1. Introduction
This manual provides comprehensive instructions for the installation, operation, and maintenance of your Mr. Heater Big Maxx MHU50NG Natural Gas Unit Heater. This unit is designed to provide a reliable heat source for spaces such as garages, barns, and workshops. It features a built-in electric high-velocity fan that draws cool air into the rear, circulates it across a heat exchanger, and then distributes warm air into the surrounding area. The heater operates on 115V AC power and supports both vertical and horizontal venting. Please consult local codes and restrictions for venting requirements.
The heater includes a durable spark ignition and a self-diagnostic control module for enhanced reliability. Proper installation and adherence to these instructions are crucial for safe and efficient operation.
2. Important Safety Information
WARNING: Improper installation, adjustment, alteration, service, or maintenance can cause property damage, injury, or death. Read the installation, operating, and maintenance instructions thoroughly before installing or servicing this equipment.
- Always ensure adequate ventilation when operating the heater.
- Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.
- Keep the area around the heater clear and free from combustible materials.
- Ensure all gas and electrical connections are made by a qualified professional and comply with local codes.
- Never operate the heater if any part is submerged in water. Immediately call a qualified service technician to inspect the heater and to replace any part of the control system and any gas control that has been submerged in water.
- Do not block the air intake or exhaust vents.
- Regularly inspect the heater for signs of damage or wear.
3. Package Contents
Verify that all components are present and undamaged upon unpacking:
- Mr. Heater Big Maxx MHU50NG Unit Heater
- 2 Angle Brackets for Ceiling Mount
- Instruction Manual
- Natural Gas to Liquid Propane (LP) Conversion Kit
4. Setup and Installation
Installation should be performed by a qualified installer in accordance with all local codes and the National Fuel Gas Code ANSI Z223.1/NFPA 54.
4.1 Mounting
The unit is designed for ceiling mounting. Use the provided angle brackets to securely attach the heater to a suitable overhead structure. A minimum mounting clearance of 1 inch is required. Ensure the mounting location allows for proper air circulation and access for maintenance.
Image: Mr. Heater Big Maxx MHU50NG unit heater installed in a garage, mounted to the ceiling. This illustrates a typical installation scenario.
4.2 Venting
The heater requires a 4-inch venting system, which is sold separately. It can be vented either vertically or horizontally. Consult local building codes for specific requirements regarding vent pipe materials, clearances, and termination points.
Image: Close-up of the power exhaust port on the Mr. Heater Big Maxx MHU50NG unit heater. This port is designed for 4-inch vertical or horizontal venting, which must be purchased separately.
4.3 Gas Connection
This unit is configured for Natural Gas (NG) operation. A Liquid Propane (LP) conversion kit is included if conversion is necessary. All gas connections must be leak-tested and performed by a qualified technician.
Image: Close-up view of the gas inlet and internal components, indicating the heater is configured for natural gas. A conversion kit for liquid propane is included.
4.4 Electrical Connection
The heater requires a 120V AC electrical supply. Ensure the electrical wiring is installed by a qualified electrician and complies with all local and national electrical codes.
Image: Close-up of the electrical wiring box on the heater, detailing the connections for 120V AC power input.
4.5 Thermostat Connection
The unit is compatible with standard 24-volt thermostats or new Wi-Fi enabled thermostats (sold separately). Connect the thermostat wiring to the designated terminals on the heater's control board.
Image: Close-up of the thermostat wiring terminals on the heater, showing connections for various thermostat functions. The heater is compatible with Wi-Fi/digital thermostats.
5. Operating Instructions
5.1 Initial Startup
- Ensure all installation steps, including gas and electrical connections, are complete and verified.
- Turn on the gas supply to the heater.
- Turn on the electrical power to the heater.
- Set your connected thermostat to the desired temperature. The heater will initiate its ignition sequence.
- Observe the heater during its first few cycles to ensure proper operation and venting.
5.2 Adjusting Airflow
The heater features adjustable air louvers to direct the warm air. Adjust these louvers to optimize heat distribution within your space.
Image: Close-up of the adjustable air louvers. These can be manually adjusted to change the direction of airflow for optimal heat distribution.
5.3 High Velocity Fan
The integrated high-velocity fan ensures efficient circulation of heated air. The fan is protected by a finger-proof guard.
Image: Close-up of the high velocity fan, featuring a finger-proof guard for safety during operation.
6. Maintenance
Regular maintenance ensures the longevity and safe operation of your heater. Always disconnect power and gas supply before performing any maintenance.
- Annual Inspection: Have a qualified service technician inspect the heater annually, including the heat exchanger, burner, and ignition system.
- Cleaning: Keep the exterior of the heater clean and free from dust and debris. Ensure the air intake and exhaust vents are unobstructed.
- Vent System Check: Periodically inspect the vent system for any blockages, leaks, or corrosion.
7. Troubleshooting
If you encounter issues with your heater, refer to the following common troubleshooting steps. For complex problems, contact a qualified service technician.
| Problem | Possible Cause | Solution |
|---|---|---|
| Heater does not ignite | No gas supply, no electrical power, thermostat setting too low, ignition system fault. | Check gas valve, verify power supply, adjust thermostat, consult manual for ignition system diagnostics. |
| Heater cycles on and off frequently | Thermostat location, oversized unit, restricted airflow. | Relocate thermostat away from direct heat, ensure proper sizing for space, check for blocked vents. |
| Insufficient heat output | Incorrect thermostat setting, blocked air filters (if applicable), improper gas pressure. | Increase thermostat setting, clean or replace filters, have gas pressure checked by technician. |
| Unusual noises | Loose components, fan motor issue, debris in fan. | Inspect for loose parts, clean fan blades, contact service technician if motor noise persists. |
8. Specifications
Detailed specifications for the Mr. Heater Big Maxx MHU50NG Unit Heater:
| Feature | Detail |
|---|---|
| Model Number | F260550 |
| Brand | Mr. Heater |
| Fuel Type | Natural Gas (LP conversion kit included) |
| Heat Output | 50,000 BTUs |
| Heating Coverage | Up to 1,667 sq ft (approximate) |
| Power Source | 120V AC |
| Product Dimensions (D x W x H) | 15" x 29" x 26" |
| Item Weight | 59.5 pounds |
| Mounting Type | Ceiling Mount |
| Venting | 4-inch Vertical or Horizontal (sold separately) |
| Thermostat Compatibility | Standard 24-volt or Wi-Fi enabled (sold separately) |
| Operating Efficiency | 80% |
| UPC | 089301605503 |
Image: Dimensional diagram of the heater, showing its height, length, and width for installation planning.
9. Warranty and Support
Mr. Heater provides the following warranty for the F260550 Big Maxx MHU50NG Natural Gas Unit Heater:
- Heat Exchanger: 10-year warranty against defects.
- All Other Parts and Burners: 3-year warranty.
For warranty claims, technical support, or to purchase replacement parts, please contact Mr. Heater customer service. Refer to the contact information provided in the original product packaging or on the official Mr. Heater website.
10. Video Resources
The following video provides an overview of the Mr. Heater Big Maxx Unit Heater series. While not specific to installation, it offers a general understanding of the product.
Video: An overview of the Mr. Heater Big Maxx Unit Heater series. This video provides general information about the product line.
