American Hearth VFSM Series
American Hearth Vent-Free Slope Glaze Manual Ignition Gas Burner VFSM
The American Hearth Vent-Free Slope Glaze Gas Burner VFSM is designed to add realistic flame presentation and supplemental heat to an approved fireplace installation without requiring a conventional vent for vent-free operation. Available in 18-inch, 24-inch, and 30-inch configurations with natural gas or propane options, the Slope Glaze burner gives homeowners a flexible way to convert a compatible fireplace or vent-free firebox into a gas-burning heating appliance.
According to the supplied product information, this burner features manual operation and includes a thermostat variable remote control. It may be installed in an approved vent-free firebox or in a suitable existing solid-fuel-burning fireplace when all fireplace dimensions, clearances, combustion-air requirements, gas-supply requirements, and local codes are satisfied. It may also be installed as a vented decorative appliance when the installation is configured according to the manufacturer's instructions.
Important: This is a gas-burning heating appliance. Installation, gas piping, testing, service, and fireplace preparation should be completed by a qualified installer in accordance with the manufacturer's instructions and applicable local codes.
18 / 24 / 30 in.Available burner sizes
26,000–38,000 BTUInput range by size
Natural Gas or PropaneFuel options
Vent-Free / VentedInstallation modes
Quick Product Overview
| Brand |
American Hearth |
| Product Type |
Vent-Free Slope Glaze Gas Burner |
| Product Series |
VFSM, as provided in the product information |
| Available Sizes |
18", 24", and 30" |
| Fuel Options |
Natural Gas or Propane |
| Ignition |
Manual, according to the supplied product information |
| Heat Output |
26,000 to 38,000 BTU depending on size and configuration |
| Primary Application |
Supplemental room heating and fireplace flame presentation |
| Vent-Free Installation |
Yes, when installed in an approved application and permitted by local codes |
| Vented Decorative Installation |
Supported when installed according to manufacturer vented-installation requirements |
| Included Control |
Thermostat variable remote control, according to the supplied product information |
| Product Scope |
Burner assembly; verify required logs and other components for the selected configuration |
What Are the Key Features of the American Hearth Vent-Free Slope Glaze Gas Burner?
Vent-Free Supplemental Heating
The burner is designed for vent-free operation where permitted, allowing it to provide supplemental room heat without relying on an operating chimney flue. Because an unvented appliance uses air from the room for combustion, adequate combustion and ventilation air must be available.
Natural Gas or Propane Options
Choose the version that matches the property's existing fuel supply. Natural gas and propane models have different regulator and inlet-pressure requirements, so the correct fuel-specific version must be selected before installation.
18", 24", and 30" Burner Sizes
Multiple burner sizes make it easier to match the appliance to different fireplace openings. The fireplace must meet the minimum dimensions required for the selected burner size before installation begins.
Variable Heat Output by Size
Based on the product specifications supplied for this listing, the burner range extends from 26,000 BTU at the low end of the 18-inch configuration to a maximum of 38,000 BTU for the 30-inch configuration.
Vent-Free or Vented Installation Flexibility
The burner may be used as an unvented heater in an approved installation or configured as a vented decorative appliance when the fireplace, chimney, damper, and installation procedure comply with the manufacturer's requirements.
Existing Fireplace Installation Potential
The system may be installed in a suitable solid-fuel-burning masonry or qualifying factory-built fireplace when the fireplace is properly prepared and all sizing, clearance, ventilation, and code requirements are satisfied.
ODS Pilot Safety System
The manufacturer's vent-free burner platform uses an oxygen-depletion-sensing pilot system designed to shut the heater down if adequate fresh air is not available. This safety system must never be modified or bypassed.
Decorative Ember and Lava Rock Effects
The manufacturer's installation instructions describe glowing ember material and decorative lava rock placement to support a more natural fireplace appearance. These materials must be positioned exactly as instructed so burner operation is not obstructed.
Who Is This Burner Best For?
Good Fit
- Homeowners seeking supplemental heat from an existing compatible fireplace.
- Projects where a vent-free gas burner is permitted by local codes.
- Approved vent-free firebox installations.
- Suitable masonry or qualifying factory-built solid-fuel fireplaces.
- Homes with an appropriately sized natural gas or propane supply.
- Buyers who want a traditional gas-fire presentation without installing a new direct-vent system.
- Installations requiring 18", 24", or 30" burner sizing options.
Consider Another Fireplace Solution If
- Vent-free gas appliances are prohibited by your state or local code.
- You need a primary whole-home heating system rather than supplemental room heat.
- Your fireplace does not meet the required minimum opening dimensions or clearances.
- Your installation cannot provide adequate combustion and ventilation air.
