Thermal Fuse Testing Procedure: A DIY Guide for Dryer Owners

What is a Thermal Fuse?

Types of Thermal Fuses

1. Alloy type:

• Also referred to as thermal connections or bi-metallic thermal fuses.
• These fuses usually involve the bonding of two distinct metals with varying rates of thermal expansion.
• The metals expand at separate rates when the temperature reaches the fuse's rating, breaking the bond and cutting off the circuit.
• Fuse types of alloy are single-use only and cannot be reset.
• They can be used for various purposes since they are economical and dependable.

2. Organic type:

• Also referred to as PTC thermistors or resettable thermal fuses.
• The organic materials used in these fuses have a rapid temperature increase in electrical resistance.
• The resistance dramatically rises when the temperature approaches the fuse's rating, restricting the amount of current that may flow and safeguarding the circuit.
• Fuse types of the organic kind can be reset once the temperature drops.
• They might not last as long as alloy-type fuses and are more expensive.
• They are appropriate for usage in transformers and motors, for example, if resetting the fuse is required.

What does a Thermal Fuse do?

• It keeps an ongoing eye on the temperature in the vicinity of its position.
• There are two possible responses from the fuse when the temperature rises above a set trigger point:
  • One-time usage (alloy type): The electrical circuit is permanently cut off when the interior structure melts or fractures. This protects a single action.
  • Resettable (Organic type): The circuit is protected by a sharply limited current flow caused by a fast increase in electrical resistance. The circuit can function again when the temperature drops and the resistance returns to normal. This provides several reset options.

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How Does a Thermal Fuse Work?

• Alloy-type: The weaker metal melts and irreversibly breaks the electrical connection.
• Organic-type: Current flow is restricted by the sudden rise in resistance of the organic substance.

• Alloy-type: To stop additional overheating damage, the circuit is permanently cut off.
• Organic-type: To prevent additional temperature rise, the circuit keeps running on a low current.

How to Test a Thermal Fuse?

• Multimeter
• Screwdriver (appropriate size for your dryer)
• Replacement fuse (if needed, matching your original rating)

1. Find the fuse: Consult the handbook or internet resources for your model.
2. Enter the compartment: According to the directions on your dryer, carefully unscrew the panels and take out the screws.
3. Capture images: To make reassembly simpler, record wiring configurations.
4. Cut the wires off: Note the color labeling to ensure proper reattachment.

How to Tell if Thermal Fuse is Bad?

• Physical damage: Look for loose parts, melted plastic, and burn marks. These suggest that the fuse may be compromised due to overloading. But being damage-free does not ensure that it works.
• Triggering: The fuse is most likely triggered if you know the device overheated before malfunctioning.

• One-time usage (Alloy): The fuse is probably blown and needs to be replaced if the gadget is completely unusable and has yet to be tampered with.
• Resettable (Organic): The fuse may be deteriorated and need to be replaced if the device operates erratically trips frequently, or exhibits symptoms of overheating.

How Long Do Thermal Fuses Last?

1. Type of fuse:

• One-time use (Alloy type): When triggered, these fuses are made to be used only once and permanently open the circuit. Since their functioning hinges on a single overheating event that exceeds their trigger point, they don't have a set lifespan.
• Resettable (Organic type): You can reset and reuse these fuses multiple times. But with every trigger, they deteriorate and eventually lose their potency. Generally speaking, their lifespan varies from 1000 to 10,000 cycles based on the particular type and quality.

2. Usage and environmental factors:

• Frequency of triggering: Even for resettable varieties, a fuse degrades more quickly the more times it activates. A thermal fuse should ideally only trip in extreme cases of overheating.
• Operating temperature: A fuse's degradation can be sped up by continuously subjecting it to high temperatures, even below its trigger point.
• Environmental factors: A thermal fuse's lifespan may also be impacted by exposure to chemicals, vibration, moisture, or dust.

Conclusion