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Understanding ANSI Z21.17-1998 (CSA 2.7-M98): Domestic Gas Conversion Burners Standard
Comprehensive guide to the scope, technical requirements, and compliance for gas conversion burners
ANSI Z21.17-1998, jointly published as CSA 2.7-M98, establishes uniform requirements for the construction, performance, and safe operation of domestic gas conversion burners. These burners are intended for field installation in existing heating appliances—such as furnaces, boilers, and warm-air heaters—to convert them from one gas to another (e.g., natural gas to LP-gas) or to replace a worn or inefficient burner assembly. This standard is widely referenced by manufacturers, testing laboratories, and code authorities across North America. The following article provides a detailed overview of its scope, key technical provisions, implementation guidance, and compliance notes.
Scope of ANSI Z21.17-1998 (CSA 2.7-M98)
The standard covers domestic gas conversion burners that are designed for attachment to, or installation in, appliances originally certified for use with a different gas type or requiring a replacement burner. The scope explicitly includes:
- Burners for input ratings up to 400,000 Btu/h (117 kW) for natural gas and 300,000 Btu/h (88 kW) for LP-gas.
- Conversion of appliances from natural gas to propane (LP-gas) or vice versa.
- Replacement of the original burner assembly with a new conversion burner that meets the original appliance’s performance specifications.
- Both automatic and manually operated conversion burners, including those with or without integral draft hoods and controls.
Important: ANSI Z21.17-1998 does not apply to gas burners originally supplied as part of a listed appliance; it addresses only those sold separately for retrofit or conversion purposes. Also excluded are burners designed for industrial applications or outdoor cooking equipment.
The standard aligns with the broader Z21 series of safety requirements for gas-fired appliances and is referenced in model building codes such as the NFPA 54 (National Fuel Gas Code) and the International Fuel Gas Code (IFGC).
Technical Requirements
ANSI Z21.17-1998 prescribes a comprehensive set of criteria covering construction, materials, performance, and safety. Below are the major categories.
Construction and Materials
- Burner head and manifold: Must be fabricated from corrosion-resistant materials (stainless steel, aluminized steel, or equivalent).
- Orifice and spud: Provided with the correct sizing for the intended gas type and input rating; interchangeability restrictions apply.
- Primary air adjustment: Means for adjusting primary air must be lockable to prevent accidental misalignment.
- Mounting and sealing: The burner assembly must fit the existing appliance opening without leakage and must be mechanically secure.
Performance and Safety Tests
| Test Parameter | Natural Gas (Btu/h) | LP-Gas (Btu/h) | Acceptance Criteria |
|---|---|---|---|
| Maximum Input Rating | 400,000 | 300,000 | ±5% of nameplate at rated pressure |
| Minimum Input (turn-down ratio) | — | — | Stable flame without lifting or flashback |
| Gas Supply Pressure (max.) | 14 in. w.c. (3.5 kPa) | 14 in. w.c. (3.5 kPa) | No malfunction or hazardous condition |
| Gas Supply Pressure (min.) | 5 in. w.c. (1.25 kPa) | 11 in. w.c. (2.74 kPa) | Flame stability and proper ignition |
| Flame Safeguard Response | — | — | Main gas valve closes within 90 seconds of flame loss |
| Over-Temperature Limit | — | — | Limit control stops burner before appliance exceeds rated temperature |
Table 1: Representative performance requirements common to conversion burners under ANSI Z21.17-1998.
Controls and Interlocks
The standard requires that conversion burners be equipped with:
- A primary flame safeguard that responds to loss of flame.
- A manual shutoff valve (not part of the burner but specified in the installation instructions).
- For LP-gas applications, a high-pressure regulator (if downstream of a tank regulator) to limit pressure to the burner.
- Limit controls (automatic or manual reset) to prevent overheating.
Implementation Highlights
Successful application of ANSI Z21.17-1998 in product design and field installation requires close attention to several critical areas.
Burner Sizing and Orifice Selection
The conversion burner must be matched to the appliance’s heat exchanger volume, draft characteristics, and clearance to combustibles. Manufacturers typically supply a range of orifice sizes and provide instructions for measuring input rate using gas meters. The standard mandates that the conversion kit include explicit instructions for input adjustment to within ±5% of the nameplate rating.
Air Shutter Adjustment
Proper primary air setting is vital for clean combustion. Too little air yields yellow tipping and soot; too much air can cause flame lifting or noise. The standard requires that the burner design allow a stable flame over the entire range of air shutter positions, with the adjustment mechanism secured after setting.
