Bring the Heat
Ever since I started homebrewing in the early ‘90s, heating water quickly has been a challenge. A watched pot truly never boils. Until you walk away. Then it makes a colossal mess and gets you permanently banned from the kitchen. If you’re like most brewers, you take on your first batch with a stovetop extract batch using a kettle that isn’t big enough for boiling all the wort at once. Residential stoves are great for the 1- to 2-gallon (4- to 8-L) batch sizes, but they just aren’t powerful enough to boil much more than 2 or 3 gallons (8 or 11 L) of water. To accommodate doing larger 5-gallon (19-L) batches on a stovetop, with a smaller volume kettle, a concentrated wort boil is the typical solution. This is done by adding water in the fermenter to dilute the wort to your desired original gravity. That’s how I started brewing, as have many brewers over the years. But I quickly wanted to do larger 10-gallon (38-L) batches, and also wanted to dive into all-grain brewing. And that is where the heat source dilemma first reared its ugly head.
There are basically two types of energy readily available: Fuels such as propane and natural gas, and electricity. In this article I’ll discuss the pros and cons of each, and how to properly and safely use each type of energy. While electric brewing is becoming more common, particularly with the all-in-one brewing equipment becoming available, propane is still the most common.
Propane and Natural Gas
Other than the obvious chemical differences between these two fuels — natural gas, which is mostly methane (CH4), and propane (C3H8) — there are several important physical and thermal differences. Natural gas is pumped to your home in gaseous form, and for safety reasons, at a fairly low pressure — usually less than 10 inches (25 cm) of water column (0.36 PSI, 2500 Pa). Propane, on the other hand, is available only in bottled form, typically 20- to 40-lb. steel pressurized canisters. Note that the propane is in liquid form inside the tank as it is at about 120 PSI at room temperature. The regulator on your propane tank will reduce that pressure typically from 1–10 PSI; many more times more pressure than that of residential natural gas.
The other main difference is that methane has less energy per cubic foot of fuel than does propane. Couple that with the low pressure available for natural gas and the result is that propane burners are capable of much higher ratings than the same burner run on natural gas. That’s why propane burners remain the most common for homebrewing. They put out a lot of power for a relatively low price, are quite portable, and are more than adequate for even large batches.
There are a couple cons to using propane. The first is refilling tanks — you’ll get about 3–5 batches out of a 20-lb. tank of propane, so the cost is around $4–5 per batch. The second is inadvertently running out of fuel mid-batch (been there) is frustrating. So always have a spare tank on hand or make sure your tank is full before brew day.
Sizing for a gas burner is fairly straightforward. If you’re doing 5-gallon (19-L) batches, you’ll want about 30,000–50,000 BTU/hour rating. For 10-gallon (38-L) batches you’ll want about 50,000–70,000 BTU/hour for a reasonable heating time. A BTU (British Thermal Unit) is a measure of heat energy. The measure for burner power is BTUs consumed per hour (BTU/hr). That rating is the total heat output of the burner at the maximum rating. Measuring the actual output of a burner is quite simple if you have a scale that is accurate to about 0.1 lb. (0.5 kg) and can weigh up to about 30–40 lbs. (13–18 kg). Simply weigh the propane tank before lighting your burner, and then run the burner at full power for one hour. Weigh the tank again to measure the amount of fuel burned (starting weight – ending weight). Make sure you remove the regulator hose for each weighing so that it doesn’t influence the measurement. Multiply this by the heat energy in 1 lb. of propane (21,700 BTU/lb.). For example, if your burner burns 1.5 lbs. of fuel in one hour, the rating is 1.5 X 21,700 = 32,550 BTU/hr.
From my experience, many published ratings are overstated, so don’t always believe what is printed on the box. Doing a search online for other brewers’ experience with a particular model, or reaching out to your local homebrew retailer is highly advised. One important thing to note is that the max rating is not the actual energy you’re putting into your water! Only about 30–45% of that energy ends up being transferred through your kettle into your water! The remainder ends up heating the atmosphere. That leads to the next con of propane burners — ventilation. It is highly recommended to only use burners in an outdoor space. Not only will the heat build up in an enclosed room, but so will the fumes potentially leading to asphyxiation and carbon monoxide poisoning. I wrote an article in the January-February 2017 issue of Brew Your Own for properly ventilating indoor brewing rooms for safe operation. However, if outdoor brewing doesn’t work for you, natural gas is a much better choice for indoor use for safety and also convenience. Plus, natural gas is cheaper and is pumped to your house! I’ll talk about converting burners for natural gas use in a bit.
