Moncrief Furnace Manual

The Moncrief Furnace is a high-efficiency gas heating system designed for residential use, featuring advanced combustion technology, electronic ignition, variable-speed blower motor, built-in diagnostic system, programmable thermostat compatibility, safety shut-off valves, and energy-saving modes. Rated for natural gas operation with 95% AFUE efficiency. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

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

Features at a Glance

Key components: Heat exchanger, blower assembly, gas valve, electronic control board, pressure switches, flame sensor, igniter, filter compartment.

Feature	Description
Heat exchanger	Stainless steel primary and secondary heat exchangers
Blower motor	Variable-speed ECM motor for quiet operation
Gas valve	Modulating gas valve for precise temperature control
Control board	Microprocessor-based with diagnostic LED
Pressure switches	Safety switches for combustion air flow
Flame sensor	Monitors burner flame presence
Hot surface igniter	Electronic ignition system
Filter access	Slide-out filter compartment
Drain connections	Condensate drain ports
Service switches	Power disconnect and service switches

Installation

Unpack and inspect contents. Position in approved location.

Gas connection: Use approved gas pipe; apply pipe compound to male threads only.
Vent system: Install PVC vent pipes according to local codes and manufacturer specifications.
Electrical: Connect to 120V AC power supply; install proper grounding.
Thermostat wiring: Connect low-voltage thermostat wires to control board.
Drain lines: Install condensate drain lines with proper slope.

WARNING! Installation must be performed by qualified technician. Gas leaks can cause explosion. Ensure proper ventilation.

First-Time Setup

Power on furnace; follow startup sequence.

System check: Control board performs self-diagnostic test.
Gas pressure: Verify and adjust manifold gas pressure if necessary.
Airflow: Check and adjust blower speed for proper airflow.
Thermostat programming: Set desired temperature schedules.
Combustion analysis: Verify proper combustion parameters.

CAUTION! Never bypass safety controls. Ensure clearances to combustibles are maintained.

Specifications

Heating Capacity: 40,000 to 120,000 BTU/hr
Efficiency: 95% AFUE
Fuel Type: Natural gas
Electrical: 120V AC, 60Hz
Blower Motor: Variable-speed ECM
Sound Level: Less than 70 dBA
Vent Material: PVC required
Filter Size: 16x25x1 inch standard
Warranty: 10-year heat exchanger, 5-year parts

Controls and Settings

Access settings via thermostat or control board dip switches.

Control Board: Diagnostic LED, mode selection switches, blower speed terminals.

Operating Modes: HEAT, COOL, FAN ONLY, OFF. Blower Settings: Continuous fan, auto mode. Temperature Control: Single-stage or two-stage operation. Diagnostic Codes: LED flash patterns indicate system status and error codes.

Connecting Thermostat

Compatible with most 24VAC thermostats. Standard wiring: R, W, Y, G, C terminals.

Turn off power to furnace before wiring.
Strip thermostat wires 1/4 inch.
Connect wires to corresponding terminals on control board.
Program thermostat for heating system type.

Tip: Use programmable thermostat for maximum energy savings.

Operating Modes

Supports multiple operating modes for efficiency and comfort.

Heat Mode: Primary heating operation with variable output.
Fan Mode: Continuous or intermittent blower operation.
Standby Mode: System ready but not actively heating.
Diagnostic Mode: Service mode for troubleshooting.

WARNING! Do not operate without proper ventilation. Ensure intake and exhaust vents are clear.

Safety Features

Flame Rollout Switches: Shut off gas if flame detected outside burner compartment. High Limit Switches: Prevent overheating. Pressure Switches: Ensure proper venting. Ignition Safety: Shuts off gas if ignition fails.

Maintenance & Cleaning

Turn off power and gas before maintenance. Replace air filter monthly during heating season. Clean flame sensor annually. Inspect burners and heat exchanger for corrosion.

CAUTION! Never operate with blocked vents or dirty filters. Carbon monoxide hazard.

Regulatory Information

ANSI Z21.47: Certified for natural gas operation. UL listed. Meets DOE efficiency standards. Copyright © 2025 Moncrief Heating Systems; all rights reserved. For technical support, visit www.moncriefheating.com or contact 1-800-555-HEAT.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Furnace won't start	Power/thermostat	Check circuit breaker; verify thermostat settings; ensure door switch engaged.
No heat	Gas supply/ignition	Verify gas valve on; check for ignition attempts; inspect flame sensor.
Blower doesn't run	Motor/control	Check blower motor capacitor; verify control board signals.
Frequent cycling	Filter/airflow	Replace dirty air filter; check for blocked vents or registers.
Error codes flashing	System faults	Refer to diagnostic chart in service manual; reset if applicable.

Reset: Turn power off for 30 seconds then restore.

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