Propane: Treat It With Respect
Feb 04 '02
The Bottom Line Almost everything you didn't want to know about propane, and heaters we burn them in. Is it a liquid or a gas? Was it a prehistoric animal or plant? Yes.
This review falls under the category of "What should you know about Liquid Propane Heaters?" I want to start off by explaining, to those of you who didn't know already that propane is only in a "liquid" state when it is under pressure. It is liquified for storage and transportation, and it returns to it's true state as a gas the moment it is released from the pressurized tank.
In order to understand some of the following advice on what you should know about propane heaters, you should know the basic chemical differences between fuel gases we commonly use and where they all came from. Don't worry, I'll give you the condensed version.
Those who have read any of my previous reviews will appreciate that this is a category that I'm most comfortable in.
The Organic Theory
The most widely accepted theory on the origin of fuel gases is called the "Organic Theory", which suggest that unknown millions of years before we walked the planet, plants and animals either dead or almost dead were washed into basins of lakes and oceans all over the world. Over time these dead organic materials were covered over by sand.
Tremendous pressures generated heat which in turn triggered a chemical reaction, changing the once live materials into oil and gas. Pockets of which we tap into today, which were trapped in domes that were likely created by the changing crust of the planet. This is the condensed version of the "Organic Theory".
All of the following fuel gases are primarily composed of hydrocarbons or compounds of carbon (C) and hydrogen (H). The family of gases best known to you because you use them so often are, methane (called natural gas), propane and butane. All come from the same gas wells or domes created by our prehistoric friends.
Natural gas is primarily methane and is referred to as CH4 for one (1) atom of carbon and four (4) atoms of hydrogen.
Propane is C3H8 or three (3) atoms of carbon and eight (8) atoms of hydrogen.
Butane is C4H10 or four (4) atoms of carbon and ten (10) atoms of hydrogen.
So, in fact, you can see that all fuel gases are truly "natural gases", with important chemical differences. An increased number of carbon and hydrogen atoms will increase the density of a given gas, increasing the weight and the heating value. Unlike the manufactured gases of the old days, all of these natural gases are non-toxic and harmless if inhaled. So forget about sticking your head in the oven, unless you want to roast it.
Briefly, natural gas is approximately 6/10ths of the weight of air and will generate about 1,000 Btu's of heat per cubic foot burned. Propane is approximately 1.5 times heavier than an equal amount of air and will generate about 2,500 Btu's of heat per cubic foot. The butane in your Bic lighter is approximately 2 times heavier than an equal volume of air and will produce about 3,200 to 3,500 Btu's of heat.
So why the history and physics lessons? It helps some people to understand why there are dramatic differences between these fuels and some similarities.
Propane, as you know, has a higher density than natural gas (methane) and therefore a higher Btu heating value. All of this affects the size of the gas jet or burner orifice that the gas will be metered through in your heater. Much higher pressure is also needed to push the gas through the lines and through the burner orifice. Almost three times more pressure is used to deliver propane to a burner than is needed by natural gas (methane). Propane is generally set for 10" Water column (W.C.) manifold pressure or pressure after the gas valve versus natural gas which is generally only set for 3.5" w.c. manifold pressure.
While a 50,000 Btu per hour natural gas heater will require about 50 cubic feet of natural gas per hour, a propane heater of the same rating will only require about 20 cubic feet per hour to generate the same amount (50,000 Btu/H) of heat.
Therefore, we can shoot down a popular myth that propane heaters burn hotter than natural gas, since we regulate the flow of the gas to produce an equal amount of heat energy.
The Need for Proper Burner Adjustment: Avoiding Explosions
An explosion is highly unlikely in this day and age of controlled combustion and back up safety controls. It is generally a result of carelessness and abuse to a gas appliance.
All fuel gases need two additional things in order to burn, or explode, oxygen and heat. In simplistic terms, take away any one of these three ingredients, fuel, oxygen or heat and there will be no combustion. We deliver the propane from the tank via a gas line, the oxygen is contained in air and the source of heat is generally a pilot light, an electronic spark or an electric glowing rod (called hot surface ignitor).
All gas and air mixtures will not ignite or explode. Air normally contains an average of 20% oxygen and the rest is mostly nitrogen. In order for any fuel gas to burn or ignite there has to be more than 4% of gas mixed with air and less than 14 percentage of gas in the air. So in other words, a tiny leak which allows an air mix in the home of between 1 and 4% is too lean and insufficient fuel to ignite. In a larger leak if that mix is allowed to exceed 14% up to 100% gas to air in the home the mixture is too rich to ignite.
Having said that, I don't recommend standing around in a home that has had a major gas leak.
One of the uglier aspects of propane in this regard is it's inherent weight. Unlike it's cousin methane (natural gas) which rises and dissipates fairly quickly. The heavier propane gas leaks will pool like an invisible puddle and if the air flow around the leak is low, it will grow. If it finds a source of heat for ignition, it has a ready supply of oxygen, in the air above it to feed upon.