While some brewers use multi-jet type “wok” burners due to their high output, I don’t generally recommend them for homebrewing as they are not as adjustable as the traditional burners (many yellow flame at lower settings and blacken the bottoms of the kettles) and they are quite noisy. For very large kettles, 50-gallon (190-L) and larger, they are more common due to their high output potential. There are also “turkey fryer” burners that use a simple “cup” burner. They are very inexpensive and put out a reasonable amount of heat. But they are quite noisy and not very efficient.
Anatomy of a Burner
Figure 1 shows the elements common to nearly all propane burners in the market today, although some will look different on different burner designs. Let’s take a closer look at what each part does.
Venturi – This is the long neck where the fuel is mixed with a portion of the air needed for combustion. The mixture inside the venturi is too rich to burn. If you get too much air, you can get a back-lighting condition where the fuel burns inside of the venturi. This emits a growling sound. It is never advised to run any burner in this condition. Always assemble the burner according to the manufacturer’s instructions. When the fuel exits the nozzles on the top of the burner, additional air is available for combustion. While some venturis are straight, most have a hyperbolic curve to them, much like cooling towers you see at electrical power plants. This shape allows air to be drawn in more efficiently from the jet of fuel that passes through
the inlet.
Orifice – This is a brass fitting with a small hole at one end. This hole (orifice) controls the fuel delivery and creates a jet of fuel into the venturi. The hole diameter is tuned specifically for each burner for proper burn quality, so they are not interchangeable with other burners. The other end of the fitting is connected to the fuel hose leading to the tank, and may also have an adjustment valve affixed to it.
Damper – The damper controls the amount of air allowed into the venturi. The more open it is, the more air it draws in. Some burners require the damper to be adjusted to achieve the correct burn. Others use a fixed damper position.
Nozzles – Burner nozzles are where the fuel is mixed with more air and begins to burn.
Body – The body and frame of a burner not only supports your kettle and the burner itself, it also controls the flow of air to the outside of the burner and directs the heat energy onto the bottom of your kettle. In addition, the burner ring can shield wind gusts you’ll experience brewing outdoors. Most are painted steel. The more premium material is stainless steel, which stays nice looking for years and will last for a very long time. If you’re using a painted burner for the first time, expect some burning, fumes, and discoloration for the first few uses. I highly recommend a “burn-off” for an hour with no kettle on it for the first 30 minutes, and then with a full kettle on for the next half hour. Any char on the bottom of the kettle can be scrubbed off with Bar Keepers Friend. After that you shouldn’t get too much more fumes from the paint.
Burner Adjustments
Adjusting a burner is fairly simple, but also very important to do. It is important to adjust the fuel and air flow using the damper for the most efficient burn. Ideally, the flame is pale blue and never lifts off of the nozzles. It will burn very quietly. This is the most fuel-efficient mode for operation and the best for transferring the heat to the water, not the great outdoors.
If the flame begins to lift off of the nozzles and becomes a brighter blue, there is too much air and fuel for the nozzle to effectively burn. You’ll also hear a grumbling from the flame. To correct this, simply restrict the air flow using the damper. You may also need to reduce the fuel flow using the valve. Note that some regulators come with a fuel control knob that serves this function. While it is possible to continue adding fuel and air to increase the power and heating rate, it does create more combustion pollutants (NOx), which tends to make your eyes itch. In addition, the transfer efficiency of the fuel to your water is decreased. It also burns a lot of fuel.
If at any time you see yellow flames, the fuel doesn’t have enough air to burn and you’ll need to open the damper to let more in. The drawback with yellow flames is that they aren’t very hot, and they soot the bottom of your kettle with black carbon that is annoying to remove. Also note that if the flames are reaching up the side of your kettle you’ll want to pull back on the power. Those flames are not increasing the heating rate of the water and you’ll likely begin damaging the valve and thermometer on your kettle. In all cases, I highly recommend shielding the ancillary equipment on your kettle from the heat of the burner with a metal plate or other shield. Some burners come with an integral shield. A rule of thumb is that if you can’t comfortably rest your hand on the thermometer or handle of the valve it’s too hot.
