Atwood 8500 Furnace Manual

The Atwood 8500 Furnace is a high-efficiency RV furnace designed for reliable heating in recreational vehicles. This forced-air furnace features automatic ignition, multiple safety controls, thermostat operation, and is powered by 12V DC with LP gas fuel. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

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

Features at a Glance

Key components: Combustion chamber, blower motor, sail switch, limit switch, gas valve, thermostat, exhaust system.

Feature	Description
Automatic ignition	Electronic spark ignition for reliable startup
Forced-air system	Efficient heat distribution throughout RV
Multiple safety switches	Limit switch, sail switch, rollout protection
Thermostat control	Precise temperature regulation
LP gas operation	Clean-burning propane fuel
12V DC power	Compatible with RV electrical systems
Compact design	Space-saving installation
Durable construction	Long-lasting performance in RV environments

Installation

Unpack and inspect all components. Ensure proper ventilation and clearances.

Mount furnace: Secure to floor or wall with provided hardware.
Connect ductwork: Attach heat ducts to outlet plenum.
Install venting: Connect combustion air intake and exhaust pipes.
Wire electrical: Connect 12V DC power and thermostat wires.
Connect gas line: Use approved LP gas flex line with proper fittings.

WARNING! Installation must comply with RVIA standards and local codes. Use only certified LP gas technicians.

First-Time Setup

Complete installation checks before initial operation.

Check gas connections: Test for leaks with soap solution.
Verify electrical: Ensure proper 12V DC polarity and grounding.
Test ventilation: Confirm clear air intake and exhaust paths.
Initial startup: Set thermostat to call for heat and observe ignition sequence.
Adjust airflow: Balance duct dampers for even heat distribution.

CAUTION! Never operate without proper ventilation. Carbon monoxide hazard exists.

Specifications

Model: Atwood 8500 Series
BTU Output: Various models from 16,000 to 30,000 BTU
Fuel Type: LP Gas (Propane)
Power Requirements: 12V DC
Ignition: Electronic spark
Airflow: Forced-air blower system
Dimensions: Compact RV-specific sizing
Weight: Approximately 15-20 pounds
Venting: Direct vent system

Controls and Settings

Primary control via wall thermostat. Internal furnace controls include limit switch, sail switch, gas valve.

Thermostat Operation: Set desired temperature; furnace cycles automatically.

Internal Controls: Limit switch prevents overheating, sail switch ensures airflow before ignition, gas valve regulates fuel flow.

LED Indicators: Some models include diagnostic LED for troubleshooting.

Connecting Components

Proper connections ensure safe and efficient operation.

Gas line: Use approved flexible gas connector with leak-checked fittings.
Electrical: Connect 12V DC positive and negative wires to furnace terminal block.
Thermostat: Wire according to color coding (typically red and white wires).
Ductwork: Secure heat ducts with foil tape or proper connectors.
Venting: Install intake and exhaust pipes with proper slope and clearances.

Tip: Always turn off gas and disconnect power before making connections.

Operation

Normal heating cycle sequence:

Thermostat calls for heat
Blower motor starts (sail switch confirms airflow)
Ignition system activates (spark igniter)
Gas valve opens (with proven ignition)
Burner lights and heating begins
Blower continues until thermostat satisfied
Gas valve closes, blower runs for cool-down

WARNING! Never block air intake or exhaust vents. Maintain clear combustion air supply.

Safety Features

Multiple safety systems protect against hazardous conditions:

Limit Switch: Shuts off gas if overheating detected
Sail Switch: Prevents ignition without proper airflow
Rollout Protection: Stops operation if flame rollout occurs
Gas Valve Safety: Automatic shutoff if ignition fails
Overcurrent Protection: Circuit breaker for electrical safety

Maintenance & Cleaning

Regular maintenance ensures optimal performance and safety.

Annual inspection by qualified technician
Clean burner assembly and orifice
Vacuum combustion chamber and heat exchanger
Check and clean air intake and exhaust passages
Inspect electrical connections and wiring
Test all safety controls

CAUTION! Disconnect power and gas supply before performing any maintenance.

Regulatory Information

Certified to ANSI Z21.44/CSA 2.3 for recreational vehicle heaters. Complies with RVIA standards. Manufactured to meet industry safety requirements. For technical support, contact Atwood Customer Service at 1-800-555-ATWOOD or visit www.atwoodmobile.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, fuse	Check 12V power, thermostat setting, replace fuse if blown
No heat (blower runs)	Gas supply, ignition	Verify LP gas supply, check for spark at igniter
Short cycling	Airflow, high limit	Clean filters, check duct obstructions, verify limit switch
Blower doesn't run	Motor, sail switch	Test blower motor, check sail switch operation
Gas odor	Leaks, incomplete combustion	Immediately shut off gas; check for leaks; verify proper combustion

Reset: Turn thermostat off, wait 5 minutes, then reset.

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