Clothes Dryer Systems and Repair
Electric and gas dryer heating systems, drive belts, blower wheels, thermostats, moisture sensors, lint management, and venting requirements.
- Describe the heating systems in electric and gas dryers
- Explain the function of the drive belt, idler pulley, and blower wheel
- Identify the purpose of the high-limit thermostat and moisture sensor
- Explain lint trap function and dryer venting requirements
- Diagnose common dryer faults including long drying times
Leçon 1
Electric and Gas Dryer Heating Systems
Electric Dryer Heating
The type of heating element used in most electric dryers is a nichrome wire resistance element. Nichrome (nickel-chromium alloy) wire is coiled and suspended inside a metal housing. When electricity flows through the high-resistance wire, it heats up to temperatures around 150-180 degrees C (300-350 degrees F), warming the air that passes through the dryer drum.
Gas Dryer Heating
The component in a gas dryer that ignites the burner is the igniter (hot surface igniter or spark ignition). Modern gas dryers use either a glow bar igniter that heats to 1000+ degrees C to ignite the gas, or a spark ignition system. Standing pilot lights are no longer used in modern residential gas dryers.
Electric Dryer
Heat source: Nichrome wire resistance element
Voltage: 240V
Wattage: 4000-5500W
Advantage: Simpler installation
Gas Dryer
Heat source: Gas burner with igniter
Voltage: 120V (controls only)
Gas type: Natural gas or propane
Advantage: Lower operating cost
Heating Element Resistance
The typical resistance range for a good heating element is 10-50 ohms, varying by element rating. Higher-wattage elements have lower resistance (since P = V squared / R). An element reading infinite ohms (open circuit) is burned out. An element reading 0 ohms or very low resistance is shorted.
Element Testing
Always disconnect power before testing. Check resistance between element terminals - a reading of 10-50 ohms indicates a good element. Also check from each terminal to ground - any continuity to ground means the element is grounded and must be replaced.
Electric dryers use a nichrome wire resistance element for heat. Gas dryers use an igniter (hot surface igniter or spark ignition) to light the burner. A good heating element reads 10-50 ohms resistance.