Gas and Oil Boilers Key Terms

Understand the terms you'll run into when dealing with gas and oil boilers

By M. Worcester

Gas and oil boilers heat water. Often this hot water is used to heat buildings or run radiators or baseboard heating systems. Boilers can be fueled by home heating oil, natural gas or propane. Gas and oil boiler terminology can include subjects as varied as efficiency ratings to boiler components and parts.

Energy Star rating

Boilers with an Energy Star sticker have an AFUE rating of 85% or higher. Energy Star is a voluntary program overseen by the Environmental Protection Agency (EPA).
Try: Find an explanation of what the Energy Star rating is at Weil-McLain.

AFUE rating

AFUE stands for annual fuel utilization efficiency, a standardized measure of how efficient a boiler is. The higher the number, the better the efficiency.
Try: Check out a glossary of home heating and cooling terms, including AFUE rating, at the American Standard Heating & Air Conditioning website.

Combustion efficiency

Combustion efficiency measures the amount of fuel actually converted to heat. A rating of 100% seems optimal but is actually not achievable, because no system works without some heat loss. This measure isn't the same as the AFUE rating.
Try: Find out more about combustion efficiency and how to measure it at FurnaceCompare.com.

Power venter

A power venter is a way to vent the gases from a furnace or boiler to the outside without the use of a chimney. In many cases, this is a less expensive option since building a chimney is often quite costly. Still, keep in mind that you will need to replace a power venter well before the end of the average lifespan of a well-maintained chimney.
Try: Read a comparison between chimneys and power venters at Warmair.com.

Bleed valves

A bleed valve is used to drain water out of the boiler when performing repair work. You can also use these valves to get trapped air out of the water line.
Try: Find a definition of bleed valves and other components of boilers at Channel4.

Boiler thermostat, aquastat

A boiler thermostat can refer to a wall thermostat that measures and controls air temperature in the area heated by the boiler, or it can refer to a thermostat that measures the actual water temperature within the boiler.
Try: Browse through a glossary of heating-related terms, including boiler thermostat, at De Dietrich.