- You require a sealed-combustion direct-vent fireplace system.
- Your existing factory-built fireplace specifically prohibits the use of unvented gas logs.
- You need to convert a burner from one fuel type to another in the field.
Size and BTU Options
The following capacity information reflects the product details supplied for this listing. Confirm the exact model, fuel type, rating plate, and current manufacturer documentation before ordering or installation.
| Burner Size |
Fuel |
Minimum Input |
Maximum Input |
| 18" |
Natural Gas |
26,000 BTU |
32,000 BTU |
| 18" |
Propane |
26,000 BTU |
32,000 BTU |
| 24" |
Natural Gas |
28,800 BTU |
36,000 BTU |
| 24" |
Propane |
28,800 BTU |
36,000 BTU |
| 30" |
Natural Gas |
30,000 BTU |
38,000 BTU |
| 30" |
Propane |
30,000 BTU |
38,000 BTU |
Selection rule: Do not choose burner size from the nominal fireplace width alone. Verify the actual front opening, rear width, depth, height, clearances, fuel supply, and manufacturer installation requirements.
Gas Pressure Specifications
| Specification |
Natural Gas |
Propane Gas |
| Regulator Pressure Setting |
3.5" W.C., based on the supplied product specification |
10.0" W.C. |
| Maximum Inlet Pressure |
10.5" W.C. |
13.0" W.C. |
| Minimum Inlet Pressure |
7.0" W.C. |
11.0" W.C. |
Gas pressure and supply-line sizing must be checked during installation. The appliance must be isolated or disconnected as required when the gas supply piping is pressure tested.
Minimum Fireplace Dimensions
The manufacturer's manual provides the following minimum fireplace dimensions for the corresponding 18", 24", and 30" burner platforms. Confirm that the exact burner being purchased is covered by these requirements before installation.
| Size |
A |
B |
C |
D |
| 18" |
17" |
14" |
28" |
17" |
| 24" |
23" |
14" |
30" |
18" |
| 30" |
26" |
14" |
34" |
20" |
Left and right clearances are determined while facing the front of the heater. If glass fireplace doors are present, they must remain open while the log set is operating, and the glass-door-frame opening is used when determining the available front opening.
Clearance Requirements
- The sides of the fireplace opening must be at least 6 inches from a combustible wall.
- For 18", 24", and 30" installations, the manufacturer's manual specifies at least 41 inches from the fireplace opening to the ceiling.
- Without a hood, noncombustible material must extend at least 12 inches above the fireplace opening.
- Noncombustible slate, marble, or similar material used in this area must be at least 1/2 inch thick.
- With the appropriate hood arrangement, the manual provides different noncombustible-material and mantel-clearance requirements.
- If the required clearances cannot be achieved, the installation must be modified according to the manufacturer's instructions rather than operating the burner in a noncompliant configuration.
Do not estimate fireplace clearances. Mantel projection, noncombustible facing, fireplace opening dimensions, and surrounding combustible construction must be checked against the installation manual.
Vent-Free Installation Requirements
When operated as an unvented room heater, the burner uses oxygen from the room in which it is installed. The installation must therefore provide adequate combustion and ventilation air. A confined space or unusually tight building construction may require additional provisions for fresh air.
The manufacturer's instructions define a confined space as an area with less than 50 cubic feet of volume per 1,000 BTU per hour of the combined input rating of appliances drawing combustion air from that space. Installation requirements must be evaluated for the entire space and all relevant fuel-burning appliances.
Do not install or operate the burner as a vent-free heater unless the room volume, fresh-air provisions, fireplace configuration, and local regulations permit the installation.
Installing the Burner in an Existing Fireplace
The manufacturer's instructions permit installation of the applicable burner system in a solid-fuel-burning masonry fireplace, a qualifying UL 127 factory-built fireplace, or a listed ventless firebox enclosure, subject to the appliance instructions and fireplace manufacturer's requirements.
Before installation into a solid-fuel-burning fireplace, the fireplace floor and chimney should be professionally cleaned of soot, creosote, ashes, and loose debris. Fresh-air vents or ash clean-out doors that could create unwanted drafting must be addressed as directed in the installation manual.
Do not install an unvented gas-log appliance in a factory-built fireplace whose instructions specifically state that the fireplace has not been tested or must not be used with unvented gas logs.
Using the Burner as a Vented Decorative Appliance
The burner platform may also be installed as a vented decorative appliance when the fireplace and chimney meet the manufacturer's requirements. In a vented installation, the flue must remain open sufficiently to vent combustion products.
A damper clamp must be installed when the log set is configured for vented operation. The clamp prevents the damper from accidentally closing. Chimney condition, minimum free-opening area, appliance input rate, and fireplace type all affect the required vented configuration.
