combustion
the process by which a fuel is ignited in the presence of oxygen
condensing furnace
a furnace that contains a secondary heat exchanger that extracts latent heat by condensing exhaust gases
heat exchanger
A device that is used to transfer heat from a warm surface to a cooler surface
hot surface igniter
a ceramic devise that glows when an electrical current flows through it. used to ignite the fuel/air mix
induced draft furnace
a furnace in which a motor-driven fan draws air from the surrounding area or from outdoors to support combustion
natural draft furnace
a furnace where the flow of air from around the furnace provides the air to support combustion and venting
standing pilot
found in older furnaces--it produces a small gas flame that remains on all the time.
thermocouple
converts the heat from the pilot flame into a small electrical voltage
flame rectification
a method of providing the existence of a pilot flame by applying an AC current to a flame rod
manometer
an instrument that measures air or gas pressure by the displacement of a column of liquid
infiltration
air that unintentionally and naturally enters a building through doors, windows, and cracks in the structure
multipoise furnace
a furnace that can be configured for upflow, downflow, or horizontal installation
spud
a threaded metal device that screws into the gas manifold. It contains the orifice that meters gas to the burners.
balance point
an outdoor temperature value that represents an exact match o a structure's heat loss with the capacity of a heat pump to produce heat.
sectional boiler
consists of 2 or more similar sections, with each section usually having an equal volume and surface area.
AFUEL
the HVAC industry standard for defining furnace efficiency, expressed as a percentage of the total heat available from a fuel.
atomized
broken into tiny pieces or fragments, such as a liquid being broken into tiny droplets to create a fine spray.
orifice
a precisely drilled hole that controls the flow of gas to the burners.
primary air
air that is pulled into the initial combustion process along with the fuel.
secondary air
air that is added to the mix of fuel and primary air during combustioin