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Gas Conversion Orifice Sizing: A Safety-First Kit Selection Guide

Posted by Joseph Moore on

What size orifice do I need to convert propane to natural gas?

There is no single safe orifice size for every appliance. The correct specification must come from the appliance manufacturer's conversion instructions for the exact model, gas type, input rating, pressure, and installation conditions. A kit for natural gas to propane is not a substitute for a propane-to-natural-gas kit.

Safety disclaimer: This guide is a purchasing and identification checklist, not installation instructions or a drill-size chart. Incorrect gas conversion can cause fire, explosion, carbon monoxide poisoning, serious injury, or death. Have conversion eligibility, kit selection, installation, and commissioning confirmed by a qualified, licensed gas-appliance technician authorized for the equipment and work required in your area. Not every appliance is convertible. A product listing does not establish manufacturer approval for your appliance.

1. Start with the appliance nameplate

Before ordering, photograph the complete nameplate and any existing conversion label. Record the manufacturer, full model and serial number, listed gas type, input rating in BTU/h, and any listed inlet or manifold pressure. Photograph the gas valve identification label too, if it is accessible without disassembly. Do not remove covers or disturb gas connections to collect this information.

Keep the units and wording exactly as printed. If the plate gives a total appliance input, do not treat it as the input of each burner. If the nameplate and a conversion label disagree, or either is unreadable, stop and ask the manufacturer or technician to identify the appliance's approved configuration.

2. Match the exact kit, not just the number of burners

Give your technician or parts supplier the nameplate photos, the current fuel, the intended fuel, burner count, gas valve make and model, and installation altitude. Ask them to confirm the exact conversion kit and applicable manufacturer instructions before purchase.

Burner count is a cross-check, not proof of compatibility. Three-burner appliances can use different inputs, valves, pilots, regulators, and orifice designs. Have the technician compare the documented appliance and burner input ratings with the manufacturer's conversion specification. Do not divide total BTU/h by burner count to select an orifice unless the manufacturer's instructions explicitly establish that method for that appliance.

Check the complete required parts list. Depending on the appliance, conversion can involve main burner orifices, a pilot orifice, gas valve conversion components, an appliance regulator, other components, and conversion labeling. Changing the main orifices alone does not establish that a conversion is complete.

3. Verified store listings to compare

These links identify products listed in our store. They are starting points for an exact-model compatibility check, not blanket approval to convert an appliance. We have not verified an orifice diameter, input-rating range, or permission to drill from these listings.

4. Pre-drilled orifices versus drilling

When the manufacturer's instructions specify supplied, factory-sized replacement orifices, those exact specified parts are required. Do not enlarge them to compensate for a suspected pressure problem or use a generic online drill chart as a substitute. For example, Southern Pride's gas-conversion bulletin expressly prohibits field drilling for the equipment covered by that bulletin; Henny Penny conversion instructions specify replacing burner and pilot orifices with the kit's supplied parts. These examples do not establish compatibility with the kits linked above.

Only consider a kit that requires field sizing if the appliance manufacturer explicitly authorizes that procedure for the exact appliance and kit, supplies the applicable specification, and a qualified technician accepts the work. None of the linked store descriptions establishes permission to drill. If the instructions are missing, the supplied parts differ from the documented specification, or someone proposes a guessed drill size, stop and obtain the correct instructions and parts. This guide deliberately provides no drilling procedure or universal orifice diameter.

5. When to stop and call a licensed technician

  • The manufacturer does not confirm that the exact appliance can be converted to the intended fuel.
  • The nameplate, conversion history, model, input rating, or gas valve identification is missing or inconsistent.
  • The kit's conversion direction, burner count, valve components, or model applicability does not match.
  • A supplier cannot confirm the required orifice specification or the manufacturer's conversion instructions.
  • The work would require drilling, pressure adjustment, opening gas connections, or commissioning. These are technician tasks, not steps to attempt from this buying guide.

Have the technician perform the manufacturer's required checks and testing before the appliance is returned to service, including applicable gas-tightness, pressure, input, ignition, combustion, and safety-control checks, and apply the required conversion labeling. Do not test a questionable conversion by operating the appliance.

What to send us before ordering

Send a clear nameplate photo, full model and serial number, gas valve identification, burner count, current fuel, intended fuel, and the kit number you are considering. Include any existing conversion label and the manufacturer's conversion documentation if available. Ask for an exact-match review, not a universal drill size. Have your technician confirm manufacturer authorization and installation requirements before purchase.

Safety references

Manufacturer instructions are appliance-specific. The following explain the safety principles cited here and are not installation instructions for every appliance or for the linked kits:

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