Important: Vent-free thermostat operation and vented decorative operation are not interchangeable operating modes. Follow the manufacturer's control requirements for the way the burner is installed.
Flame Appearance and Ember Placement
After the burner has operated at full rate for approximately 10 to 15 minutes, the manufacturer's instructions describe the normal flame appearance as groups of yellow flames with intentionally random movement and varying height.
Glowing ember material should be applied lightly. Excess ember material can alter flame color and combustion characteristics. Ember material must not cover the large burner ports or the pilot assembly.
Decorative lava rock belongs on the fireplace floor in front of the burner pan. Do not place lava rock directly on the burner, logs, or glowing ember material.
Important Operating Considerations
- Do not operate the log set with fireplace glass doors closed.
- A fireplace screen must be in place during operation where required by the manufacturer's instructions.
- Do not allow fans to blow directly into the fireplace or alter the burner flame pattern.
- Do not place clothing, decorations, stockings, or other combustible materials on or near the appliance.
- Do not use an unapproved blower insert, heat exchanger insert, or accessory with the heater.
- Keep burner air openings and the control compartment clean.
- Do not operate the appliance if any control component has been under water.
- Do not modify the burner, controls, pilot safety system, gas configuration, or original appliance design.
Carbon Monoxide and Ventilation Safety
WARNING: An unvented gas heater operated without adequate combustion and ventilation air can produce carbon monoxide, an odorless poisonous gas. Do not install or use this burner as a vent-free heater until all required provisions for combustion and ventilation air have been made.
If the burner repeatedly shuts down through its oxygen-depletion safety system, do not simply relight it. Provide fresh air and have the appliance inspected if the condition continues.
Supplemental Heat, Not Whole-Home Heating
An unvented room heater is intended to provide supplemental heat to a room, not serve as the primary heat source for an entire home. Correct sizing must account for the room, combustion air, circulation, appliance input, and local installation requirements.
Gas combustion also creates water vapor. The manufacturer's documentation states that an unvented room heater produces approximately one ounce of water for every 1,000 BTU of gas input per hour. Proper sizing and ventilation help manage indoor humidity during operation.
High-Altitude Considerations
The manufacturer's documentation states that for installations above 2,000 feet elevation, appliance ratings should be reduced at a rate of 4 percent for each 1,000 feet above sea level. Contact the manufacturer or a qualified installer when planning a high-altitude installation.
Canada Installation Limitation
Canada: The manufacturer's manual states that this burner platform cannot be installed as an unvented appliance in Canada. Canadian installations covered by the manual are vented applications and must comply with the applicable Canadian installation requirements.
What's Included
Based on the supplied product description and the manufacturer's burner documentation, the package is associated with the following burner components. Exact contents should be confirmed for the specific configuration ordered.
- Slope Glaze gas burner / grate assembly
- Thermostat variable remote control, according to the supplied product information
- Anchoring hardware
- Glowing ember material
- Decorative lava rock
- Damper clamp for applicable installation
Burner configuration: The original product information identifies this listing as burner only. Confirm whether logs or any additional decorative components are included with the exact configuration being purchased.
Installation and Gas-Supply Requirements
Installation and replacement of gas piping, gas-utilization equipment, controls, and related accessories should be performed by a qualified installing agency. The installer must verify the correct gas type, gas pressure, line sizing, fireplace dimensions, clearances, combustion air, venting configuration when applicable, and all local-code requirements.
- Each appliance should have an accessible manual gas shutoff.
- Gas piping compounds must be suitable for the applicable fuel.
- Gas connections must be checked for leakage after installation.
- Never use an exposed flame to check for a gas leak.
- Do not pressure-test the appliance while it remains connected in a manner prohibited by the manual.
- The burner/grate must be secured to the fireplace floor as instructed.
- Use only the fuel type identified for the purchased appliance.
Initial Burn-In
During initial operation, manufacturing oils, coatings, and bonding agents can produce temporary smoke and odor. The manufacturer's instructions recommend operating the burner at its highest setting for approximately two to three hours while providing maximum ventilation by opening windows or doors.
Initial curing odors should diminish with use. Persistent smoke, abnormal flame behavior, excessive soot, or continuing unusual odors should be investigated rather than treated as a normal operating condition.
Cleaning and Maintenance
Annual inspection and cleaning by a dealer or qualified service technician is recommended to help prevent malfunction and sooting. Turn the heater off and allow it to cool completely before cleaning or maintenance.
- Inspect and clean burner air-intake openings.
- Inspect burner ports for lint, dust, or obstructions.
- Inspect the oxygen-depletion-sensing pilot.
- Verify proper flame pattern and log placement.
