DC90 Furnace Manual

The DC90 Furnace is a high-efficiency gas furnace with advanced features including variable-speed blower motor, electronic ignition, two-stage gas valve operation, sealed combustion system, diagnostic LED lights, and compatibility with most thermostats. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Two-stage gas valve, variable-speed ECM blower motor, hot surface ignitor, flame sensor, pressure switches, diagnostic LED, gas valve, filter compartment.

Feature	Description
Two-stage gas valve	Provides high and low fire operation for efficiency
Variable-speed ECM blower	Adjusts airflow for optimal comfort and efficiency
Hot surface ignitor	Electronic ignition system for reliable starts
Flame sensor	Monitors burner flame for safety
Pressure switches	Ensures proper venting operation
Diagnostic LED	Displays error codes for troubleshooting
Filter compartment	Standard 1-inch or 4-inch media filter compatible
Gas connection	1/2-inch NPT gas line connection
Electrical connection	120V AC, 60Hz power supply
Thermostat connection	Standard 5-wire thermostat terminal block

Installation

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

1. Position furnace: Place on stable, level surface with proper clearances (1-inch minimum sides, 6-inch front).
2. Connect gas line: Use approved gas pipe and fittings; pressure test for leaks.
3. Connect electrical: 120V AC power supply with proper grounding.
4. Install venting: Use approved PVC pipe for intake and exhaust.
5. Connect thermostat: Use 18-5 thermostat wire; connect to terminal block.
6. Install air filter: Insert proper size filter in filter compartment.

WARNING! Gas furnaces produce carbon monoxide; ensure proper venting. Only qualified technicians should install.

First-Time Setup

Power on furnace; follow startup sequence.

1. Check gas supply: Ensure gas valve is open; verify gas pressure.
2. Power up: Turn on electrical power; observe LED status light.
3. Thermostat setup: Set thermostat to heat mode; adjust temperature.
4. Test operation: Verify proper ignition and flame establishment.
5. Check airflow: Ensure proper airflow from supply registers.
6. Verify safety: Confirm pressure switches and limit controls function properly.

CAUTION! Do not bypass safety controls. If furnace fails to start, check error codes.

Specifications

• Input Capacity: 60,000 - 120,000 BTU/H (model dependent)
• Efficiency: 90% AFUE minimum
• Gas Type: Natural gas (convertible to LP with kit)
• Electrical: 120V AC, 60Hz, 5-8 amps
• Blower Motor: Variable-speed ECM
• Stages: Two-stage heating operation
• Venting: 2-inch PVC intake and exhaust
• Filter Size: 16x25x1 inch standard
• Sound Level: Less than 75 dB
• Warranty: 20-year heat exchanger, 5-year parts

Controls and Settings

Access control board via front panel. Integrated control module with diagnostic LED.

Control Board: POWER switch, FUSE, TERMINAL BLOCK (R, W, G, Y, C), PRESSURE SWITCH terminals, GAS VALVE connector, IGNITOR connector.

Operation: Two-stage heating (low/high fire), variable blower speeds, diagnostic mode. Settings: Blower off delay, fan on delay, temperature rise adjustment, dip switch settings for capacity and blower operation.

Connecting Thermostat

Standard 5-wire thermostat connection: R (24V power), W (heat), G (fan), Y (cool), C (common).

1. Turn off power to furnace before wiring.
2. Route 18-5 thermostat wire from furnace to thermostat location.
3. Strip wires and connect to terminal block: R, W, G, Y, C.
4. At thermostat, connect matching wires to corresponding terminals.
5. Restore power; test heating and fan operation.

Tip: Use programmable thermostat for optimal efficiency and comfort.

Operation Modes

Two-stage heating operation with variable blower control.

1. Low-stage heating: Operates at 65% capacity for mild weather
2. High-stage heating: Full capacity operation for cold weather
3. Fan only: Continuous or intermittent fan operation
4. Standby: System ready, awaiting thermostat call
5. Lockout: Safety shutdown after multiple ignition attempts
6. Diagnostic: LED flash codes for troubleshooting

WARNING! Do not operate with access panels removed. Keep combustible materials away from furnace.

Maintenance Procedures

Regular maintenance ensures optimal performance and safety.

1. Monthly: Check and replace air filter as needed
2. Seasonal: Inspect burners and heat exchanger
3. Annual: Professional inspection and cleaning
4. As needed: Clean flame sensor and ignitor
5. Check venting: Ensure intake and exhaust are clear
6. Verify operation: Test safety controls and limit switches

CAUTION! Turn off gas and electrical power before performing maintenance.

Safety Features

Multiple safety systems protect against hazardous conditions.

Safety Feature	Function
Flame rollout switches	Detects flame outside combustion chamber
High limit switch	Prevents overheating
Pressure switches	Ensures proper venting operation
Flame sensor	Confirms burner ignition
Gas valve	Automatic shutoff if no ignition
Fuse protection	Electrical circuit protection

Regulatory Information

ANSI Z21.47: Certified for natural gas and propane operation. UL listed. Meets DOE efficiency standards. CSA certified. For technical support, contact manufacturer at 1-800-555-HEAT or visit www.dc90furnace.com. Installation must comply with local building codes and NFPA 54.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, door switch	Check power supply; verify thermostat setting; ensure door switch engaged.
No heat	Gas supply, ignitor, flame sensor	Verify gas valve open; check ignitor; clean flame sensor.
Short cycling	Filter, limit switch, airflow	Replace filter; check limit switch; verify proper airflow.
Blower not working	Motor, capacitor, control board	Check motor operation; test capacitor; verify control board output.
Lockout mode	Ignition failure, safety trip	Reset power; check error code; verify gas and ignition.

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

Service: 1-800-555-HEAT; www.dc90furnace.com