Bring on the Heat!

One day, years AGO, I was waiting for my girlfriend to get home when I decided I would brew some beer. I have always been an all-grain brewer, but back then I heated water in all of the pans I had, mashed in a plastic bucket and boiled on the stove.

This particular brew went like most brews for me. Everything was fine until it came time to boil. Since I didn’t have a six-gallon kettle I had to spread my boil across the stove. I had to divide my hops by three and watch three boils. Since all three pots were different sizes, it was quite a challenge.

You can guess what happened: Right when all three pots were boiling over and syrupy wort was running down the front of the stove, my girlfriend walked in. If it had been my house, I would have gotten away with it, but I was in her apartment. She hit the ceiling and forbade me to brew inside.

The next weekend I bought my first outdoor cooker from a local homebrew shop. Since I was helping out at a nearby microbrewery, the master brewer gave me two kegs. I cut the lid out of one for a boil kettle and had a coupler welded in the side so I could install a ball valve. I borrowed a friend’s propane tank and I was back brewing.

That was the best thing that ever happened to my brewing. I saved about 30 minutes per brew, I had much more control over my final gravity and volume and I could hose down the deck when I was done. My girlfriend was satisfied. (She was never happy with me brewing, though, so satisfied was as good as it got. Next girlfriend…)

I think a large boil kettle and an outdoor cooker is the best investment any homebrewer can make. The two arguments I can make are social harmony and brewing quality. There are many designs available and I hope to clear up some of the confusion. But before we can decide on the best burner for you, we need to decide what gas you are going to use.

Propane and Natural Gas:

Two gases are widely used for homebrewing: propane and natural gas. The most common is propane, a product of refined petroleum. It is usually purchased in small cylinders at RV stops, gas stations and gas companies (look under “gas-propane” in the phone book). It’s sometimes trucked into large tanks to heat peoples’ homes. (If you have a propane tank the size of a small car in your backyard, you’ve probably noticed it by now.) When put under enough pressure, propane turns into a liquid. This liquid is sometimes sold by weight (pounds) and sometimes by volume (gallons).

You can purchase or exchange your small propane tank. Since the propane tanks require Department of Transportation (DOT) safety certification every few years, many people choose to rent or exchange theirs. If your tank has passed your DOT certification date, it needs to be pressure-tested before it can be filled. It usually is cheaper to purchase another tank, rather than having one re-certified. If you choose to exchange, you simply purchase a tank. Whenever it gets empty, you swap it for a full one.

The main advantages of propane are that it’s easily transported, commonly available and can be supplied in high pressures. A regulator is used to lower the pressure of the gas from the super-high pressure in the tank to a pressure that can be used. The higher the pressure, the more gas will flow from a given jet size at a higher velocity. That translates into more gas burning. At a certain point, the velocity gets so high that the flame blows itself out. Just before this happens, the flame starts to “tear off” the jet.

Affordable regulators are available up to ten pounds per square inch. Regulators are also available in very low pressures, as low as 11 inches of “water column” or 0.40 psi. Water column is another method of measuring pressure; it’s widely used in the gas industry and comes in handy when designing gas-control systems. Water column is often used when very low pressures are involved; in basic terms, it measures how high a given amount of pressure will push a column of water. One psi equals 27.7 inches of water column.

Natural gas is a combination of  gases that are extracted from a well in a field. Depending on the field, the properties can be very different. It is supplied to many homes by a pipeline in gas form at very low pressures (less than 0.5 PSI). If your house is one of these, you probably know it.

The main advantage of natural gas is that it can be piped into your home if you are lucky enough to live in a delivery area. And  you can use off-the-shelf water heater parts to make a custom-designed gas system.

When we burn gas, we get heat by tearing off the carbon molecules and adding oxygen (in the form of air) to make carbon dioxide and water. We also get a little carbon monoxide (CO), hopefully not much since it is a poison, plus some partially unburned gas molecules called hydrocarbons and various NOx (oxides of nitrogen) compounds. The reaction is exothermic, which means we get more heat out than we put in to get it started.  In an ideal propane burn, we start with one molecule of C3H8 (propane) and 5 molecules of O2 (oxygen) and end up with 3 molecules of CO2 (carbon dioxide) and 4 molecules of H20 (water). Or in chemical notation:

C3H8 + 5 O2 = 3 CO2 + 4 H2O + heat  

“What?” you say. “I have never seen little streams of water coming from my burner!” That’s because pure steam is an invisible gas. The “steam” you see coming from boiling water is actually droplets of water re-condensing after hitting the cold air. (You probably don’t notice the 7 gallons of water coming out of the exhaust pipe for every gallon of gasoline you burn, either!)

