The furnace manual reset limit switch is a critical safety component designed to prevent overheating in residential and commercial heating systems. This device automatically shuts off the furnace when temperatures exceed safe operating limits and requires manual intervention to reset, ensuring proper inspection before system reactivation. Below are key sections covering safety, operation, installation, troubleshooting, and maintenance procedures.
Key components: Manual reset button, temperature sensing element, electrical contacts, mounting bracket, wiring terminals.
| Feature | Description |
|---|---|
| Reset Mechanism | Manual push-button reset requiring physical intervention |
| Temperature Range | Typically 90°F to 250°F (32°C to 121°C) |
| Electrical Rating | 120V/240V AC, 15-25 amps depending on model |
| Contact Configuration | Normally closed (opens on temperature exceedance) |
| Mounting | Surface mount with bracket or direct furnace mounting |
| Material | Heat-resistant housing and components |
| Response Time | Rapid thermal response within specified range |
| Safety Certification | UL, CSA approved for furnace applications |
| Durability | Designed for repeated thermal cycling |
| Wiring | Standard screw terminals for easy installation |
Proper installation ensures reliable operation and safety compliance.
WARNING! Disconnect electrical power before installation. Only qualified HVAC technicians should perform installation.
The manual reset limit switch monitors furnace temperature and interrupts power when unsafe conditions occur.
CAUTION! Do not bypass or disable limit switch. Repeated tripping indicates system problems requiring professional service.
Manual reset requires specific steps to ensure safety and proper operation.
Reset Steps: 1. Identify tripped switch (red button typically visible) 2. Allow furnace to cool completely (minimum 30 minutes) 3. Verify no obvious safety hazards present 4. Press reset button firmly until click is heard 5. Restore power and observe furnace startup 6. Monitor operation for repeated tripping
Important: If switch trips repeatedly, do not continue resetting. Contact qualified HVAC technician for system diagnosis.
Proper wiring is essential for safe and reliable operation.
Tip: Follow furnace manufacturer's wiring diagram for specific connection requirements.
Regular testing ensures reliable safety function.
WARNING! Testing should only be performed by qualified personnel with proper safety equipment.
Manual reset design prevents automatic restart after temperature exceedance. Thermal fuse backup provides secondary protection. Tamper-resistant design prevents unauthorized bypass.
Regular maintenance ensures reliable operation. Disconnect power before servicing. Use compressed air to remove dust from sensing element. Inspect for thermal damage or corrosion.
CAUTION! Do not use liquids or abrasive cleaners. Replace if any damage is detected.
UL 353: Standard for Limit Controls. CSA 22.2 No. 205: Signal Equipment. Complies with National Fuel Gas Code requirements. Certified for use in residential and commercial heating systems. Manufactured under ISO 9001 quality standards. For technical support, contact manufacturer or visit www.furnacecomponents.com.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Switch trips repeatedly | Dirty filter, blocked vents, failing blower | Clean/replace filter; check airflow; verify blower operation |
| No reset possible | Internal mechanism failure, excessive temperature | Allow complete cooling; replace switch if still won't reset |
| Furnace won't start | Open limit switch circuit | Reset switch; check wiring continuity |
| Intermittent operation | Loose connections, failing switch | Tighten all connections; replace switch if needed |
| False tripping | Incorrect location, poor sensing | Relocate to proper sensing location; verify calibration |
Replacement: Use identical model number for replacement. Follow manufacturer specifications.
Service: Contact qualified HVAC technician for all repairs and replacements.