Best practice: Always perform a combustion analysis (CO₂, O₂, CO) after installing a conversion burner. The standard sets maximum CO limits of 200 ppm air-free for natural gas and 200 ppm for LP-gas in undiluted flue gas.
Retrofit Compatibility
Because conversion burners are installed in existing appliances—some of which may be decades old—the standard includes provisions for venting safety. The burner must be compatible with the appliance’s draft hood, flue gas spillage must remain within acceptable limits (per ANSI Z21.47 / CSA 2.22), and the ignition system must reliably light each port.
Tip: When converting from natural gas to LP-gas, the higher density of propane requires a smaller orifice and a larger primary air opening. The conversion kit must include both orifice and air shutter instructions specific to the target gas.
Compliance Notes
Compliance with ANSI Z21.17-1998 is typically verified through a third-party testing agency (e.g., CSA Group, UL, or Intertek). The standard is recognized as an American National Standard and is referenced by US states and Canadian provinces under adopted fuel gas codes.
Certification Marking
Each conversion burner must be permanently marked with:
- Manufacturer’s name or trademark.
- Model and serial number.
- Gas type(s) for which the burner is certified.
- Input rating(s) in Btu/h for each gas type at standard supply pressure.
- Date of manufacture (month/year).
Installation instructions must also include a statement that the conversion burner is to be installed by a qualified agency (usually a licensed gas fitter) in accordance with NFPA 54, CSA B149.1, or the local code.
Non-compliance risk: Using a conversion burner without proper certification voids the appliance’s original listing and may result in unsafe operation, insurance denial, or code violations. Always use components bearing the certification mark of a recognized body.
Field Inspection Considerations
Authorities having jurisdiction (AHJs) frequently check for:
- Presence of the conversion kit installation manual.
- Correct orifice sizing and input measurement.
- Adequate venting and spillage tests.
- Proper operation of all safety controls (e.g., flame rollout, limit switches).
The standard also requires that the burner’s installation instructions include a wiring diagram and troubleshooting guide. AHJs may reference ANSI Z21.17 to verify that the burner meets the minimum safety requirements regardless of the age of the host appliance.
Revision History
ANSI Z21.17-1998 was superseded in subsequent years by Z21.17-2003, Z21.17-2010, and later editions. However, the 1998 edition remains in use for older equipment and as a reference for retrofit projects. Users should confirm that the edition adopted by their local code is appropriate for the installation.
Q: Can I sell and install a conversion burner certified to ANSI Z21.17-1998 today?
A: Yes, provided the installation complies with the current adopted fuel gas code. Many jurisdictions allow products certified to earlier editions if they are intended to replace identical components in existing systems. Always verify with the local AHJ.
A: Yes, provided the installation complies with the current adopted fuel gas code. Many jurisdictions allow products certified to earlier editions if they are intended to replace identical components in existing systems. Always verify with the local AHJ.
Q: Does ANSI Z21.17-1998 cover conversion burners for outdoor barbecues or space heaters?
A: No. The standard is limited to burners for central heating appliances (furnaces, boilers, etc.). Outdoor cooking appliances are covered by other standards, such as ANSI Z21.58 / CSA 1.6.
A: No. The standard is limited to burners for central heating appliances (furnaces, boilers, etc.). Outdoor cooking appliances are covered by other standards, such as ANSI Z21.58 / CSA 1.6.
Q: What is the difference between ANSI Z21.17 and Z21.87 (Automatic Gas Ignition Systems)?
A: Z21.87 deals specifically with electronic ignition systems, whereas Z21.17 addresses the entire conversion burner assembly including ignition, but not the standalone ignition control.
A: Z21.87 deals specifically with electronic ignition systems, whereas Z21.17 addresses the entire conversion burner assembly including ignition, but not the standalone ignition control.
Q: Are there special requirements for conversion burners used in mobile homes or recreational vehicles?
A: Yes. ANSI Z21.17-1998 includes additional requirements for burners intended for manufactured housing, particularly for seismic anchoring and wind resistance of venting systems. Refer to Appendix B of the standard.
A: Yes. ANSI Z21.17-1998 includes additional requirements for burners intended for manufactured housing, particularly for seismic anchoring and wind resistance of venting systems. Refer to Appendix B of the standard.
Reference year: 2026