Independent fireplace insert buyer's guide
Duluth Forge Fireplace Inserts
Compare ventless gas fireplace inserts by exact model, BTU, fuel, controls and verified dimensions.
Separate indoor dual-fuel and natural-gas inserts from outdoor stainless models before checking current Amazon offers.
As an Amazon Associate I earn from qualifying purchases. Offers and availability can change.
Popular Duluth Forge Fireplace Inserts
The more recently identified FNF300T natural-gas model appears first. Outdoor inserts are clearly labeled, while older listings without a recently observed featured offer appear lower; Amazon availability is never guaranteed.
Installation matters: Product dimensions are not framing or rough-opening dimensions. Confirm the exact manual, approved installation location, fuel connection and clearances before ordering.
FNF300T · B0FH7LWK3T
Duluth Forge FNF300T: 26,000-BTU Natural Gas Thermostat Insert
A newer 300-series indoor fireplace insert configured for natural gas only, with a built-in thermostat and a compact 29.1-inch-wide body.
- Output
- 26,000 BTU
- Fuel
- Natural gas only
- Control
- Built-in thermostat
- Use
- Indoor vent-free insert
- W × H × D
- 29.1 × 23.9 × 13.9 in.
Confirm the FNF300T designation and natural-gas-only configuration.
DF450SS-G · B07YLGT2YX
Duluth Forge DF450SS-G: 24,000-BTU Outdoor Crystal-Glass Insert
A stainless outdoor gas fireplace insert with reflective crystal glass and manual controls for an approved exterior fireplace project.
- Output
- 24,000 BTU
- Fuel
- Natural gas; verify LP kit
- Control
- Manual
- Use
- Outdoor stainless insert
- W × H × D
- 31.56 × 31.56 × 13.25 in.; verify
Outdoor approval and fuel conversion components must be verified.
DF450SS-G-RCO · B07YBW4GFR
Duluth Forge DF450SS-G-RCO: 24,000-BTU Outdoor Copper-Glass Insert
A compact outdoor stainless fireplace insert with reflective copper glass, manual operation and a distinctly different body size from the crystal-glass listing.
- Output
- 24,000 BTU
- Fuel
- Natural gas; verify LP kit
- Control
- Manual / push button
- Use
- Outdoor stainless insert
- W × H × D
- 26 × 21 × 13 in.
Confirm copper-glass media, outdoor placement and fuel setup.
FDF300T · B0742S13BW
Duluth Forge FDF300T: 26,000-BTU Dual-Fuel Thermostat Insert
A compact indoor vent-free insert with 26,000 BTU, natural-gas-or-propane capability and thermostat operation for an approved built-in installation.
- Output
- 26,000 BTU
- Fuel
- Natural gas or propane
- Control
- Built-in thermostat
- Use
- Indoor vent-free insert
- W × H × D
- 29.1 × 23.9 × 13.9 in.
A recent indexed listing showed no featured offer; check sellers.
FDF400RT-ZC · B01MCVZEPP
Duluth Forge FDF400RT-ZC: 32,000-BTU Dual-Fuel Remote Insert
A 32,000-BTU indoor insert with remote controls, dual-fuel capability and a 29.1-inch-wide body for a manufacturer-approved built-in project.
- Output
- 32,000 BTU
- Fuel
- Natural gas or propane
- Control
- Remote
- Use
- Indoor built-in insert
- W × H × D
- 29.1 × 29.5 × 15.6 in.
Verify remote inclusion, installation approval and current sellers.
FDI32R · B017XS5JM0
Duluth Forge FDI32R: 32,000-BTU Full-Size Dual-Fuel Remote Insert
A larger indoor ventless gas insert with remote operation, nine ceramic logs and a substantially wider body than the 29.1-inch FDF models.
- Output
- 32,000 BTU
- Fuel
- Natural gas or propane
- Control
- Remote
- Use
- Full-size indoor insert
- W × H × D
- 36.38 × 33.27 × 18.38 in.
Check the wider body, required framing and current seller offer.
FDF400T-ZC · B074BC6VWV
Duluth Forge FDF400T-ZC: 32,000-BTU Dual-Fuel Thermostat Insert
The thermostat-controlled 400-series indoor insert shares the 29.1-inch-wide body format with FDF400RT-ZC but does not imply an included remote.
- Output
- 32,000 BTU
- Fuel
- Natural gas or propane
- Control
- Built-in thermostat
- Use
- Indoor built-in insert
- W × H × D
- 29.1 × 29.5 × 15.6 in.
The latest indexed offer showed no featured seller; verify availability.
How We Compare Duluth Forge Fireplace Inserts
The most important differences are not visible in a similar product photo. Compare installation location, fuel certification, body dimensions and control type before choosing a model.