- Verify smooth main-burner ignition.
- Remove loose particles around burner and control areas.
- Do not use cleaning fluids on the logs or heater components.
Warranty Information
The supplied manufacturer's manual describes a limited five-year parts and labor warranty for covered hearth-product components, excluding remote controls, thermostats, accessories, and replacement parts. Remote controls, thermostats, accessories, and other covered parts are described as having a limited one-year parts warranty.
Warranty coverage is subject to the manufacturer's terms, including qualified installation, proper operation and maintenance, proof of purchase, exclusions, and other conditions stated in the owner's manual.
Frequently Asked Questions
Is the American Hearth Slope Glaze Gas Burner vent-free?
Yes, the burner platform is designed for vent-free operation where the installation and local codes permit it. Do not use it vent-free unless the room provides the required combustion and ventilation air.
Can the American Hearth Slope Glaze Burner be installed in an existing wood-burning fireplace?
Yes, it may be installed in a compatible solid-fuel-burning masonry or qualifying factory-built fireplace. Do not install it in a factory-built fireplace whose manufacturer prohibits unvented gas logs.
Can this burner be used with the fireplace damper closed?
A compliant vent-free installation can operate without using the chimney for venting. Do not close the damper when the burner is configured as a vented decorative appliance.
Can the burner also be installed as a vented gas log appliance?
Yes, the burner platform supports an approved vented decorative installation. A damper clamp and adequate permanent flue opening are required for vented operation.
What sizes are available for the American Hearth Slope Glaze Burner?
The supplied product listing offers 18-inch, 24-inch, and 30-inch sizes. Choose the size only after confirming the actual fireplace opening and minimum required dimensions.
What is the BTU output of the American Hearth Slope Glaze Burner?
The supplied product specifications list 26,000–32,000 BTU for the 18-inch size, 28,800–36,000 BTU for the 24-inch size, and 30,000–38,000 BTU for the 30-inch size.
Is the burner available for both natural gas and propane?
Yes, natural gas and propane configurations are available. Order the fuel-specific version that matches the installation because field conversion is not permitted.
Can I use this vent-free burner as my home's primary heating system?
No. The manufacturer's documentation identifies unvented room heaters as supplemental room heat rather than a primary heat source for an entire house.
Does a vent-free gas burner need fresh air?
Yes. A vent-free gas heater consumes room air for combustion and requires adequate combustion and ventilation air; do not install it in an unsuitable confined or unusually tight space.
Can this burner be installed in a bedroom?
The manufacturer's safety instructions prohibit an unvented room heater rated above 10,000 BTU per hour from installation in a bedroom or bathroom. These burner configurations exceed that rating.
Can this burner be installed in a bathroom?
No for the vent-free configurations listed here. The manufacturer's instructions prohibit unvented heaters above 6,000 BTU per hour in a bathroom.
Can I operate the gas logs with the fireplace glass doors closed?
No. The manufacturer's instructions require glass doors to remain open during operation; closed doors can contribute to pilot outages and severe sooting.
Does the burner need professional installation?
Yes. Gas piping, installation, testing, servicing, and appliance setup should be completed by a qualified installing agency in accordance with manufacturer instructions and local codes.
Is a damper clamp included or required?
The manufacturer's burner documentation includes a damper clamp, and it is required when the burner is installed as a vented decorative appliance.
Can this burner be installed vent-free in Canada?
No. The supplied manufacturer's manual states that Canadian installations cannot use this burner platform in an unvented application; it must be installed as a vented application.
Why does a vent-free gas burner create moisture?
Water vapor is a normal by-product of gas combustion. The manufacturer's documentation states that an unvented heater produces about one ounce of water per 1,000 BTU of gas input per hour.
Expert Recommendation
Choose the American Hearth Vent-Free Slope Glaze Gas Burner when you want supplemental gas heat and a traditional fireplace flame presentation in an appropriately sized vent-free firebox or compatible existing fireplace. The available 18", 24", and 30" sizes make it possible to match several common fireplace openings, while natural gas and propane versions allow selection based on the home's existing fuel supply.
Before ordering, verify four items: the exact burner model designation, fuel type, fireplace dimensions, and whether vent-free operation is legal and appropriate for the installation. If the fireplace cannot meet the manufacturer's clearance, combustion-air, or installation requirements, do not use this burner as a vent-free heater.
Important Model Verification Before Ordering
The product information supplied for this listing identifies the burner as VFSM. The supplied manufacturer manual identifies the covered burner families as VFSE intermittent models and VFSV variable models. Confirm the exact model number on the current product configuration or manufacturer documentation before using model-specific BTU, ignition, remote-control, or pressure data for purchase or installation.
