How Do Electric Dryers Work?

Electric dryers have been a staple in modern laundry rooms for decades, providing an efficient way to dry clothes without the need for outdoor clothes lines or cumbersome drying racks.

While dryers may seem straightforward—tumble and heat your clothes until dry—they actually use sophisticated mechanisms to determine when your laundry is perfectly dry.

In this article, we’ll explore the inner workings of two common types of electric dryers: those with an electro-mechanical timer and those with an electronic control board. We’ll dive into how each type manages automatic drying cycles and knows when to stop drying, ensuring your clothes come out just right.

The Basics of How Electric Dryers Work

At their core, all electric dryers function by:

• Generating Heat: A heating element warms the air that flows into the drum.
• Drawing Air Through the Drum: The blower fan draws air through the heating element and into the drum to dry clothes.
• Tumbling Clothes: A motor drives a belt that rotates the drum to tumble garments and dry them evenly. Baffles inside the drum push the clothes around as the drum spins.
• Exhausting Moisture: The blower fan expels the moist air through an exhaust vent system, removing humidity from the drum.

Where dryers differ is in how they monitor the drying process and determine when to end the cycle.

Electro-Mechanical Timer Clothes Dryers

An electro-mechanical timer dryer relies on a simple and durable mechanical system with electrical contacts and a cycling thermostat to control drying cycles. This type of dryer has been in use for decades and remains popular for its affordability and reliability.

How a Dryer Timer Works

The dryer has an electric timer motor connected to a cam gear and rotary dial. You set the desired drying cycle by turning the dial.

When you start the dryer, the electric timer motor rotates the cam that pushes metal contacts to control electric current flow to circuits in the dryer to perform functions such as heating, timer advancement and drive motor operation.

A bi-metal operating thermostat cycles the electric heating element on and off to maintain the right air temperature inside the dryer drum (around 130 degrees).

How the Automatic Drying Cycle Works

In an automatic drying mode, the dryer depends on the operating thermostat to control timer advancement.

• When the air inside the dryer drum is hot enough to trip the operating thermostat and shut off the heat, the dryer timer advances and the timer advancement stops when the air inside the dryer cools down and the electric element turns back on.
• As clothes gets dry, the heating element shuts off more often and the timer advances toward the end of the cycle faster.
• When the timer reaches the end of the drying cycle, the timer shuts off the contact for heating and the dryer uses unheated air to cool down the clothes for about 5 minutes and then the cycle ends and the dryer stops.

A clothes dryer that uses an electro-mechanical dryer is fairly simple to diagnose and repair in most situations. For example, here is a popular DIY troubleshooting video that shows how to diagnose and repair a heating problem in a common dryer with a control timer:

You can gain a thorough understanding of how the control timer system works in a dryer by viewing that video.

If you have a dryer failure that you can’t fix on your own, schedule dryer repair service and we’ll send a Sears Home Services technician to your home to fix the problem for you.

Strengths of Electro-Mechanical Timers

Clothes dryers with control timers offer these benefits:

• Simplicity: Easy to operate and repair.
• Durability: Fewer electronic components mean less susceptibility to failures.
• Dependability: Not susceptible to damage from power surges or brown-outs through electrical supply lines that plague electronic control boards.
• Cost-Effective: These dryers are often more affordable.

Although they have these distinct advantage over electronically-controlled dryers, they typically aren’t as precise at moisture detection in clothes and can sometimes waste energy by continuing the cycle when clothes are completely dry.

Electronic Control Board Dryers

Electronic dryers represent the modern evolution of laundry appliances.

These machines use a control board with temperature and moisture sensors to regulate cycles with impressive accuracy.

How the Dryer Electronic Control System Works

The electronic control board is essentially the brain of the dryer. It uses internal logic and input from sensors to control heat and cycle timing.

Moisture sensors inside the drum play a pivotal role in automatic drying. These sensors measure the electrical conductivity of the laundry load: wet clothes conduct electricity better, while dry clothes reduce conductivity.

Automatic Drying Cycle in an Electronically-Controlled Dryer

The moisture sensor inside the drum play a pivotal role in automatic drying. Here’s how the automatic cycle works:

• Moisture sensor bars measure the electrical conductivity of the laundry load: wet clothes conduct electricity better, while dry clothes reduce conductivity.
• As the clothes dry, the sensor bars detect decreasing moisture levels and send data to the control board.
• The control board adjusts the cycle’s duration to properly dry the clothes without wasting energy.
• When the sensor bars no longer detect moisture in garments, the electronic control shuts of heat and continues to run the dryer to cool down the clothes.
• When the cool down routine ends, the dryer control board signals the end of the cycle.