Indoor versus outdoor approval
FNF300T, FDF300T, FDF400RT-ZC, FDF400T-ZC and FDI32R are indoor insert listings. DF450SS-G and DF450SS-G-RCO are outdoor stainless models and must not be substituted into an indoor project.
Useful body-size comparisons
Compact 300-series bodies measure about 29.1 inches wide by 23.9 inches high. The 400-series bodies are about 29.1 inches wide by 29.5 inches high. FDI32R is approximately 36.38 inches wide.
Fuel, controls and seller clarity
FNF300T is natural-gas-only, while the compared FDF and FDI indoor listings are dual fuel. Thermostat, remote and manual controls are different packages, and older listings can lack a featured seller.
Duluth Forge Fireplace Insert Comparison Table
Dimensions below are stated consistently as product width × height × depth. They describe the appliance body only and must not be used as the required framing opening.
| Model | Use | Output | Fuel | Control | Width × height × depth | Offer or fit note |
|---|---|---|---|---|---|---|
| FNF300T | Indoor vent-free | 26,000 BTU | Natural gas only | Thermostat | 29.1 × 23.9 × 13.9 in. | Newer model; verify current offer |
| DF450SS-G | Outdoor stainless | 24,000 BTU | Natural gas; verify LP kit | Manual | 31.56 × 31.56 × 13.25 in.; verify | Crystal glass; outdoor only |
| DF450SS-G-RCO | Outdoor stainless | 24,000 BTU | Natural gas; verify LP kit | Manual / push button | 26 × 21 × 13 in. | Copper glass; outdoor only |
| FDF300T | Indoor vent-free | 26,000 BTU | Natural gas or propane | Thermostat | 29.1 × 23.9 × 13.9 in. | Check current seller offer |
| FDF400RT-ZC | Indoor built-in | 32,000 BTU | Natural gas or propane | Remote | 29.1 × 29.5 × 15.6 in. | Verify remote and seller |
| FDI32R | Full-size indoor | 32,000 BTU | Natural gas or propane | Remote | 36.38 × 33.27 × 18.38 in. | Wider body; check seller |
| FDF400T-ZC | Indoor built-in | 32,000 BTU | Natural gas or propane | Thermostat | 29.1 × 29.5 × 15.6 in. | No recent featured offer noted |
Fireplace Insert Dimensions and Installation Fit
An insert that physically appears narrower than an existing opening can still be unsuitable. Body size, approved rough opening, trim coverage, combustible clearances and gas access are separate measurements.
26,000-BTU compact indoor inserts
FNF300T and FDF300T share a body approximately 29.1 inches wide, 23.9 inches high and 13.9 inches deep. Their fuel systems differ: FNF300T is natural-gas-only; FDF300T is dual fuel.
32,000-BTU 400-series inserts
FDF400RT-ZC and FDF400T-ZC use a body approximately 29.1 inches wide, 29.5 inches high and 15.6 inches deep. The RT model is associated with remote control, while the T model uses a thermostat.
Full-size FDI32R projects
FDI32R is approximately 36.38 inches wide, 33.27 inches high and 18.38 inches deep. That extra width, height and depth makes it a different installation class from the compact FDF inserts.
Do not convert body dimensions into a cutout: Required framing, clearances, trim overlap and installation into an existing fireplace depend on the exact model's manual and local rules.
Natural Gas, Dual Fuel and Outdoor Insert Differences
A similar cabinet, flame appearance or model prefix does not make two inserts interchangeable. Match the appliance label and installation documents to the fuel and approved location.
FNF300T: natural gas only
The FNF300T is a 26,000-BTU natural-gas indoor insert with thermostat control. It should not be described as dual fuel or connected to propane unless the exact appliance documentation explicitly authorizes a conversion.
FDF and FDI: compared dual-fuel models
FDF300T, FDF400RT-ZC, FDF400T-ZC and FDI32R are listed for natural gas or liquid propane. Dual-fuel labeling does not replace the required gas-pressure, connection and approved-setup checks.
DF450SS: outdoor stainless models
DF450SS-G and DF450SS-G-RCO are outdoor project inserts with glass media and manual controls. Verify the approved exterior enclosure, weather exposure, supplied fuel configuration and any separately required conversion kit.
Remote, Thermostat and Manual Insert Controls
Remote-control inserts
FDI32R and FDF400RT-ZC are associated with remote operation. Confirm that the handset, receiver and any batteries are actually included in the selected seller package.
Thermostat-control inserts
FNF300T, FDF300T and FDF400T-ZC use thermostat-style control. A thermostat regulates burner operation; it does not automatically mean a handheld remote is included.
