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Energy Basics
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
If all the energy losses described above are taken into account, the overall efficiency of the entire heating system can be determined (including the ductwork), which is often termed the “delivered heating efficiency” or “seasonal efficiency.” If the distribution losses that occur from the piping or ductwork are eliminated, this is defined as the annual fuel utilization efficiency or AFUE. Thus, while AFUE takes into account unburned fuel, the sensible and latent heat losses of combustion gases, excess air losses of non-combusted gases, off-cycling or jacket losses, and the losses of heat through the furnace wall itself, it does not include losses due to distributing the heat around the house that are caused by leaks or uninsulated pipes or ducts. The AFUE is 90 to 97% for high efficiency furnaces and 80 to 90% for medium efficiency furnaces.
Refrigeration Systems and Components
Published in Herbert W. Stanford, Adam F. Spach, Analysis and Design of Heating, Ventilating, and Air-Conditioning Systems, 2019
Herbert W. Stanford, Adam F. Spach
To provide a consistent method of evaluating the energy efficiency of heating and cooling equipment, the U.S. Department of Energy (USDOE), as required by the National ApplianceEnergy Conservation Act, has established test methods and terminology to define “energy conservation efficiency,” as follows: Annual fuel utilization efficiency (AFUE): The measure of seasonal or annual efficiency of a residential heating furnace or boiler. It takes into account the cyclic on/off operation and associated energy losses of the heating unit as it responds to changes in the load. (Note: AFUE is stated as “percent,” and these values must, therefore, be divided by 100 to obtain the decimal value.)Seasonal energy efficiency ratio (SEER): The measure of seasonal or annual efficiency of an electric-drive central air conditioner or air-conditioning heat pump during the cooling season. It takes into account the variations in temperature that can occur within a season and is the average number of Btu’s of cooling delivered for every Watt-hour of electricity used by the air conditioner or heat pump over a cooling season.Heating season performance factor (HSPF): The measure of heating seasonal efficiency of an electric-drive heat pump. The HSPF is the ratio of seasonal heating output in Btu’s [Watt-hours] divided by the seasonal heating power consumption in Watt-hours.
Comfort Heating Systems/Saving Natural Resources
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
As energy costs for natural gas have risen, the need for improving the efficiency of the standard gas furnace has risen. The standard measure of efficiency that compares the amount of heat a furnace delivers to the amount of fuel supplied is the Annual Fuel Utilization Efficiency or AFUE rating. In 1992, the US Department of Energy mandated that all furnaces sold must have a minimum AFUE rating of 78%. Furnaces with an AFUE rating of 78% to 82% are generally titled ‘mid-efficiency’ furnaces. Those furnaces that exceed the 88% rating are considered ‘high-efficiency’ furnaces. This increased efficiency is due to a handful of changes in technology. The first change is the elimination of a pilot light that burns fuel even when there is no demand to an electronic ignition. The second is to draw combustion air from outside the structure, thereby not expelling any air that has already been heated. The most significant change in technology is the ability to extract additional heat from the natural gas so efficiently that the flue gasses condense, or turn vapor into water. It is this ability to condense flue gasses that gives high-efficiency gas furnaces the nickname condensing furnace. These high-efficiency furnaces (see Figure 4-17b) run the spent fuel gasses that would normally be expelled through a chimney of flue through a second heat exchanger. This second heat exchanger extracts additional heat from these gasses that would normally be sent up the flue. This process involving the second extraction leaves flue gasses at such a low temperature that water is condensed and must be drained or pumped away from the system. Because of the low temperature of the flue gasses, venting these gases do not require masonry or triple-wall flues, the gasses can be carried by plastic pipe, thereby making the high-efficiency furnace less expensive to install.
Investigation of occupant-related energy aspects of the National Building Code of Canada: Energy use impact and potential least-cost code-compliant upgrades
Published in Science and Technology for the Built Environment, 2021
Ahmed Abdeen, William O’Brien, Burak Gunay, Guy Newsham, Heather Knudsen
Four code-compliant alternatives were examined for annual fuel utilization efficiency (AFUE) of heating system (gas furnace) under the current occupant-related NBC assumptions versus the newly obtained data (Abdeen et al. 2020) in climate zones 4, 5, 6, 7A and 7B. Such alternatives were excluded for Montreal, and Yellowknife (the represented cities for climate zones 6 and 8, respectively) as most of their households use electricity for their primary heating system.