Strengths of Electronic Control Board Dryers

Electronically controlled dryers off these advantages:

• Energy Efficiency: Optimized cycles reduce energy consumption.
• Precision: Clothes are less likely to overdry, preserving fabric quality.
• Convenience: Many models offer advanced features like wrinkle prevention and steam drying. Smart dryer models can also alert you through a smart device such as your phone or tablet when the cycle ends.

On the downside, electronic dryers can be more expensive upfront and may require professional repairs if the control board or sensors fail.

Maintaining Your Electric Dryer for Optimal Performance

No matter which type of dryer you own, proper maintenance can extend its lifespan and keep it working efficiently. Follow these expert tips to keep your clothes dryer in top shape:

Clean the Lint Filter Screen

Before starting every load, clean the lint filter screen to ensure proper airflow.

Monthly, wash the lint screen using water and a soft-bristle brush to remove fabric softener sheet residue and ensure proper air flow through the dryer. This brief video shows how to wash the lint screen:

Check the Venting System

Keeping the exhaust vent duct system clear of lint and debris is essential to efficient electric dryer performance.

• Regularly inspect and clean the flexible vent hose behind the dryer.
• Clean the exhaust vent duct system going to the outside of your home every six months or as needed to maintain proper exhaust air flow. If needed, you can schedule dryer vent cleaning through Sears Home Services.
• Check the damper for the exhaust vent cover on the outside of your home to make sure that device is opening properly to allow good exhaust air flow.

Failure to keep the exhaust vent duct system clear can result in longer dry times and dryer overheating.

Inspect Moisture Sensors

For dryers that use moisture sensor bars, wipe the sensors periodically to ensure accurate readings.

Deposits on moisture sensor bars can cause the control to stop the automatic drying cycle while clothes are still damp.

Schedule Annual Professional Maintenance

Scheduling professional dryer maintenance and cleaning every year is essential to safe and efficient dryer operation.

Lint and dust can build up inside the dryer cabinet and cause a fire hazard. Having a service technician clean and maintain the dryer will prevent this problem. The technician will open the dryer cabinet and clean out lint and dust during annual preventive maintenance.

The technician will also check and adjust all aspects of electric dryer operation including:

• Checking the entire exhaust system. Lint and debris clogs in the exhaust vent system cause the dryer to take longer to dry clothes. Clothes tumbling in the dryer also can overheat when the exhaust vent system is clogged. The technician will check for leaks, kinks and obstructions.
• Vacuuming inside and around the dryer. The technician will vacuum inside the exhaust vent to remove lint and debris that can cause the dryer to overheat and take longer to dry clothes
• Inspecting the heating system. The technician will check the heating element in an electric dryer or the burner assembly in a gas dryer. The dryer won’t heat efficiently if the burner or element has problems. The technician will check the gas line and connections for leaks, which could lead to a fire.
• Checking the drum, drive system and drum seals. The dryer won’t heat and dry properly if drum seals are worn or damaged. Problems with the drum, drum support rollers, drum belt and drive motor can prevent the drum from rotating to tumble and dry the clothes properly.
• Examining the moisture sensor. The moisture sensor detects dampness in tumbling clothes inside the dryer. If the moisture sensor is coated with deposits (often caused by dryer sheets), the sensor won’t detect moisture and the dryer will stop while clothes are still damp. The technician will clean the sensor if it’s dirty.
• Inspecting the power cord and electrical connections. Damage to the power cord or wiring in the dryer can trip the house circuit breaker for the dryer. A wiring short also can damage internal dryer components such as the electronic control board.
• Measuring dryer operating temperature. The dryer won’t dry the clothes if the burner or control isn’t working properly to heat the air. The technician will measure the temperature of exhaust air to check the heating process.
• Checking controls. Whether your dryer has a timer or an electronic control board, the technician will check control operation. The dryer won’t dry your clothes properly if the control doesn’t work properly.

By maintaining your dryer properly and understanding how the appliance works, you can enjoy fresh, dry laundry without the hassle.

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