Both natural gas and propane, in their natural state are almost odorless and have odorants added to them by the gas distributors for safety. Mercaptan is one of the popular odorants added to give the fowl "gassy" smell most people associate with fuel gas.
With natural gas, even the smallest of gas leaks are usually quickly detected by a consumer's sense of smell, because again, natural gas rises quickly. Whereas, propane may be allowed to pool by the appliance and unless it is stirred up and distributed, the smell may not be detected early in a leak.
If you smell gas, even if the smell goes away, turn off the appliances, leave the building and call the gas distributor from a neighbors house, for an emergency service call. It's better to be safe than sorry and you should never treat a gas leak lightly. Obviously, this advice does not apply to gas cookstoves and ranges "that are being used" and may give off a bit of unburnt gas before they ignite. However, if the appliance is off and there is a gas smell in the room, have it checked.
A Gas Leak Is Not The Only Source Of An Explosion
If the appliance is running properly, the primary products of combustion are relatively harmless; heat, carbon dioxide and water vapor.
A properly set up gas heater will burn with a steady blue flame, with no flames lifting off of the burner. Ghosting or growing long, lazy and yellowish are indications of a lack of oxygen for complete combustion. With the slight exception of gas fireplaces, in which the air is reduced by design to produce a flame that resembles a wood fire.
If anyone can visually see the burner lifting off of the ports or turning slightly transparent (ghosting) or extinguishing and re-igniting itself, turn off the appliance and call in a licensed and competent service technician.
A serious lack of air/oxygen to any gas appliance will cause incomplete combustion. With incomplete combustion comes carbon monoxide, odorless, and colorless. Proper air ventilation to any room that houses a gas appliance is therefore extremely important.
A gas appliance that is lacking in ventilation air and suffering from incomplete combustion can on occasion allow a build up of unburnt gas to ignite. These cases are somewhat rare, but so happen. So pay attention to how a burner looks when it's operating.
In the course of improper servicing or neglecting to service some gas heaters, there is always the possibility of dirt plugging up burner ports around the pilot light or even dirt slowly building up in the pilot itself and cutting off the gas supply to the pilot flame. In such cases of weak pilot flames, the pilots are designed to shut down safely, which in turn closes the gas valve.
However, there are times when enough debris can prevent the pilot from quickly igniting the main burner. The result is a delayed ignition, which can range from a loud POP to an explosion.
Look at the pilot light, ensure it is strong and steady. If it appears very small, or if you are forced to relight it often, turn it off and call in a technician. Time the pilot by turning on the appliance and watching the flames ignite to all ports on the burner. It should not require more than four (4) seconds. If it does, can a service technician. Cleaning a pilot or changing a pilot orifice is not expensive.
This is particularly important with propane heaters, as a propane heater that does not ignite immediately from the pilot or ignitor may be pooling fuel in the bottom of the appliance. If any heater blows itself out you should always turn everything off and wait at least five minutes before trying to restart the pilot light. If it goes out again, wait another five minutes, before trying to relight it. On the third pilot outage call a technician to test it.
Natural Gas and Propane Generally Burn Cleanly.
Any time you find a large build up of soot in a gas appliance, it's an indication of poor/incomplete combustion. Propane gas heaters are more susceptible to producing soot, due to a lack of combustion air. However, there will sometimes be a little soot generated on the ignition of the appliance, which can accumulate inside over time. That's one of the main reasons for annual service contracts. Not the only concern though.
All gas appliances should be checked by a competent, licensed technician and by checked, I don't mean with a clipboard. They should come equipped with test equipment and cleaning equipment. They should visually check the burner performance, the gas pressures, the venting system for blockages or leaks, the circulation air fan for cleanliness (oil if needed), any air filters in the system should be cleaned or exchanged and the overall appliance checked for signs of wear, or leakage.
I always suggest finding a gas technician with a combustion analyzer, who knows how to use it. He/she should be able to run combustion tests on all appliances in the home and give you the results, including the efficiencies and carbon monoxide readings. A good technician will be able to give your appliance and the venting system attached, a clean bill of health and leave it operating according to the manufacturer's specifications.
People with propane heaters should have this done religiously, at least annually (just like I go to church every Christmas) but, the advice also applies to people with natural gas heaters.
I don't recommend unvented gas heaters of any description. I'm particularly disturbed by open flame propane space heaters that people seem to think are okay for heating up a cold room and literally drag in a propane cylinder and hook it up. These things may be okay for camping, but, not inside the tent. See unvented gas appliances for more rants on this topic.
At the end of the day, go to sleep knowing that your gas heater is well ventilated, your chimney or vent system is functioning, your flames are clean, your pilot is strong and your home is safe and warm.
Perhaps the next time your furnace or your heater kick on, you might want to give a little thanks to all of our prehistoric friends that made it possible.
Regards,
Gasman
(I'm burning another raptor tonight :-)
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