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AIR HANDLER / BLOWER UNITS
AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE
BACKDRAFTING HEATING EQUIPMENT
BACKUP HEAT for HEAT PUMPS
BLOWER FAN OPERATION & TESTING
BOOKSTORE - InspectAPedia
CIRCULATOR PUMPS & RELAYS
CONVECTOR HEATERS - HYDRONIC COILS
COOL OFF HEAT, Thermostat Switch
DEFINITION of Heating & Cooling Terms
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC HEAT, DIAGNOSIS, REPAIR
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT
FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FLOODED HEATING EQUIPMENT REPAIR
HEATING LOSS DIAGNOSIS-BOILERS
HEATING LOSS DIAGNOSIS-FURNACES
HEATING SYSTEM INSPECT DIAGNOSE REPAIR
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
MANUALS & PARTS GUIDES - HVAC
NO HEAT - BOILER
NO HEAT - FURNACE
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
PULSE COMBUSTION HEATERS
Reset Switch - Heater Primary Control
Reset Switch Broken - Quick Repair
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
THERMOSTATS, WATER HEATER
THERMOSTATIC EXPANSION VALVES
This article explains AFUE (Annual Fuel Utilization Efficiency) or heating system efficiency ratings and numbers. The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs.
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How is heating boiler efficiency or economy measured? What does boiler AFUE mean?
Here's a very rough example: if the AFUE number for your heater is 80%, that means that for every dollar you spend on heat, twenty cents "goes up the chimney" or is lost in various other ways, and eighty cents of each heating dollar shows up in your occupied space as heat.
Each model of heating boiler or furnace is assigned an AFUE number. Our page top sketch of a high efficiency furnace is provided courtesy of Carson Dunlop Associates.
At left we illustrate a high efficiency gas furnace - expected to have a high AFUE number. Sketch courtesy of Carson Dunlop Associates. Also see this sketch of a high efficiency condensing furnace and this high efficiency pulse combustion heating system.
AFUE is an abbreviation for Annual Fuel Utilization Efficiency. In short, the AFUE tells you, for each dollar you spend on energy for heating by gas, oil, or another fuel, just how much of your dollar shows up inside the occupied space of your building as heat. Higher AFUE is better.
If your boiler or furnace or steam boiler has an AFUE rating of 90, that means that for every dollar you spend on fuel, 90 cents worth of heat is delivered into your building. The remaining 10 cents is lost in inefficiency such as heat that escapes up the chimney along with the products of combustion.
What is the Reliability & Accuracy of Heating System Efficiency Ratings - AFUE?
AFUE is not the whole story of heating cost efficiency. A high-efficiency heating system that has not been cleaned and serviced may be running poorly and wasting money.
In fact, an 85% AFUE heating boiler that has not been cleaned might be running at an efficiency much lower, perhaps 65%.
Furthermore, if your building is drafty or poorly insulated, you may be delivering heat at high efficiency but losing it from the building much faster than necessary.
These articles can help with a more complete approach to saving money on heat:
What are the Current AFUE Requirements for Heating Equipment?
Other Heating System Performance Measurements & Standards
Also see our definition of HSPF, SEER, and other measurements found at SEER RATINGS & OTHER DEFINITIONS
Frequently Asked Questions (FAQs) about the definition of AFUE or heating system efficiency measurements
Questions & answers or comments about AFUE and heating system efficiency ratings, measurement, and improvement
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.