Atwood 7900 Furnace Manual

The Atwood 7900 Furnace is a high-efficiency RV furnace designed for reliable heating performance. This forced-air furnace features electronic ignition, multiple heat settings, built-in safety controls, easy installation, and compatibility with 12V DC power systems. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting to Power 7. Operation 8. Maintenance 9. Safety Features 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Burner assembly, blower motor, heat exchanger, control board, thermostat, exhaust vent, intake air vent.

Feature	Description
Electronic ignition	No standing pilot light for improved efficiency
Multi-speed blower	Adjustable airflow for optimal heating
Heat exchanger	Stainless steel construction for durability
Control board	Microprocessor-controlled operation
Thermostat compatibility	Works with standard RV thermostats
Exhaust vent	Durable plastic venting system
Intake air vent	Separate combustion air intake
Safety shut-off	Automatic shut-off for safety conditions
Power requirements	12V DC operation
BTU ratings	Multiple output options available

Installation

Unpack and inspect all components. Ensure proper mounting location.

Mount furnace: Secure to floor or wall using provided brackets.
Connect ductwork: Attach heating ducts to outlet plenum.
Install vents: Connect exhaust and intake vents to outside.
Wire electrical: Connect 12V DC power and thermostat wires.
Test operation: Verify proper ignition and airflow.

WARNING! Installation must comply with local codes. Ensure proper clearances to combustible materials.

First-Time Setup

Complete installation verification before initial operation.

Check all connections: Verify electrical and vent connections are secure.
Set thermostat: Install and configure compatible thermostat.
Test ignition: Power on and verify proper ignition sequence.
Adjust blower speed: Set appropriate airflow for your application.
Verify safety controls: Ensure all safety features are functioning.

CAUTION! Never operate without proper venting. Ensure adequate combustion air supply.

Specifications

Model Series: 7900
BTU Output: 16,000 - 30,000 BTU (depending on model)
Power Source: 12V DC
Ignition: Electronic spark ignition
Blower Type: Multi-speed centrifugal
Venting: Direct vent system
Dimensions: Varies by model (check specific model label)
Weight: Approximately 15-20 pounds
Fuel Type: Propane/LP gas
Efficiency: High-efficiency heat exchanger

Controls and Settings

Operation controlled via compatible thermostat. Internal DIP switches for configuration.

Thermostat Controls: Temperature setting, fan mode (auto/on), system on/off.

Internal Settings: Blower speed adjustment, ignition timing, safety lockout timing. Access control board for diagnostic LED codes. Fan delay settings for optimal heat distribution. High altitude compensation if needed.

Connecting to Power

12V DC power connection requirements.

Disconnect power source before wiring.
Connect 12V DC positive and negative wires to control board.
Connect thermostat wires to appropriate terminals.
Ensure proper polarity and secure connections.
Verify adequate wire gauge for current draw.

Tip: Use fused power connection. Check voltage at furnace during operation.

Operation

Normal operating sequence and user controls.

Set thermostat to desired temperature.
Select heat mode on thermostat.
Furnace will initiate start sequence: blower pre-purge, ignition trial, main burner ignition.
Once ignited, blower continues operation until thermostat satisfied.
Shutdown sequence: burner off, blower post-purge.
Monitor for normal operation sounds and airflow.

WARNING! Never block vents or air intakes. Monitor for proper flame appearance.

Maintenance

Regular maintenance schedule for optimal performance.

Annual inspection: Check burner, heat exchanger, vents.
Clean air filter: Replace or clean intake air filter regularly.
Check venting: Ensure vents are clear of obstructions.
Inspect electrical: Check wiring and connections.
Verify operation: Test safety controls and ignition.

CAUTION! Disconnect power before servicing. Only qualified technicians should perform internal repairs.

Safety Features

Built-in safety systems for protection.

Safety Feature	Function
Flame rollout switch	Detects improper burner flames
Overheat limit switch	Prevents excessive temperatures
Ignition lockout	Locks out after multiple failed ignition attempts
Pressure switch	Verifies proper venting operation
Airflow sensor	Ensures adequate combustion air

Regulatory Information

CSA certified for RV use. Complies with ANSI Z21.44 standards. Manufactured to meet RV industry requirements. For technical support, contact Atwood Customer Service at 1-800-555-ATWOOD or visit www.atwoodmobile.com. Serial number located on unit rating plate.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No ignition	Power, gas supply, control issue	Check 12V power, verify gas valve open, check control board LED codes
Blower runs but no heat	Ignition failure, gas valve	Listen for spark, check gas pressure, verify valve operation
Short cycling	Overheat, airflow restriction	Check filters, verify venting clear, inspect heat exchanger
No blower operation	Motor, capacitor, control	Check voltage to motor, inspect capacitor, verify control signals
Lockout condition	Safety switch, flame sense	Reset power, check safety switches, clean flame sensor

Reset Procedure: Turn thermostat off, disconnect power for 60 seconds, restore power.

Service: 1-800-555-ATWOOD; www.atwoodmobile.com