If you are a homeowner, you know how important it is to keep your furnace in good working condition during the cold winter months. One of the essential components of any furnace is the fan limit switch. In this article, we will explain what the fan limit switch is, how it works, and how to wire it correctly. We will also answer some frequently asked questions about furnace fan limit switches.
What is the Fan Limit Switch?
The fan limit switch is a component of a furnace that controls the fan’s operation. It is a safety feature that prevents the furnace from overheating and causing damage. The fan limit switch is usually located just below the furnace plenum chamber, and it is connected to the blower motor and the thermostat by a series of wires.
The fan limit switch is designed to turn on the blower fan when the air inside the furnace is hot enough. It does this by using a bimetallic strip that expands and contracts with temperature changes. The strip is connected to a switch that activates the fan. When the temperature inside the furnace rises above a certain level, the switch closes, turning on the fan. When the temperature drops, the switch opens, turning off the fan.
How to Wire the Fan Limit Switch
Wiring the fan limit switch correctly is crucial to ensure safe and efficient operation of your furnace. Here are the steps to follow:
- Turn off the power to the furnace.
- Locate the fan limit switch. It is usually located on the front of the furnace, just below the plenum chamber.
- Remove the cover plate from the switch to expose the wiring terminals.
- Identify the wires that are connected to the switch. There will be at least two wires, one going to the blower motor and one going to the thermostat.
- Disconnect the wires from the old switch, making a note of which wire goes where.
- Connect the wires to the new switch in the same order as they were connected to the old switch.
- Replace the cover plate and turn on the power to the furnace.
Make sure to double-check the wiring and test the fan limit switch before running your furnace.
Frequently Asked Questions
1. How do I know if my fan limit switch is faulty?
If your furnace is not heating properly, the fan is running constantly, or you hear strange noises coming from the furnace, it may be a sign that the fan limit switch is faulty. You can test the switch using a multimeter or call a professional HVAC technician to diagnose and fix the problem.
2. What is the ideal temperature setting for the fan limit switch?
The ideal temperature setting for the fan limit switch depends on your furnace’s specifications. Check your furnace’s manual or consult a certified technician to determine the correct temperature setting for your specific model.
3. Can I replace the fan limit switch myself?
While it is possible to replace the fan limit switch yourself, we recommend calling a professional HVAC technician to ensure a safe and proper installation. Improper wiring or installation can lead to serious safety hazards, including fire, electrical shock, or personal injury.
4. How often should I check my fan limit switch?
We recommend checking your fan limit switch at least once a year, ideally before the start of the heating season. Regular maintenance and inspection will help prevent breakdowns and extend the life of your furnace.
5. How can I prolong the life of my fan limit switch?
Regular maintenance and cleaning of your furnace, including changing the air filter and checking the fan limit switch, can help prolong its life. It is also essential to have your furnace inspected and serviced by a professional HVAC technician on a regular basis.
| Term | Definition |
|---|---|
| Bimetallic strip | A strip of two different metals that bends when heated, used in the fan limit switch to activate the fan. |
| Plenum chamber | A sealed compartment in the furnace that distributes air throughout the home. |
| Multimeter | A device used to measure voltage, current, and resistance in electrical circuits. |
| HVAC | Heating, ventilation, and air conditioning. |
