Tempstar DC90 Furnace Manual

The Tempstar DC90 is a high-efficiency gas furnace featuring variable-speed blower technology, modulating gas valve for precise temperature control, AFUE rating up to 98%, two-stage heating operation, durable aluminized steel heat exchanger, diagnostic LED system, quiet operation, and compatibility with most thermostats. Designed for residential use with natural gas or propane capability. Below are key sections for safety, features, installation, setup, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Installation Requirements 3. First-Time Setup 4. Technical Specifications 5. Controls and Operation 6. Thermostat Connection 7. Maintenance Procedures 9. Safety Features 10. Care & Cleaning 11. Regulatory Information 12. Troubleshooting

Features at a Glance

Key components: Variable-speed ECM blower motor, modulating gas valve, aluminized steel primary heat exchanger, stainless steel secondary heat exchanger, integrated control board, pressure switches, flame sensor, igniter.

Feature	Description
Variable-speed blower	ECM motor for precise airflow control and energy efficiency
Modulating gas valve	Provides 35-100% heating capacity in 1% increments
Two-stage operation	Low and high fire stages for optimal comfort
Diagnostic LED	Flashing codes for troubleshooting
Pressure switches	Safety devices to verify proper venting
Flame sensor	Detects burner flame for safety shutdown
Hot surface igniter	Silicon carbide igniter for reliable lighting
Condensate drain	Removes condensation from high-efficiency operation
Gas connection	1/2" NPT for natural gas or propane
Electrical connection	120V AC, 60Hz power supply

Installation Requirements

Professional installation required. Verify local codes and obtain permits.

Location: Install in dry, clean area with adequate combustion air and service clearance.
Venting: Use approved PVC pipe for intake and exhaust; maintain proper slope for condensate drainage.
Gas supply: Connect to properly sized gas line with sediment trap.
Electrical: Connect to dedicated 120V circuit with proper grounding.
Ductwork: Ensure properly sized and sealed duct system.

WARNING! Gas furnaces produce carbon monoxide; proper venting is critical. Installation must comply with all local codes and manufacturer specifications.

First-Time Setup

After installation, perform initial startup procedure.

Gas pressure adjustment: Verify and adjust manifold pressure per specifications.
Blower speed settings: Configure cooling and heating speeds per installation requirements.
Thermostat configuration: Connect compatible thermostat and configure staging.
System check: Verify proper ignition sequence, airflow, and temperature rise.
Safety testing: Test limit switches, pressure switches, and flame rollout devices.

CAUTION! Only qualified HVAC technicians should perform startup procedures. Improper setup can create hazardous conditions.

Technical Specifications

Model Series: DC90
AFUE Rating: Up to 98%
Heating Capacity: 40,000-120,000 BTU/hr (varies by model)
Stages: Two-stage heating with modulating capability
Blower Type: Variable-speed ECM
Gas Type: Natural gas or propane (conversion kit required)
Electrical: 120V AC, 60Hz, 15 amp circuit
Venting: PVC pipe (2" or 3" depending on model)
Sound Level: As low as 65 dB
Warranty: Limited lifetime heat exchanger, 10 years parts

Controls and Operation

Integrated control board manages all furnace functions with diagnostic capabilities.

Control Board Features: Status LED, dip switches for configuration, terminal strip for thermostat connections, fuse protection.

Operation Modes: Standby (waiting for heat call), Prepurge (blower on), Ignition (hot surface igniter active), Main Burn (gas valve open), Run (blower circulating heated air), Postpurge (blower clearing combustion gases).

LED Flash Codes: Continuous on (normal operation), 1 flash (pressure switch error), 2 flashes (ignition failure), 3 flashes (limit switch open), 4 flashes (pressure switch stuck closed), 5 flashes (flame sensed with gas valve off).

Thermostat Connection

Compatible with most 24V thermostats including programmable and smart models.

Turn off power to furnace before connecting thermostat wires.
Connect wires to control board terminal strip: R (24V power), C (common), W/W1 (heat stage 1), W2 (heat stage 2), G (fan), Y/Y1 (cooling).
Configure thermostat for two-stage heating operation.
Restore power and test operation.

Tip: Use thermostat compatible with two-stage systems for optimal comfort and efficiency.

Maintenance Procedures

Annual professional maintenance recommended for optimal performance and safety.

Filter replacement: Replace 1" filter monthly; 4" media filter every 6-12 months.
Blower cleaning: Vacuum blower wheel and compartment annually.
Heat exchanger inspection: Visual check for cracks or corrosion.
Flame sensor cleaning: Gently clean with emery cloth.
Drain system: Flush condensate trap and clear drain lines.
Venting inspection: Check PVC pipes for obstructions or damage.
Gas pressure verification: Check manifold pressure and adjust if needed.
Safety device testing: Verify operation of all limit switches and pressure controls.

WARNING! Always turn off electrical power and gas supply before performing any maintenance. Carbon monoxide poisoning hazard exists if furnace is not properly maintained.

Safety Features

Multiple safety systems protect against hazardous conditions: Flame rollout switch (detects burner compartment overheating), High limit switch (protects against overheating), Pressure switches (verify proper venting), Flame sensor (confirms burner ignition), Ignition control (safety shutdown if flame not detected).

Care & Cleaning

Regular maintenance ensures efficient operation and extends furnace life.

Monthly: Check and replace air filter if dirty. Quarterly: Visual inspection of vent pipes and drain system. Annually: Professional cleaning and inspection.

CAUTION! Never operate furnace without filter. Keep area around furnace clear of combustible materials. Install carbon monoxide detectors in living areas.

Regulatory Information

UL listed and ANSI certified. Meets DOE efficiency standards. Manufactured in compliance with U.S. safety regulations. Natural gas models certified for altitudes up to 2,000 feet. For technical support or warranty service, contact Tempstar at 1-800-772-2179 or visit www.tempstar.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power, thermostat, door switch	Check circuit breaker, thermostat setting, ensure door properly closed.
No heat	Gas supply, igniter, flame sensor	Verify gas valve on, check for spark/flame, clean flame sensor.
Short cycling	Dirty filter, restricted airflow	Replace filter, check vents and registers.
Blower won't stop	Thermostat fan setting	Check thermostat fan setting (should be AUTO not ON).
Unusual noises	Blower, motor, ductwork	Inspect blower wheel, motor bearings, check for loose panels.
Error codes flashing	Various system faults	Count LED flashes and refer to diagnostic chart in manual.

Reset Procedure: Turn thermostat off, turn furnace power off for 30 seconds, restore power, turn thermostat on.

Service: 1-800-772-2179; www.tempstar.com