Propane Safety

Propane has been in use for quite some time, so its safety aspects are well-known and documented. The National Fire Protection Association (NFPA) has taken the lead in developing codes and standards for the safe use, transportation, and installation of propane and related systems. In particular, NFPA 58 “Liquified Petroleum Gas Code” provides the requirements for safeguarding all LP gas (propane) installations in homes, businesses, and industrial settings. It also addresses the safe transportation of propane. This code is meant to help designers, health and safety managers, authorities having jurisdiction (AHJs), and insurance professionals address the particular details and conditions for safe LP gas use.

Relatedly, NFPA 54/ANSI Z223.1 “National Fuel Gas Code” applies to all fuel gas systems, of all types (i.e., not just propane), in and around buildings. This code recognizes everything from the risk of carbon monoxide poisoning to the potential for fire and explosion. Updated regularly, this code offers the latest comprehensive provisions for the safe design, installation, operation, maintenance, purging, and inspection of gas piping, equipment, accessories, and appliances supplied with any type of fuel gas.

Note that NFPA 54 is not the same as the International Fuel Gas Code (IFGC) prepared and issued by the International Code Council (ICC). This code similarly addresses the full range of fuel gases and all of the related system components. The IFGC does reference provisions from NFPA 58 specifically for propane systems but does not reference NFPA 54. Therefore, it can be important to verify which fuel gas code has been adopted in a given jurisdiction, either NFPA 54 or the IFGC. In either case, NFPA should be followed whenever the specifics of propane systems need to be addressed for safety and may also be adopted by a local jurisdiction.

Using Propane in Buildings

Keeping in mind all of the foregoing, propane can readily be used in buildings either as a stand-alone fuel source or as part of a hybrid energy strategy. It has been routinely used as a stand-alone solution, particularly in locations that either don’t have natural gas available (i.e. rural or edges of metropolitan areas). Of late, it has also been used where natural gas usage is being restricted by local regulations for environmental protection and/or in the interest of reducing fossil fuel use. In both of those cases, propane can help serve these locations with cleaner solutions for space heating, hot water production, cooking, or other residential and commercial uses.

When propane is used as part of a hybrid system, it can allow the building’s electrical system to be more appropriately sized and reduce upfront costs. In a residential or small commercial building, that could mean, for example, downsizing from a 400-amp electrical service to a 200-amp service. Hence, an on-site solar electric system may be able to provide most, or all of the remainder of the energy needs of the building. In addition to these energy aspects, on-site propane-based hybrid systems can increase resiliency by allowing building systems to keep running during power outages from the grid, especially if propane back-up generators are utilized.

CENTRAL HEATING SYSTEMS

Propane has been used for decades to fuel central heating systems in residential and light commercial buildings. When the focus is on moving heated air, propane-powered furnaces provide warm air at the discharge registers at a higher temperature providing the feeling of a quick warming effect. Condensing furnaces achieve high efficiency, take up less space than older systems, and require simpler flue and dedicated air intake. Hydronic radiant heating systems can alternatively be used to pump hot water from a propane boiler through in-floor or perimeter tubing systems, keeping the warmest air on the floor. The nature of this type of system is to heat the interior spaces evenly but more slowly than an air-based system. In some cases, the heating load may be small enough that the hydronic system is based on a smaller water heater or even a tankless water heater system. Larger spaces and buildings will rely on a more conventional or compact, high-efficiency boiler. Regardless of the specifics, any of these conventional systems are controlled by a thermostat to introduce the appropriate amount of heat when needed. While these systems are well-known and widely used, they are also being paired with electric heat pumps to create a hybrid solution.

Hybrid Heat Pump Systems

Air source electric heat pumps or so-called “split systems” are a popular source for home heating, particularly since they can readily provide heating and cooling in the same system. This makes them very appealing in warm climate zones, but they can encounter challenges in mixed and colder climates. While heat pump technology has been steadily improving in recent years, there are still limits requiring a heat pump system to turn on emergency or auxiliary heating. This is usually in the form of electric resistance heat that is very energy intensive and much less efficient than the regular heat pump operation. Even before the auxiliary heat kicks in, heat pumps can have comfort challenges, supplying air that feels cool.

