Conversions of gas appliances to either natural gas or propane involves the changing of internal parts to properly compensate for the differing pressures between the two. Appliances fueled by either natural gas or propane can be converted to run on the other provided an approved conversion kit is available.
Making changes to an appliance so that it can utilize a different fuel is known as appliance conversion and involves the replacement of gas orifices, burners and/or appliance regulators. These internal connections and gas utilization fittings are designed to work with a particular gas that has a specific pressure. Natural gas is a much lower pressure gas than propane and converting the appliance to one or the other gases requires that the differing pressure is compensated for. In other words, connecting a natural gas appliance to a propane piping system will result in appliance malfunction and possibly danger. The reason for this is because natural gas orifices are larger than propane orifices strictly because of gas service pressure. In this case, the higher pressure gas flowing through a larger orifice will result in more gas through the burner and likely, more flame...an unnecessarily large flame. Conversely, trying to use a propane appliance with natural gas will likely result in a very small flame or no burner flame at all because of the lower pressure gas and the smaller orifice. This is the underlying purpose of an appliance conversion from propane to natural gas or from natural gas to propane. Additionally, appliances cannot be converted from electricity to propane, or vice-versa.
Appliances can be converted only if they are listed as such or can be safely converted by a licensed gas/appliance technician. Most appliances available today are designed to use only one fuel such as propane or natural gas (as pictured below).
As mentioned in the above warning label picture, the rating plate should be checked for the type of gas the appliance is designed for. Gas appliances that are purchased through a retailer will be labeled as such for use with either natural gas or LP Gas. Appliances designed for use with propane will often be labeled "LP" while "NAT" indicates natural gas. Water heaters, ovens, ranges and heaters that are able to be converted to one gas from the other are labeled accordingly and will most likely come with a conversion kit in the appliance packaging. However, appliance conversions and conversion kits are increasingly being limited to stoves purchased as new. Also, if the appliance is able to be converted for use with another fuel (LPG or natural gas), the packaging should clearly say so.
The conversion of any gas appliance to another fuel involves not only replacing the orifices (fixed and pilot), but the replacement of appliance regulators, burners and possibly the venting as well. Appliance conversions these days are not as simple and straightforward as they used to be, if the appliances are able to be converted at all. Historically, most all appliances could be converted from natural gas to propane and vice-versa but the the gas appliances manufactured today are engineered (by professional engineers) to be used with one type of fuel as specified by the manufacturer for dedicated fuel use. In other words, most all gas appliances are built to use either propane or natural gas and are not designed to be converted or modified for use with another fuel.
The topic of converting appliances has been a problematic issue for the propane industry because of the "do it yourself" consumers who believe that switching or drilling out an orifice constitutes an appliance conversion. If an appliance is to be converted for use with another gas (natural or LP), then several other factors must be addressed including:
In truth, it would be cheaper to buy a new appliance than to try and properly convert one that is designed for use with either propane or natural gas. Even if appliance conversion kits are available for certain equipment, the conversion should be handled by licensed technicians so that all necessary adjustments can be made prior to placing the converted appliance into operation.