Several companies offer natural gas conversion kits for their burners and include a new orifice and a flow control valve. Note that you can’t use your propane regulator on natural gas since the pressure for natural gas is much lower.
If your burner doesn’t have a natural gas option, converting it to natural gas is pretty simple. All you need is a drill and a set of bits with several small diameters (1⁄32- to 1⁄8-inch or so). The process is iterative. Increase the diameter of the orifice starting with the smallest drill size. Hold the orifice in a vise and drill carefully. Brass is super easy to drill. Reinstall the orifice and connect the natural gas hose to the burner. You’ll need a valve to control the gas flow. Note that the propane regulator supplied with your burner will NOT work with natural gas. Open the air damper about 3⁄4 open, not all the way.
Important: Place a full kettle on top of the burner; the kettle influences the burn of the fuel. Turn on the gas all the way and light. You should see pale blue flames that do not lift off the nozzles. Repeat this process, increasing the diameter of the orifice until you see the flames start to turn yellow. Stop enlarging the hole at this point. Open the damper the rest of the way and the flames should return to pale blue again. That’s it!
Final Thoughts on Gas Burners
I do hear on occasion brewers concerned with scorching or wort darkening from high power burners. But I have never experienced this to be the case. In fact, I’ve run side-by-side tests with single-wall bottom kettles and multi-layer clad bottoms and haven’t found any noticeable difference in wort darkening or heating rates between them. That said, always turn off the burner when adding malt extract as the thick syrup will quickly settle to the bottom and will scorch. Once you get it fully dissolved you won’t have any troubles.
Safety considerations are paramount for burners. Never operate indoors without proper ventilation and a carbon monoxide detector. Keep at least 15 feet (4.5 m) away from buildings, and always operate on non-flammable, firm surfaces such as concrete (remember, a wood deck is flammable). Keep children away, and wear long pants and covered shoes for burn protection. Never store propane tanks indoors — propane is heavier than air and can fill your house with explosive vapors if there is a leak.
Electric Heating Sources
Electric heating is really growing in popularity and for a lot of good reasons. The pros are numerous, beginning with efficiency and ease. Electricity provides fast, efficient heating without requiring refilling propane tanks. Electric units are ideal for indoor use since nearly all of the power goes into the water and very little is discharged into the room. They operate silently, and ventilation requirements are minimal, as you only need to ventilate the vapors created by the boil. They are also extremely economical to operate costing about $1 per batch in energy costs. The only cons with them, for the most part, are the availability of enough electrical power to operate them for larger batches, the higher equipment costs (particularly for larger batch sizes), and lastly, the lack of portability. So almost the opposite pros and cons of propane burners!
There are three predominant types of electric heating for electric brewing. Induction, immersion, and surface type heating.
Induction Heaters
Induction heating has been on the market for about 50 years and can be found in residential stovetops and small portable units as well. They work by converting the 50/60Hz AC input electrical power to high frequency AC – 20,000-40,000 Hz output power. This high frequency power is fed to a coil of wire just under the glass top of the heater (see Figure 2). This coil is an inductor (hence the name) and induces small, localized current flow in the metal placed above it. These are called eddy currents. These rapidly moving currents heat the material of the pan, but eddy currents only occur if it is magnetic material. That’s also a con for induction heaters. Most homebrewing kettles are 304 stainless steel and that material is only slightly magnetic. Aluminum isn’t at all. There are, however, a number of manufacturers that use clad bottom kettles that contain a magnetic steel plate bonded to the bottom of the kettle with aluminum. They were developed specifically for induction use. So if you’re interested in induction, be sure your kettle is compatible. If your kettle isn’t induction capable, induction interface discs are available to place between your kettle and the stove, but some efficiency is lost.
Residential-grade induction heaters are readily available for smaller kettles at 120V (these are ideal for about 2.5 gallons/9.5 L of water, although they will work for up to 5 gallons/19 L if you aren’t in a rush getting it to a boil). Larger models are available, but these commercial-sized units are a few hundred bucks and require 240V and 10-15A of current. However, they will easily handle 5-gallon (19-L) batches. They do have power control, but the models with temperature control, in my experience, are not accurate enough for brewing needs. The other drawback is that they require fans inside the device to cool the electronics that create the high frequency current. So they can be a little noisy. For much more on induction brewing, see Josh Weikert’s story “Induction Brewing” in the January-February 2018 issue of BYO.
