Lennox Pulse Furnace Service Manual

The Lennox Pulse Furnace is a high-efficiency gas furnace featuring pulse combustion technology, electronic ignition, variable-speed blower, and advanced diagnostic systems. This service manual covers installation, operation, maintenance, troubleshooting, and repair procedures for certified HVAC technicians. Below are key sections for safety, technical specifications, installation guidelines, operation procedures, maintenance schedules, and troubleshooting.

1. Technical Specifications 2. Safety Precautions 3. Installation Guidelines 4. System Operation 5. Control Systems 6. Electrical Connections 7. Gas Supply Requirements 8. Venting Systems 9. Maintenance Procedures 10. Troubleshooting Guide 11. Parts List

Technical Specifications

Key components: Pulse combustion chamber, heat exchanger, induced draft fan, gas valve, control board, pressure switches, ignition system.

SpecificationDescription
Input Capacity40,000 - 140,000 BTU/H (model dependent)
AFUE RatingUp to 97% efficiency
Gas TypeNatural Gas or LP (conversion kit required)
Electrical Requirements120V AC, 60Hz, 15 Amp circuit
Combustion AirDirect vent or sealed combustion
VentingPVC or CPVC plastic pipe
Blower MotorVariable speed ECM
Control SystemMicroprocessor-based with diagnostics
DimensionsVaries by model (check specific model data)
Weight90 - 150 lbs (model dependent)

Safety Precautions

Critical safety procedures for installation and service.

  1. Disconnect electrical power before servicing.
  2. Shut off gas supply before working on gas connections.
  3. Verify proper venting before operation.
  4. Use approved materials for gas and vent connections.
  5. Wear appropriate PPE during service.

WARNING! Gas furnaces can produce carbon monoxide. Ensure proper venting and combustion air supply. Test for gas leaks with approved leak detection solution.

Installation Guidelines

Proper installation procedures for certified technicians.

  1. Location selection: Indoor, protected from weather, adequate clearance for service.
  2. Combustion air: Ensure adequate fresh air supply for combustion.
  3. Venting: Install PVC/CPVC vent pipes according to manufacturer specifications.
  4. Gas connection: Use approved pipe thread compound and test for leaks.
  5. Electrical: Connect to dedicated 120V circuit with proper grounding.
  6. Ductwork: Size according to heating load calculation.

CAUTION! Installation must comply with local codes and manufacturer specifications. Improper installation can cause fire, explosion, or carbon monoxide poisoning.

System Operation

Pulse combustion technology operation sequence.

  1. Call for heat: Thermostat closes R-W circuit.
  2. Pre-purge: Induced draft fan operates to clear combustion chamber.
  3. Ignition: Spark igniter activates, gas valve opens.
  4. Pulse combustion: Gas/air mixture ignites in combustion chamber.
  5. Heat exchange: Combustion gases transfer heat to heat exchanger.
  6. Blower operation: Circulates heated air through ductwork.
  7. Shutdown: Gas valve closes when thermostat satisfied.

Note: Pulse technology provides high efficiency through precise fuel/air mixture control.

Control Systems

Microprocessor control board with diagnostic capabilities.

Control Board: Monitors system operation, provides error codes, controls ignition sequence.

LED Status: Flashing patterns indicate system status and fault conditions. Pressure Switches: Verify proper venting and combustion air flow. Gas Valve: Modulates gas flow for efficient combustion. Ignition System: Electronic spark ignition with flame sensor. Temperature Limits: Protect against overheating.

Electrical Connections

Wiring diagrams and connection requirements.

  1. Disconnect power before making electrical connections.
  2. Follow wiring diagram for specific model.
  3. Use proper wire gauges for circuit length and load.
  4. Verify proper grounding of all components.
  5. Connect thermostat wires to appropriate terminals.

Tip: Use voltage tester to verify power is off before servicing electrical components.

Gas Supply Requirements

Natural gas and LP gas specifications.

  1. Gas pressure: Natural gas 7" WC, LP gas 11" WC.
  2. Pipe sizing: Based on BTU input and pipe length.
  3. Gas valve: Requires proper manifold pressure setting.
  4. Conversion: Use approved conversion kit for LP gas.
  5. Testing: Perform gas leak test after connections.

WARNING! Use approved gas leak detection solution. Never use open flame to check for leaks.

Venting Systems

PVC/CPVC vent pipe installation guidelines.

Supports direct vent or conventional vent configurations.

  1. Pipe material: Schedule 40 PVC or CPVC.
  2. Vent termination: Follow manufacturer clearances.
  3. Slope: Horizontal runs slope upward 1/4" per foot.
  4. Supports: Secure every 4 feet for horizontal runs.
  5. Sealing: Use approved PVC cement for joints.

CAUTION! Ensure vent pipes are properly supported and sealed to prevent combustion gas leakage.

Maintenance Procedures

Routine maintenance for optimal performance.

  1. Annual inspection: Check heat exchanger for cracks.
  2. Cleaning: Clean flame sensor and igniter.
  3. Filter replacement: Replace air filters monthly during heating season.
  4. Blower maintenance: Clean blower wheel and housing.
  5. Vent inspection: Check vent pipes for obstructions.
  6. Gas pressure: Verify proper manifold pressure.

Note: Regular maintenance extends furnace life and maintains efficiency.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
No heatPower, thermostat, gas supplyCheck circuit breaker, thermostat setting, gas valve position.
Furnace locks outPressure switch, flame sensorCheck venting, clean flame sensor, verify pressure switch operation.
Blower not operatingMotor, capacitor, control boardCheck voltage to motor, test capacitor, verify control signals.
Pulsing noiseCombustion issuesCheck gas pressure, air intake, heat exchanger condition.
Error codes flashingSystem faultsRefer to specific error code in service manual.

Reset: Power cycle furnace to clear lockout conditions.

Service: Contact certified Lennox technician for complex issues.

Parts List

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