manual american furnace model sh-75-2

The American Furnace Model SH-75-2 is a high-efficiency residential heating system with 75,000 BTU output capacity, natural gas/propane compatibility, AFUE rating of 95%, two-stage heating operation, variable-speed blower motor, electronic ignition system, built-in diagnostic controls, pressure switch safety, condensate drainage system, and compatibility with standard thermostat systems. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Systems 7. Operating Procedures 8. Maintenance Features 9. Care & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Two-stage gas valve, variable-speed inducer motor, hot surface ignitor, flame sensor, pressure switches, condensate trap, control board with diagnostic LED.

Feature	Description
Gas valve	Two-stage operation for improved efficiency
Inducer motor	Variable-speed for optimal combustion
Hot surface ignitor	Electronic ignition system
Flame sensor	Safety feature to detect flame presence
Pressure switches	Verify proper venting conditions
Condensate trap	Collects and drains condensation
Control board	Microprocessor with diagnostic capabilities
Blower motor	Variable-speed ECM for efficient airflow
Heat exchanger	Stainless steel primary and secondary
Thermostat connections	Standard 24V connections

Installation

Unpack and inspect contents. Ensure proper location with adequate clearance.

Gas connection: Use approved gas piping; apply leak detection solution.
Vent system: Install PVC vent pipes per local codes; maintain proper slope.
Electrical: Connect 120V power supply; install disconnect switch within sight.
Thermostat: Connect 24V thermostat wires to control board.
Condensate: Route drain line to suitable drainage point.

WARNING! Gas appliances can be dangerous; only qualified technicians should install. Ensure proper ventilation.

First-Time Setup

Power on furnace; follow startup sequence.

Gas pressure check: Verify inlet and manifold pressures per specifications.
Vent verification: Confirm proper draft and venting operation.
Blower settings: Adjust dip switches for proper airflow configuration.
Thermostat configuration: Set up heating stages and fan control.
Combustion analysis: Verify CO levels and efficiency readings.

CAUTION! Never bypass safety controls. Test all safety functions before operation.

Specifications

Heating Capacity: 75,000 BTU/hr input
AFUE Rating: 95%
Stages: Two-stage heating operation
Motor Type: Variable-speed ECM blower
Gas Type: Natural gas (convertible to propane)
Voltage: 120V AC, 60Hz
Control Voltage: 24V AC
Vent Size: 2" or 3" PVC
Operating Temp Range: -30°F to 150°F ambient
Dimensions: 44" H x 21" W x 26" D

Controls and Settings

Access control board via front panel. Diagnostic LED provides status codes.

Dip Switch Settings: Blower speeds, heating stages, accessory configuration.

Heating: Two-stage operation with adjustable timing. Blower: Variable-speed with multiple airflow settings. Safety: Pressure switches, flame rollout, high limit controls. Diagnostics: LED flash codes for troubleshooting (1-7 flashes indicate specific faults).

Connecting Systems

Thermostat: Standard 24V connections. Vent: PVC piping. Gas: 1/2" or 3/4" black iron.

Turn off power and gas supply before connecting.
Match thermostat wires to correct terminals (R, W, G, C).
Ensure vent pipes are properly glued and supported.
Test gas connections with leak detection solution.

Tip: Always use approved materials and follow local building codes.

Operating Procedures

Normal heating cycle operation.

Call for heat: Thermostat signals furnace to begin cycle.
Inducer motor: Starts to establish draft.
Pressure switch: Verifies proper venting conditions.
Ignition: Hot surface ignitor heats up.
Gas valve: Opens first stage for ignition.
Flame sensor: Confirms flame establishment.
Second stage: Engages if needed for higher demand.
Blower: Starts after heat exchanger warm-up period.
Shutdown: Follows reverse sequence when thermostat satisfied.

WARNING! Do not attempt to manually override safety controls. Contact qualified technician for service.

Maintenance Features

Self-diagnostics: LED status codes indicate system conditions. Air filter monitoring: Reminder for filter changes. Safety shutdown: Automatic protection for fault conditions.

Care & Cleaning

Turn off power before maintenance. Replace air filter monthly during heating season. Clean flame sensor annually. Inspect vent system for obstructions.

CAUTION! Never operate without filter. Keep combustion area clear of debris.

Regulatory Information

ANSI Z21.47: Certified for natural gas operation. UL listed for safety. Meets DOE efficiency standards. For support, contact American Furnace technical service at 1-800-555-HEAT or visit www.americanfurnace.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No heat	Power/thermostat/gas	Check power supply; verify thermostat setting; ensure gas valve open.
Furnace locks out	Safety device tripped	Check LED code; reset power; inspect flame sensor and pressure switches.
Blower not running	Motor/control issue	Verify thermostat fan setting; check blower motor and capacitor.
Ignition failure	Ignitor/sensor	Inspect hot surface ignitor; clean flame sensor; check gas pressure.
Short cycling	Airflow/limit switch	Replace dirty filter; check for blocked vents; verify limit switch operation.

Reset: Power cycle to clear lockout conditions.

Service: 1-800-555-HEAT; www.americanfurnace.com