The heat output of a gas is measured in BTU (actually, BTU/hr is the technical specification, but it is commonly written as BTU). Anyone who has looked in a brewing catalog has seen BTUs, but what are they? A quick look into the reference library reveals that BTU means “the quantity of heat that must be added to one avoirdupois pound of pure water to raise its temperature from 58.5° F to 59.5° F under standard pressure.” (Avoirdupois pound is the proper name for the pound with which we are familiar). In plain English, that means if you take a pint of water on a cool day at sea level and add one BTU, it will go up one degree Fahrenheit in temperature.

Propane and natural gas have very different properties. Propane has more energy per cubic foot than natural gas. Therefore, propane jets are much smaller than natural gas jets.

Choosing between indoor and outdoor use often determines the choice of natural gas or propane. While it is true that natural gas is easier to burn completely and should be safer when used indoors, it is a mistake to move your converted outdoor cooker indoors. It is illegal for any manufacturer, in fact, to make an unvented burner over 5,000 BTU for indoor use.

The proper methods for designing an indoor brewery are beyond the scope of this article. Briefly, you need to vent all exhaust gases through a properly designed hood or build a combustion chamber around your burner and vent all gases through a flue. I would also install a carbon-dioxide meter but I question their reliability.

An outdoor cooker has three main features: the burner, the stand and the regulator. The heart of any cooker is the burner.

Five Common Burners:

Burners are available from a variety of sources. When a manufacturer is looking for burners for a cooker, they usually use an existing casting instead of designing their own. Here is a summary of the common burner castings used by most outdoor cookers.

High-pressure burner: This is the burner style in the popular Camp Chef SH-140L. It is two pieces held together with a bolt in the middle. It has an  adjustable air inlet, which provides the ability to have a large or small flame and maintain efficiency. (Air provides the oxygen that makes the flame possible, but you need the right ratio of propane to oxygen molecules. If the mix is too lean — not enough oxygen—  there’s no flame. If the mix is too rich, you produce too much carbon in the form of soot.)

The high-pressure burner has lots of power for big boils and can do a 20-gallon boil. It runs well at 15 psi and below. Above 15 psi, it is difficult to get enough air and the flame starts to “tear off the burner” or sputter out. The new regulators are limited to 10 psi, but this burner still puts out plenty of heat. It fills up with sugar when you boil over and can be a challenge to disassemble after years of use. I would describe the flame pattern as medium wide and the sound level as medium. They can’t be converted to natural gas.

Ring burner: This is a cast-iron ring with a bunch of little holes in concentric rings around the burner. It has an adjustable air inlet. It runs better at lower pressures than the high-pressure burner, making it useful for smaller boil volumes. It has a very controllable flame and spreads the heat out to a large surface area. This is probably the most wind-sensitive design. Most outdoor cookers that use this burner provide a piece of sheet metal about 4 to 6 inches high that goes around the burner and is designed into the stand to provide some wind protection. With a 10 psi regulator, they can do a 10-gallon boil. I have seen these converted to natural gas, but at household pressures they are barely suitable for a 5-gallon boil.

Jet burners: This burner is a square tube with a gas jet inside. It relies on creating a large amount of airflow from bottom to top while burning. It is not very efficient, because the air does not mix very well with the gas,  and it is very powerful, so it uses lots of propane. They are very loud and have been described as sounding like a 747. Because the flame pattern is so small, some people have had problems with scorching wort. There used to be a conversion kit available for natural gas but I was unable to find one.

Multi-jet burners: These put out more heat than any other standard homebrew burner. The flame is spread out very well and they are the quietest burner I have found. You probably have seen these lately — they are a ring with a bunch of brass jets. Each jet has an orifice and four air inlet holes and is a burner all its own.

The best ones are made by Solarflo and  are available in size ranges from about 20,000 BTU to about 2,000,000 BTU. They have a wide range of options, like flame height and choices of gases and pressures. The Solarflo burners are mostly used by commercial establishments and are very difficult to get for home use.

The ones available to the homebrewer are Asian knockoffs and are available only in one size. The quality is not anywhere near the Solarflo burners, but they are 1/7 the price (about $50). I have not seen one with a stand yet, but I am sure one will be available soon. If you want to use one now you will have to design and weld your own stand.

The main advantages are they have no air adjustments, they have a very large output and they run very well on low pressure (less than 0.5 psi). Gas controls for propane are designed to work at very low pressures, so this becomes one of the only options for electronically controlling your hot liquor temperature.

Multi-jets are the most expensive burners. They are available in natural gas or propane. They are jetted for commercial natural gas pressures, but will burn very well at residential pressures. The output is about 25 percent lower, however. Some people find these burners too powerful for homebrewing and the output can be lowered by replacing some of the jets with bolts and copper washers.

