleted of heat until the water condensate drips out of the furnace’s heat exchanger and the flue gases escape from a plastic PVC pipe as a substitute of a mortar or metallic chimney. Condensing furnaces seize heat even after the combustion exhaust gases have “cooled” and condensed. They do this by using two heat exchangers, one for primary heat exchange and the other to handle the corrosive condensed exhaust gases of water and carbon dioxide (which type carbonic acid).
Furnace Burner and Blower Operation
Within these two broad categories-standard and condensing-furnace types break down even further in line with the operation of the burner and blower. The time period “stage” is used to consult with the operation of the furnace’s burner and blower, and, indirectly, the extent of sophistication of the technology controlling the burner and blower. These stages include:
Single-stage furnaces: This is the least costly, and the label signifies that the burner and blower has one “on” stage.
Two-stage or dual-stage furnaces: This sort has electronic controls that allow the burner flame and burner to be at a excessive and a low setting, depending on the extent of heat required.
Modulating furnaces: This type has digital controls for the burner and blower motor that enable very high quality changes to the burner setting and blower motor velocity, modulating them to keep the temperature of the room very close to the thermostat setting at all times
Furnace Efficiency Ratings
Lastly, a furnace could be categorized in line with AFUE (Anual Fuel Utilization Efficiency) rankings.
Fifty five to seventy two p.c AFUE low-efficiency furnaces: Now out of date for new furnaces, furnaces with this low AFUE rating are still discovered in lots of homes.
78 percent AFUE low-efficiency furnace: Till Jan. 1, 2015, this was the minimum AFUE allowed for new furnaces.
Standard/mid-efficiency gas furnaces: This group consists of furnaces with eighty % (as much as 83 percent) AFUE scores.
High-effectivity gas furnace: These are Vitality Star-certified furnaces with 90 to 98 p.c AFUE ratings.
The AFUE measurement measures the amount of gas converted to heat in the area in proportion to the quantity of fuel that enters the furnace. The upper the AFUE, the more environment friendly the furnace.
Homes at this time are required to have an AFUE rating of a minimum of 78 percent, however furnaces with rankings this low are sometimes found only in manufactured properties. For a furnace to satisfy the Department of Power’s Energy Star program, it should be a excessive-efficiency furnace with an AFUE of 90 p.c or increased.
55 to seventy two p.c AFUE Furnaces (Low Effectivity)
These compelled-air furnaces at the moment are obsolete for brand spanking new development but had been quite common within the 1960s through the 1980s. Their characteristics include:
– Non-compliant AFUE (for brand spanking new furnaces)
Non-digital, standing pilot ignition
– Single-stage furnace
– Single-speed blower
– Natural draft exhaust
– Heavy cast-iron heat exchanger
– Sometimes were oil furnaces transformed to pure gas
78 p.c AFUE Furnaces (Low Efficiency)
In 1987, the Nationwide Appliance Energy Conservation Act set the minimal effectivity level for furnaces at 78 p.c AFUE, which remained in impact until Jan. 1, 2015. Though an improvement over earlier furnaces, these are nonetheless thought of low-effectivity furnaces by as we speak’s standards. Their characteristics embrace:
– 78 % AFUE
– Was typically used in manufactured/mobile homes, space heating functions
– Digital ignition
– Single-stage furnace
– Single-pace blower
– Steel tube heat exchanger
– The pure draft that creates a circulate of combustion gasses.
Eighty to 83 percent AFUE (Standard/Mid-Efficiency)
In 2007, the Department of Vitality proposed a brand new minimal customary of eighty % AFUE, set to enter impact in 2015. Nonetheless, since furnace manufacturers had already met and exceeded this goal effectively earlier than 2015, most consumers now install furnaces that exceed this minimal requirement, many opting for top-efficiency Vitality Star furnaces.
The characteristics of those furnaces:
– 80 % is minimum AFUE allowed for new furnaces as of 01/01/2015
– Some corporations supply models as much as 83 percent AFUE
Digital ignition
– Single- or two-stage design
– Single- or variable-velocity blowers
– Steel tube heat exchanger
– Pure draft creates a movement of combustion gases
90 to 98 percent AFUE (Excessive Effectivity, Vitality Star Permitted)
Launched in 1992, the Energy Star program was a joint endeavor by the U.S. Over time, furnace manufacturers have met pace with the steadily growing efficiency requirements for Energy Star qualification. Shoppers have loved a wide range of tax advantages and rebate opportunities by selecting environment friendly Power Star fashions of furnaces and other appliances. Environmental Safety Company and the U.S. Department of Vitality. It sought to identify and promote energy-efficient appliances aimed toward lowering greenhouse gases.
Presently, Power Star certification for furnaces carries totally different AFUE rankings for southern climates and northern climates. In 2018, the DOE proposed 97 p.c because the minimum AFUE rating to qualify for Energy Star certification, but that call continues to be pending. In 2012, for instance, the Southern Vitality Star qualification for furnaces was set at ninety percent AFUE, and 95 p.c for northern states.
Traits of these excessive-effectivity furnaces embrace:
– 90 % to 98 percent AFUE
– Most carry Power Star scores (ninety % AFUE for South, ninety five percent for North)
– At the moment, 98.7 % AFUE is the best score out there, offered by Rheem
– Condensing furnace design
– Electronic ignition
– Single, two-stage or modulating furnaces
– Variable-velocity blower
– Steel tube main heat exchanger
– Secondary stainless heat exchanger for condensing flue gases
– Sealed combustion chamber
There are practically 800 furnaces obtainable that carry the Power Star approval. Just about every major furnace producer presents Energy Star models.
