Introduction
This manual provides essential information for the safe and efficient operation, installation, and maintenance of your Dometic DFMD 20121 Medium Furnace. The Dometic DFMD 20121 is a compact, low-profile furnace designed for recreational vehicles, offering reliable heating with a 20,000 BTU output. It is engineered for ease of maintenance and superior air delivery, ensuring comfortable indoor temperatures.
Setup and Installation
The Dometic DFMD 20121 Medium Furnace is designed for flexible installation, allowing for either horizontal or vertical configuration to best suit your RV's layout. Ensure that the installation location provides adequate clearance for proper ventilation and access for future maintenance.
Figure 1: Dometic DFMD 20121 Medium Furnace. This image displays the furnace unit, highlighting its compact design and the included duct adaptors. The unit's label, visible on the side, confirms the model number DFMD20121. The furnace is designed for easy integration into various RV heating systems.
The unit operates on a 12V DC power supply and utilizes LP (Liquid Propane) gas for heating. Proper connection to both the electrical system and the LP gas supply is crucial for safe and efficient operation. Refer to the detailed installation manual provided with your product for specific wiring diagrams, gas line connections, and venting requirements. Duct adaptors are included to facilitate connection to your RV's existing ductwork.
Operating Instructions
The Dometic DFMD 20121 furnace is controlled via an external thermostat (not included with the furnace unit). To operate the furnace:
- Ensure LP Gas Supply: Verify that your RV's LP gas tanks are open and have sufficient fuel.
- Power On: Ensure the 12V DC power supply to the furnace is active.
- Set Thermostat: Adjust your RV's thermostat to the desired temperature. The furnace will automatically ignite and begin heating when the ambient temperature falls below the set point.
- Monitor Operation: The furnace is designed for quiet operation due to reduced air turbulence. Listen for the fan to start and the burner to ignite. Warm air should begin to flow from the vents shortly after ignition.
- Shut Down: To turn off the furnace, set the thermostat to its lowest setting or turn it off completely. Ensure the LP gas supply is closed when the RV is stored or not in use for extended periods.
For optimal performance, ensure all air vents are unobstructed and clean.
Maintenance
The Dometic DFMD 20121 furnace is engineered for easy maintenance. Regular maintenance helps ensure efficient operation and extends the lifespan of your unit. It is recommended to perform the following checks annually or before each heating season:
- Clean Air Intake and Exhaust Vents: Ensure that the exterior intake and exhaust vents are free from obstructions such as dirt, debris, or insect nests.
- Inspect Ductwork: Check all internal duct connections for leaks or disconnections. Ensure warm air can flow freely to all registers.
- Check Electrical Connections: Verify that all electrical connections are secure and free from corrosion.
- Inspect LP Gas Line: Visually inspect the gas line for any signs of damage or leaks. If a gas odor is detected, immediately shut off the LP gas supply and ventilate the area. Do not operate the furnace until the leak is repaired by a qualified technician.
- Professional Servicing: For internal component inspection, burner cleaning, and gas pressure checks, it is highly recommended to have the furnace serviced by a qualified RV technician every one to two years.
Troubleshooting
This section provides solutions to common issues you might encounter with your Dometic DFMD 20121 furnace. For problems not listed here, or if solutions do not resolve the issue, contact a qualified service technician.
| Problem | Possible Cause | Solution |
|---|---|---|
| Furnace does not ignite or produce heat. | No LP gas supply; Low 12V DC power; Thermostat set too low; Safety lockout. | Check LP gas tank levels and ensure valves are open. Verify battery voltage. Increase thermostat setting. Turn off furnace power for 30 seconds, then restart to reset safety lockout. |
| Fan runs but no heat. | Ignition failure; Blocked exhaust/intake. | Check for obstructions in exhaust and intake vents. If problem persists, professional service is required for ignition system diagnosis. |
| Furnace cycles on and off too frequently. | Restricted airflow; Thermostat location issues. | Ensure all return air and supply registers are unobstructed. Verify thermostat is not in direct sunlight or near another heat source. |
| Unusual noises from furnace. | Loose components; Blower motor issue. | Inspect for loose panels or debris. If noise persists or is grinding/squealing, contact a qualified technician. |
Specifications
| Feature | Detail |
|---|---|
| Brand | Dometic |
| Model Number | DFM (DFMD 20121) |
| BTU Output | 20,000 BTU |
| Power Source | 12V DC |
| Fuel Type | LP Gas (Liquid Propane) |
| Dimensions (H x W x D) | 7-3/8 in. x 16-1/2 in. x 20 in. |
| Item Weight | 33.5 Pounds |
| Control Type | Button Control (via external thermostat) |
| Special Feature | Compact, Low-profile design |
| Certification | ETL |
| UPC | 0713814220365 |
Warranty and Support
For specific warranty information regarding your Dometic DFMD 20121 Medium Furnace, please refer to the warranty card included with your product packaging or visit the official Dometic website. Warranty terms and conditions may vary.
Should you require technical assistance, parts, or service, please contact Dometic customer support. Ensure you have your product model number (DFMD 20121) and serial number (if available on your unit) ready when contacting support for faster service.
Important Safety Notice: This product can expose you to chemicals including arsenic, which is known to the State of California to cause cancer. For more information, go to www.P65Warnings.ca.gov.