Venturi burners: This is the burner used in the common Bayou brand of cookers. I have not used one of these burners, so I am only mentioning them for completeness. I expect them to be similar to the jet burners,  but with better efficiency.

The Stand:

If the burner is the heart, the stand is the soul. If you have ever tried to put a keg on a ring, tried to siphon wort upward or had to lift 5 gallons of boiling wort, you will understand why choosing the right stand is important. As a rule, the more legs a stand has, the more stable it will be. If you use or ever plan to use a converted Sankey keg for a brew kettle, I would avoid the ring-shaped stands, as the keg can rock on the ring.

Carefully plan your transfer out of the boil kettle. Depending on what vessel you’re using next, the height of your stand can be very important. A good brewing stand should be taller than your carboy. If you brew in the wind, a windshield not only protects the flame but helps air flow.

The last thing to consider is the finish. Stands are available in black paint, black high-temperature paint and stainless steel. The cheapest stands have paint that burns off the first time you use it and makes a very bad smell. The stand then starts to rust. Stainless is expensive but is the easiest to maintain. High-temp paint is the best compromise between cost and durability.

The Regulator:

Most, if not all, outdoor cookers are supplied with a regulator, so this is a no-brain decision. If you end up having to buy your own there a few things to consider. The first is size. If you are only going to run one burner, then the smallest regulators are suitable, but when you start running three multi-jet burners, a larger regulator becomes necessary. Regulator manufacturers are reluctant to supply BTU capacities for their cheapest regulators, so you are on your own to figure out the capacity of your regulator.

The second thing to consider is pressure. Propane regulators used to be available adjustable from 0 to 18 psi. As of this writing, the 18 psi regulators are no longer available and the replacement is 10 psi. There is a rumor in the industry that these will be replaced with a lower pressure as well. Low pressure regulators are usually set to about 0.43 psi.

The last thing to consider is the connection to the tank. Recently tank manufacturers have begun to change the thread on propane tanks. The old tanks have a female left-hand thread that is much like a bolt thread. The new tanks have a male square thread like an ACME thread. I am told it is an effort to keep people from cross-threading them (getting the fitting out of line) and creating a gas leak. Soon all propane tanks and regulators will be the new style.

How to use your cooker:  

So you made the plunge and bought a burner. Now you are wondering, “how do I use this thing?”

All you have to do is light it, right? Well, sort of. Don’t forget to connect the regulator to the tank. This is pretty simple; don’t cross-thread it, leave it loose or tighten it too much. Just past snug is usually good. If you think you might have a leak, spray soapy water on the union and look for bubbles.

Next you get to light the burner without getting burned. The trick here is to light the match or lighter before turning on the gas. (I recommend the long butane lighters.) When the flame is in place, turn on the gas and keep your hair out of the way. The burner should light right up. If it does not, turn off the gas until you figure out what the problem is. If you have an adjustable regulator, make sure it is adjusted to high pressure (all the way in).

Once you have a flame, your next goal is to adjust it. This is easy to do, unless you are pushing the limits of the burner. I pick the setting I think I need, then I close off the air and adjust up until the yellow flame disappears. If you practice this, you can set the flame higher and lower than the average brewer. When I need a different heat setting I adjust the gas, then the air.

Caring for your burner is fairly easy until you boil over. Then it is easiest to clean it right away. Once I heated up my high-pressure burner and turned it upside down. A few ounces of syrup poured out!

When you get your regulator, it has a cap on the gas end. If you save this and reinstall it every time you disconnect the tank your regulator will last longer. Dust and moisture are bad for regulators. Also, there is a small hole on the front of the regulator that cannot get plugged. If you spill on your regulator it is very important to check to see if the hole is clean. Do not put a pin in and puncture the diaphragm!

If you want to tweak your burner, it can be done. The limiting factor in burner design is the burner’s ability to mix gas and air. If the mixing is done internally, you can polish all of the casting flash out of the air passage to get more air. If you do this carefully, you can bump up the pressure or jet size a little more. If you make the jet size larger, more gas can flow through at the same pressure. At some point you are unable to get enough oxygen and you only make soot.

Multi-jet burners are more efficient if you separate all of the air from the top and bottom with a large donut. It should be made from steel sheet metal and have an inner diameter slightly larger than the burner and an outer diameter the size of your kettle. While you are fabricating the ring, you may as well tie it into a wind screen about 4 inches high that extends above the donut. This will make all of the air come up through the center. It is important to eliminate any air coming from the sides of a multi-jet burner to maximize efficiency.

If you keep your burner clean and the significant other happy, you will have a long and happy life brewing on your outdoor cooker.

Issue: November 2001