Dayton Furnace Model 3438B Manual

The Dayton Furnace Model 3438B is a high-efficiency residential gas furnace with 80,000 BTU input capacity, single-stage operation, multi-speed blower motor, electronic ignition, and durable heat exchanger construction. Designed for reliable heating performance with safety features including flame rollout protection, limit switches, and pressure switches. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation Requirements 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Venting and Combustion Air 7. Operation Instructions 8. Maintenance Procedures 9. Safety Features 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Heat exchanger, blower assembly, gas valve, electronic ignition system, control board, pressure switches, limit controls.

Feature	Description
Heat Exchanger	Durable aluminized steel construction
Blower Motor	Multi-speed ECM motor for efficient airflow
Ignition System	Hot surface electronic ignition
Gas Valve	Single-stage automatic gas control
Control Board	Integrated furnace controller with diagnostic LEDs
Pressure Switches	Verify proper draft and venting
Limit Controls	Prevent overheating conditions
Flame Sensor	Monitors burner flame presence
Filter Rack	Standard 1-inch filter accommodation
Service Light	LED indicator for diagnostic codes

Installation Requirements

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

Location: Install in approved locations with proper clearances to combustibles.
Venting: Use approved PVC or metal vent materials per local codes.
Gas Connection: Use black iron pipe with proper thread sealant.
Electrical: Connect to 120V AC power with proper grounding.
Ductwork: Ensure proper sizing and sealing of supply/return ducts.

WARNING! Installation must be performed by qualified HVAC technician. Gas appliances can be hazardous if improperly installed.

First-Time Setup

Complete installation verification and initial startup procedure.

Verify all connections: Gas, electrical, venting, and ductwork.
Check gas pressure: Adjust manifold pressure if necessary.
Set blower speeds: Configure cooling and heating speeds per requirements.
Test operation: Complete startup sequence and verify proper operation.
Check temperature rise: Ensure within specified range (35-65°F).

CAUTION! Never operate furnace without proper venting and combustion air. Carbon monoxide hazard exists.

Specifications

Model: Dayton 3438B
Input Capacity: 80,000 BTU/H
Output Capacity: 64,000 BTU/H (80% AFUE)
Gas Type: Natural Gas (convertible to LP)
Electrical: 120V AC, 60Hz, 5.8 Amps
Blower Motor: Multi-speed ECM
Airflow: 800-1400 CFM
Venting: Category IV (PVC approved)
Dimensions: 21" W x 21" D x 46" H
Weight: 98 lbs

Controls and Settings

Access control board via front panel. Thermostat connections: R, W, G, Y, C.

Control Board: Integrated furnace controller with diagnostic LED, dip switch settings for blower speeds, gas valve control.

Blower Settings: Cooling speed, heating speed, continuous fan speed. Limit Settings: High limit control factory set at 200°F. Pressure Switch: Verifies inducer operation. Gas Valve: Single-stage operation with manual shutoff.

Venting and Combustion Air

Category IV vent system required. PVC pipe approved for venting and combustion air.

Vent Pipe: 2" or 3" PVC Schedule 40 pipe.
Combustion Air: Separate intake pipe or direct vent configuration.
Terminations: Roof or sidewall with proper clearances.
Slope: Horizontal runs slope upward 1/4" per foot toward furnace.

Tip: Always verify proper draft and combustion with combustion analyzer during installation.

Operation Instructions

Normal heating cycle operation and thermostat settings.

Thermostat Call: Set thermostat above room temperature for heat call.
Startup Sequence: Inducer motor starts, pressure switch proves, hot surface igniter glows.
Gas Valve: Opens after igniter warmup, burner ignition occurs.
Blower Operation: Blower starts after heat exchanger warmup period.
Shutdown: Gas valve closes when thermostat satisfied, blower continues for post-purge.

WARNING! Never adjust gas pressure without proper tools and training. Improper adjustment can create hazardous conditions.

Maintenance Procedures

Regular maintenance required for optimal performance and safety.

Monthly: Check and replace air filter as needed.
Annual: Professional inspection and cleaning.
Burner Cleaning: Remove and clean burners annually.
Heat Exchanger: Visual inspection for cracks or damage.
Blower Assembly: Clean blower wheel and housing.
Venting: Inspect vent system for obstructions or damage.

Safety Features

Multiple safety devices protect against hazardous conditions.

Safety Device	Function
Flame Rollout Switch	Detects flame outside burner compartment
High Limit Switch	Prevents overheating of heat exchanger
Pressure Switches	Verify proper inducer operation and venting
Flame Sensor	Confirms burner ignition for gas valve operation
Gas Valve	Automatic shutoff if ignition fails

Regulatory Information

ANSI Z21.47/CSA 2.3: Certified for natural gas operation. UL listed. Must be installed in accordance with National Fuel Gas Code (NFPA 54) and local codes. For technical support, contact Dayton Customer Service at 1-888-336-6155 or visit www.dayton.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, safety lockout	Check power supply, thermostat settings, reset lockout
No heat	Gas supply, ignition failure	Verify gas valve on, check for ignition attempts
Short cycling	Dirty filter, limit switch	Replace filter, check airflow, verify limit operation
Blower won't run	Motor, capacitor, control	Check motor operation, capacitor, control board signals
Lockout condition	Ignition failure, safety trip	Reset power, check flame sensor, verify gas pressure

Reset Procedure: Turn power off for 30 seconds, then restore.

Service: 1-888-336-6155; www.dayton.com