Immersion Heaters
Immersion heaters are the most common amongst electric brewers. Immersion heaters often are repurposed electric water heating elements. The risk with using an off-the-shelf water heating element is that while the element itself is often available in stainless steel, the fitting is often plated steel. The zinc plating will eventually corrode away leaving rust and bare iron. This may lead to a metallic taste in your beer. So make sure you’re getting a fully stainless steel element. Several companies have developed elements specifically for the homebrewer using all stainless steel low-watt density designs. But most require a large hole for the weldless types, or a large sanitary fitting or NPT fitting to be welded into your kettle to install them.
A perceived con of electric brewing is wort scorching. That is where watt density comes to play. Watt density is simply the wattage of the element divided by the heated surface area of the element. The units are typically watts/square inch or watts/square cm. You’ll hear “low watt density” (LWD) and “ultra-low watt density” (ULWD) thrown around on the web, but this generally is a marketing term used for water heater elements. I’ve never found a standard that defines the exact range. Industrial heater manufacturers do make recommended maximum watt densities for water, oils, syrups, acids and others, but no recommendation is made for beer wort. My experience over the years is that anything under 60W/square inch (9.3 W/square cm) will work and not scorch your wort, and most ULWD elements are in this range. Ideally, you’ll want to be under 40W/square inch (6.2W/square cm). Unfortunately, most element manufacturers don’t publish this data. Like my recommendations for propane burners, do a web search or talk to your local retailer for recommendations. In general, elements listed as ULWD are usually fine. The most important thing is to always clean them thoroughly after each use. Built up proteins and water salts act as an insulator and this will reduce the life of the element and also lead to scorching.
Calculating watt density is a fairly simple matter. Although you’ll need to make a couple assumptions. Here is the equation to use:
Watt Density = Element Wattage / surface area of heating element
Surface area is: 3.14 x diameter x length. Length is where some assumptions need to be made. Heating elements generally have a “cold pin section” an inch or two (2.5 to 5 cm) from the fitting before the resistive heating element starts. This keeps the electrical connection and fitting from getting too hot. Using a flexible tape measure, measure the total length of the heater tube. Then subtract 3 inches (7.5 cm) from that length to accommodate for the approximate cold length. This will get you fairly close to the actual active heating length.
Lastly, you cannot use an immersion heater directly inside of your mash tun to heat your mash, even if you’re stirring. The thick mash inhibits convection and free flow of the wort so scorching is inevitable. If you are a brew-in-a-bag brewer, simply lift the bag and then turn on the heating elements. Otherwise you’ll likely scorch and melt your bag. Recirculating immersion mash systems (RIMS) work great since there is a continual flow of wort over the elements as you’re heating, but you’ll want to ensure wort is flowing any time you energize the element.
Surface Heaters
Another type of electric heating element used in homebrewing is the surface heater. This product is used in the all-in-one brewing systems that leverage commercial coffee urn designs. The construction is simply a resistive heating coil that is permanently bonded to the underside of the kettle using a ceramic material. The heat is then transferred through the bottom of the kettle. The only drawback with these heating elements is that the heat is quite intense and has a fairly high watt density, so you can get some scorching, particularly if you don’t get the kettle bottoms shiny clean after each use. Like immersion heaters, the heating rates and boil intensity are limited by the available power in your home. Most of these products are rated at 1500W at 120V in the USA. They are quite economical, though, and do include temperature control.
Electric Heat Considerations
Before you run out and install an element in your kettle, you need to do a little research on what power you need for your system, and more importantly, what power you have available in your home, and whether that power is available where you intend to set up your brewery.
In the US, residences have 120V power readily available, but 240V service is available only in select areas of your home or apartment. 120V 15A power is pretty common in homes in the US, but it really can only provide about 1500W of power max to avoid nuisance breaker tripping. Note that Power in Watts is Voltage x Amperage. That’ll be fine for a 2.5- to 3-gallon (9.5- to 11-L) batch, but it produces a marginal boil for a 5-gallon (19-L) batch. You might be able to install a 20A receptacle depending on the breaker size in your panel. But you’ll want to make sure nothing else is running on these circuits while you’re brewing. Even with a 20A breaker, you’ll be limited to about 1750W to keep that breaker from nuisance tripping. Still, this is adequate for a 5-gallon (19-L) batch. If you can get access to 240V through a dryer, oven, or have direct access to the main breaker panel, you’ll be in great shape! In all cases, you’ll want to consult with a licensed electrician to be sure the equipment will operate reliably and safely. Speaking of safety: Always use a GFCI breaker (ground fault circuit interrupter) on your heating system to prevent electrocution in the event of a failure or defect. It is always best to have a licensed electrician do the wiring.