Hybrid systems are designed to solve these challenges with the help of a propane back-up system. That back-up could be a conventional furnace providing heated air or a boiler providing heated water to a separate radiant system. A recent innovation is to use a propane-powered tankless water heater that is attached to a heat pump to replace the electric resistance back-up heating. This is accomplished by the use of a hydronic coil custom fit to match a heat pump air handler plus a circulating pump and a control module. The pump moves hot water from the tankless water heater to the hydronic coil, then the heat pump air handler fan blows air across the hydronic coil to heat the home. A hydronic air handler also provides a less extreme heat to help avoid stratification, in which the air close to a duct is much warmer than space farther away.

When the thermostat calls for auxiliary or emergency heat, the hydronic-based pump and tankless water heater come on instead of the heat strips. In this way, the air handler module communicates to a propane tankless water heater to circulate hot water through a hydronic coil that has been installed at the air handler. The results of this type of system include: 1) improved comfort since hybrid heat pump solutions can deliver heat faster and more consistently than all electric systems; 2) greater affordability compared to all-electric systems - hybrid heat pump solutions are cheaper to run than all electric systems using electric resistance back-up heating. They have been shown to reduce operating costs by up to 35 percent; 3) increase efficiency since hybrid heat pump solutions are energy efficient, requiring less electricity use and less overall energy consumption while still improving heating performance; and 4) design flexibility for architects and owners considering additions of solar- or wind-generated power. A hybrid heat pump solution can make installation more cost-effective due to the reduced electrical peak and running loads. All of these results will vary, of course, based on the particular details of a building’s location and design and should be reviewed and assessed accordingly.

In addition to the foregoing, when compared with a gas furnace, tankless hydronic heating offers the opportunity to use only one gas appliance that can provide both heat and domestic hot water. That means fewer vents and gas connections to install. It also allows a home to leverage the thermal efficiency of a tankless water heater, which can achieve efficiency levels of around 94 percent.

EFFICIENT PROPANE HOT WATER SYSTEMS

Propane can be an efficient means to produce hot water in many residential and small commercial settings. In addition to hybrid heating and domestic hot water systems, propane can also be used in a stand-alone domestic hot water system in either of two common ways:

Propane-tank-type water heaters This option has been commonly used to heat water using a gas burner instead of an electric heating element. Typically, propane tank water heaters can use the same connections, space, and venting as natural gas models. Of most interest to homeowners, propane heats water twice as fast as electricity and can cost up to a third less to operate over time.

Tankless water heaters This type of on-demand water heater avoids storing and reheating hot water by eliminating the tank. They operate by quickly heating water in a coil over high-output propane burners, then immediately circulating the heated water through the piping to the plumbing fixtures where it is being called for. By heating water only when needed in this way, it can reduce energy usage by up to 50 percent in some cases. That means the initial investment for a tankless propane water heater is typically offset within three years through lower operating costs. The cost is further reduced in many states that offer a rebate on the installation of propane appliances and by federal tax credits that are available for the installation of most propane tankless water heaters.

Photo courtesy of Propane Education & Research Council

Tankless hot water systems powered by propane can be more efficient and better suited to many residential designs compared to tank-type water heaters.

Tankless propane water heaters typically last for 20 years or more while tank-type water heaters are known to have a comparatively shorter expected useful life. Relatedly, a tankless propane water heater frees up 93 percent of the space used by a tank-type water heater. Finally, propane tankless water heaters provide an endless supply of hot water that is not restricted by tank capacity. Locating the tankless heater close to the fixtures requiring hot water can also reduce water usage where owners or occupants are “waiting for the hot water to reach the fixture.”

When looking at domestic hot water systems, the best results can be obtained by considering all available options, reviewing propane piping requirements, and verifying the needed controls for the solution selected.