Manual outdoor controls
DF450SS-G and DF450SS-G-RCO are listed with manual or push-button controls. Their outdoor use, glass media and fuel setup matter more than indoor remote-control features.
Which Duluth Forge Fireplace Insert Should You Choose?
Choose FNF300T for natural gas
Select FNF300T when the project has a natural-gas supply, needs thermostat control and calls for a compact 26,000-BTU indoor insert approved for the intended room.
Choose FDF300T for compact dual fuel
FDF300T fits the same approximate body-size class but adds natural-gas-or-propane flexibility. Confirm whether a current Amazon seller has an active offer.
Choose FDF400RT-ZC for a remote
Consider FDF400RT-ZC when the approved installation supports 32,000 BTU and a taller 400-series body, and when a remote-control package is a priority.
Choose FDF400T-ZC for thermostat control
FDF400T-ZC offers the same general 32,000-BTU body-size class as FDF400RT-ZC, but the T designation identifies thermostat-style operation instead of an assumed remote.
Choose FDI32R for a larger built-in
FDI32R is the full-size remote option. Its approximately 36.38-inch width and deeper body should be checked against an installer-approved project, not a 29-inch insert assumption.
Choose DF450SS only for outdoor work
DF450SS-G offers crystal glass and DF450SS-G-RCO offers copper glass. Both require an approved outdoor installation and are not substitutes for indoor vent-free inserts.
Before You Install a Ventless Gas Fireplace Insert
Gas-fired appliances require model-specific installation documents, suitable combustion air and code-compliant work. Have a qualified installer evaluate the project before relying on a listing photograph.
- Confirm the exact appliance and manualMatch the manufacturer model, ASIN, appliance label and production version before using installation instructions or ordering trim.
- Check the permitted installation locationIndoor vent-free inserts and outdoor stainless inserts have different approval requirements; an outdoor model must never be treated as an indoor insert.
- Measure width, height and depth separatelyCompare verified product-body dimensions, approved rough-opening measurements, trim coverage and access for servicing.
- Verify combustible clearancesFollow the exact manual for framing, finish materials, mantel clearances and ceiling distances; zero-clearance-family wording does not mean zero clearance to every material.
- Match fuel and gas pressureIdentify natural-gas-only versus dual-fuel models, approved gas connection, inlet pressure and whether a conversion kit is actually supplied and permitted.
- Confirm room and safety requirementsCheck local vent-free appliance rules, combustion-air provisions, oxygen-depletion shutoff, servicing access and properly installed carbon-monoxide alarms.
For model identification and installation-document guidance, use our Duluth Forge manuals guide.
Duluth Forge Fireplace Inserts FAQ
What is the correct model for ASIN B0FH7LWK3T?
ASIN B0FH7LWK3T is associated with Duluth Forge FNF300T, a 26,000-BTU natural-gas-only ventless fireplace insert with thermostat control. The T is important because it identifies the thermostat configuration.
Is the FNF300T a dual-fuel fireplace insert?
No. FNF300T is identified as a natural-gas-only model. The similar FDF300T is the 26,000-BTU dual-fuel insert in this comparison.
What are the dimensions of Duluth Forge FNF300T and FDF300T?
Both compared 26,000-BTU inserts are approximately 29.1 inches wide, 23.9 inches high and 13.9 inches deep. Those are product-body dimensions, not the approved framing or rough-opening measurements.
What is the difference between FDF400RT-ZC and FDF400T-ZC?
Both are 32,000-BTU dual-fuel indoor inserts with a body approximately 29.1 inches wide, 29.5 inches high and 15.6 inches deep. FDF400RT-ZC is associated with remote control, while FDF400T-ZC uses thermostat control.
How wide is the Duluth Forge FDI32R?
The FDI32R product body is approximately 36.38 inches wide, 33.27 inches high and 18.38 inches deep. Its larger size makes it different from the approximately 29.1-inch-wide FDF and FNF insert families.
Are DF450SS-G and DF450SS-G-RCO suitable for indoor use?
No. These listings describe outdoor stainless fireplace inserts. DF450SS-G is associated with crystal glass, while DF450SS-G-RCO is associated with copper glass. Follow the exact outdoor installation manual and approved fuel configuration.
Do ventless fireplace inserts fit into any existing fireplace?
No. Suitability depends on the exact insert, the existing fireplace construction, the manual's approved installation method, the gas line, room volume, clearances and local code. Appliance-body dimensions alone do not prove compatibility.
Where can I check Duluth Forge inserts that are available now?
Use either Amazon category-search button to check current seller offers, active model variants, shipping options and delivery estimates. Individual product availability can change at any time.