Carrier Furnace Manual Reset Limit Switch

The Carrier Furnace Manual Reset Limit Switch is a critical safety component designed to protect your heating system from overheating and potential damage. This device monitors furnace temperature and automatically shuts off the burner if temperatures exceed safe operating limits, requiring manual reset once the system has cooled. Below are key sections for safety, operation, troubleshooting, and maintenance procedures.

1. Features and Function 2. Safety Information 3. Location and Identification 4. Reset Procedure 5. Common Causes of Tripping 6. Testing and Inspection 7. Replacement Guidelines 8. Technical Specifications 9. Maintenance Requirements 10. Warranty Information 11. Troubleshooting

Features and Function

The manual reset limit switch provides essential overheating protection for Carrier furnace systems.

Feature	Description
Manual Reset Requirement	Requires physical reset after tripping to ensure safety inspection
Temperature Sensing	Monitors heat exchanger temperature continuously
Safety Shutdown	Automatically cuts power to burner when temperature limits exceeded
Visual Indicator	Red reset button indicates tripped status
Durable Construction	Designed for high-temperature furnace environments
Compatibility	Specific to Carrier furnace models and specifications

Safety Information

Critical safety precautions for limit switch operation and maintenance.

Always turn off power to furnace before inspection or reset attempts.
Allow furnace to cool completely before resetting the switch.
Investigate and resolve the cause of tripping before resetting.
Use only Carrier-approved replacement parts.

WARNING! Repeated resetting without addressing underlying issues can cause furnace damage and create fire hazards. Contact qualified technician if switch trips repeatedly.

Location and Identification

The limit switch is typically located on the furnace plenum or heat exchanger assembly.

Consult your specific Carrier furnace model manual for exact location.
Look for a small device with a red reset button protruding.
Usually mounted near the heat exchanger for accurate temperature monitoring.
May be identified by wiring connected to furnace control board.

NOTE: Location varies by furnace model. Refer to unit-specific documentation.

Reset Procedure

Follow these steps to safely reset the manual limit switch.

Turn off furnace power at the circuit breaker or service switch.
Wait 30 minutes for furnace to cool completely.
Locate the manual reset limit switch (red button visible when tripped).
Press the reset button firmly until it clicks into place.
Restore power to the furnace.
Observe furnace operation for proper function.

CAUTION! If switch trips again immediately, do not continue resetting. Contact professional service.

Common Causes of Tripping

Dirty Air Filter: Restricted airflow causes overheating
Blocked Vents: Obstructed supply or return air ducts
Faulty Blower Motor: Inadequate air circulation
Dirty Heat Exchanger: Reduced heat transfer efficiency
Undersized Ductwork: Insufficient airflow capacity
High Static Pressure: System resistance too high

Testing and Inspection

Regular testing ensures proper limit switch operation.

Visual Inspection: Check for physical damage, corrosion, or loose connections. Functional Test: Monitor switch during furnace operation cycle. Resistance Check: Use multimeter to verify electrical continuity when reset.

Recommended inspection frequency: Annually before heating season.

Replacement Guidelines

Replace limit switch if damaged or malfunctioning.

Turn off all power to furnace.
Disconnect wiring from old limit switch, noting connection positions.
Remove mounting screws and old switch.
Install new Carrier-approved replacement switch.
Reconnect wiring exactly as previously configured.
Restore power and test operation.

Important: Use only exact replacement parts specified for your furnace model.

Technical Specifications

Temperature Rating: Varies by model (typically 200°F range)
Reset Type: Manual push-button reset
Electrical Rating: 120V AC, specific amperage by model
Mounting: Screw mounting to furnace assembly
Wire Connections: Standard spade terminals
Material: High-temperature resistant housing

Maintenance Requirements

Proper maintenance prevents unnecessary limit switch tripping.

Replace air filters monthly during heating season. Keep vents and registers clear of obstructions. Schedule annual professional furnace inspection and cleaning. Ensure blower wheel is clean and operates smoothly.

Maintenance Schedule: Professional service recommended annually.

Warranty Information

Carrier furnaces and components are covered by manufacturer warranty. Limit switch typically covered under parts warranty. Professional installation required for warranty validation. Contact Carrier authorized dealer for specific warranty details and claims.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Switch trips repeatedly	Dirty filter or blocked airflow	Replace filter; clear obstructions from vents and ducts
Furnace won't start	Tripped limit switch	Reset switch after cooling; check for underlying issues
Reset button won't stay in	Switch failure or ongoing overheating	Replace switch; verify furnace temperature normal
No heat after reset	Other system issues	Check thermostat, gas valve, ignition system
Frequent cycling	Oversized furnace or airflow problems	Verify proper furnace sizing; check ductwork

Professional Service: Contact Carrier authorized technician at 1-800-CARRIER for repeated issues.