Types of Gas Furnaces
There are two classes of gas furnaces, 80% efficient and 90% efficient. And each class has its own sub-class of gas furnaces.
80% Gas Furnaces
What is a
Single Stage Gas Furnace?
The
typical gas
furnace has only one speed: Full Blast.
It quickly
warms your home to the temperature
you've set and
then shuts off. Single Stage denotes
that when your
thermostat "calls" for the furnace to
come on, all of
the available heat is turned on at
once.
What is a Two Stage Gas
Furnace?
With a two stage gas
furnace, you get
continuous comfort. When your thermostat
"calls" for
heat, only part of all the available
heat is used
(First Stage). After a period of time,
if the
temperature setting at your thermostat
is not
reached, the remainder of available heat
is utilized
(Second Stage). When the furnace is
operating at
first stage, the blower motor runs at a
lower speed
than it does while in the second stage.
Typically,
the two stage gas furnace operates in
first stage 95%
of the time. Two stage heating
eliminates the
frequent starting and stoping common to
conventional
units and uses a lot less energy than
single stage
furnaces.
What is Variable
Speed?
Variable speed refers to
the blower
motor. A variable speed motor varies its
speed
depending upon your homes requirements.
During
continuous fan operation, the blower
operates at 50%
of
cooling air flow so sound is minimized.
Also, a
slower fan speed means more unwanted
dirt and
allergen cling to the
filter.
Major Components of Gas Furnaces
