How The Dryer Works - Frigidaire Dryer Servicing

How The Dryer Works

Clothes dryers remove moisture from clothes by pulling
air, either warmed or room temperature, through the
clothes while they are being tumbled by a turning drum.
The moisture from the clothes is exhausted through
the dryer vent system to the outside of the house.
The basic components are:
Drum
Heat Source (Gas or Electric) (See Section 3 for details)
Drive Motor and Blower (See Section 3 for details)
Control Thermistor (See Section 3 for details)
Electronic Control Board (See Section 3 for details)
Airflow
Since the moisture in the clothes is removed by air mov-
ing through the drum, it is important to understand the
complete air flow system.
Airflow Electric Dryers:
Room air enters the dryer through the louvered rear
panel of the dryer. Once inside the dryer cavity the air
is drawn into the heating assembly. In any cycle, other
than Air Fluff, the heating element heats the air as it
passes through. The air is then drawn into the drum
through a duct mounted to the rear inner panel.
The air passes through the drum picking up moisture
and is drawn though the lint filter into the duct work at
the front of dryer. The air enters the fan housing and is
pushed out the exhaust vent to the outside of the house.
Airflow gas dryers:
The air flow in gas dryers is similar to electric dryers
except for the heat source. The air enters the cavity
through the louvered rear panel. The air is pulled across
the gas burner, through the burner chamber and is
ducted to the rear of the drum. The air passes through
the drum picking up moisture and is drawn though the
lint filter into the duct work at the front of dryer. The
air enters the fan housing and is pushed out the exhaust
vent to the outside of the house.
Short Unrestricted Vents
The venting system in the dryer is designed to operate
under some back pressure. This back pressure is
needed to slow the airflow and allow the air to be
heated before it passes through the clothes.
With short direct vent runs; such as you have when the
dryer is installed against an outside wall, use a 2 1/2"
vent cap rather than a 4" vent cap.
Section 1 Basic Information
Airflow problems:
Airflow problems are usually caused by restrictions, leaks
or short unrestricted vents resulting in longer drying
times, hotter dryer surfaces and in extreme cases,
causing the thermal limiter to open on electric dryers.
Restrictions:
Restrictions can occur any place in the airflow system,
but the most common are:
1. Installing the dryer in a small inclosed area; such
as a closet without a louvered door that reduces
the intake air.
2. Fan problems caused by either a slow running
motor, a broken or deformed fan blade or a
deformed fan housing.
3. A lint restriction in the lint screen area. Operator
may not be cleaning the lint screen before using.
4. A restriction in the exhaust system in the house
caused by the design of the vent, such as; the
diameter of the vent pipe being too small, too long,
too many right angles, or a collapsed or lint
restricted vent pipe.
NOTE
Problems caused by the vent pipe in the house are not
covered under the product warranty.
Air leaks:
Two types of air leaks may occur:
1. Air being drawn in around the door opening,
between the drum and front panel, or around the
foam seal between the front duct and blower
housing, replaces some of the air being drawn
through the drum and lowers the efficiency of the
dryer.
NOTE
An air leak that occurs around the door opening or
between the drum and the front panel usually will
cause lint to build up on the inner panel of the door.
2. Air being pushed out around the blower housing
or vent pipe inside the dryer, allows some of the
moisture that has been removed from the clothes
to be recirculated.
1-7