The next step is calculating what power you need to power your brewery. First, review your brew system and process. How many kettles or RIMS heaters will you be energizing at the same time? How fast do you want to heat? Bear in mind that rarely do you heat brewing liquor from ground water temperature all the way to a boil in one step. Normally, you’ll heat from ground water temperature to strike (a temperature rise of about 100 °F/56 °C) and from there another 60 °F (33 °C) or so temperature rise to get to a boil. You will also want adequate power to generate a sufficiently vigorous boil. A 10–15% per hour boil off rate is fairly typical for homebrewing. Calculating the heating rate is pretty simple. But bear in mind, the power of your heaters is a balance of what power you have available, and what heating element wattages are available to you in the market. That said, if you aren’t into the geeky math, Chart 1, above, is a guide based on my experience as to what you’ll need for a good heating rate, and for a nice rolling boil.
Now let’s dig into the numbers:
Heating Rate (temp. rise/min.) = (Rest temp. – start temp.) / desired time.
So if I am raising my liquor from 60 °F (16 °C) ground water up to 160 °F (71 °C) strike, that is a 100 °F (55 °C) temperature rise. If I want to complete that in 45 minutes, that is 100 °F/45 min = 2.2 °F/min. (55 °C/45 min = 1.2 °C/min.). In general, a 2–2.5 °F (1.1–1.4 °C) ramp rate per minute is pretty common.
To calculate what wattage heating element is needed to achieve that heating rate is simple as well:
Watts = desired ramp rate in °F/min. x gallons of water / 0.0068
or
°C per minute x liters of water / 0.00286
It would be ideal to get exactly the heating element wattage you need, but they are only available in certain wattages. And you may not have the power available to drive it, so pick an element that is close and then use this equation to estimate your final heat rate:
Heat rate Ramp Rate in °F/min. = 0.0068 x Watts / gallons of water
or
°C per min = 0.00286 x Watts / liters of water
If you’re in the 1.7 °F/minute (0.9 °C/min.) range then you’ll get your strike water from ground water temperature to 160 °F (71 °C) in about an hour, and will generate a reasonable boil. Although 2–2.5 °F/minute (1.1–1.4 °C/minute) is ideal.
Note that while using a higher wattage heater will shorten your brew day you’ll want to be mindful of your watt density so that you don’t scorch or darken your wort. And it will also increase your boil-off rate. Of course that can be accommodated by adding more water for a higher boil-off rate, but if you have the ability to control the power output of your heating element, you can dial in the exact boil rate every time. Some controllers, and PIDs have that ability and it is a great feature to have!
Hooking it Up
So you’ve managed to get a nice element installed in your kettle and adequate power to fire it up. Can you just plug that into your wall outlet and start brewing? Nope. A receptacle and a plug are NOT a replacement for a switch! In short order (pun intended) you’ll zap your receptacle and have an impressive waft of ozone in your brewery. The inrush of full power current will arc and burn the plug and receptacle contacts permanently damaging them.
That’s where controls come into play. While a properly-sized element tuned to the perfect boil can be operated with an on/off switch, the reality is you’ll want to be able to vary the power, control the temperature, or both. There are a number of manufacturers that make controls for electric brewing and they range from about $150 for a basic control to $2,000+ for an automated system. It all depends on what you’re trying to accomplish and how much power you’re trying to control. In general, you’ll want temperature control for your strike water, and possibly your hot liquor tank as well. All that is needed for your boil is power control, or perhaps just an on/off switch. What I personally love about electric brewing is the ease in which you can control power and temperature, although that does come at a cost. But bear in mind that you’ll make a lot of that cost up over time vs. buying propane. At least that’s how I justified the investment to
my wife!
At the end of the day, both propane and electric heat sources have their place. Both will perform well and allow you to make great beer. What you as a brewer need to consider when choosing your heat source is what your individual brewing needs are. Specifically: Brewing indoors, ventilation, portability, budget, batch size, and electric power availability in your home. The decision is pretty straightforward after answering those questions.
