Direct Fire Brewing – Pros and Cons

We’re discussing direct fire brewing today, looking at the pros and cons of this heating method. It’s the third our series of articles about brewhouse heating.

Following on from the first article brewing with electric and the second which was brewing with steam.

Direct fire brewing, as the name implies involves using an open flame under your brewhouse kettle to heat it up. Back in the day this would of most likely been a coal fire. However modern-day breweries who use direct fire, generally employing oil or gas for the burner.

What Do These Burners Look Like?

The burner is usually housed in a cast iron combustion chamber placed under the kettle, which distributes the heat across the bottom of the kettle.

These burners can sometimes have several flames allowing for a more even distribution of the heat across the bottom of the kettle. There are other options which push the heat through a “coil” in the kettle too. We’ll look at this option as well.

Villages 3 Vessel Brewhouse Side View - Direct Fire Brewing
3-Vessel Direct Fire Brewhouse by Bespoke Brewing Solutions (BBS) for Bay 13 – It’s A Little Different In the Design

Direct fire can be used for a mash tun, however it’s rarer because the mash easily sticks or scorches due to localized hot spots. As we noted in our electric brewing article, most direct fire systems are quite inefficient.

They heat up the air around the kettle as well, meaning up to 60%+ of the “heating” can be lost. That’s why direct fire kettles are usually below 330HL (281 US Bbl.) in size.

Although, most modern breweries will go to 10bbl (11.7HL) for direct fire, or 15bbl (17.6HL) for indirect fire as a maximum length for a brewhouse. Anything above usually means steam.

Different Types of Direct Fire Brewing (There’s Also Indirect Fire Too)

Direct Fire Under the Kettle

So, imagine a heating source directly under your brew kettle. In can be a firebox or an open flame gas burner directly under the kettle. The heat source can be either gas or oil.

Direct Fire Under the Kettle

So, imagine a heating source directly under your brew kettle. In can be a firebox or an open flame gas burner directly under the kettle. The heat source can be either gas or oil.

==>Make sure your burner and flange match up in the design phase plus your burner is far enough in otherwise it can be a fire hazard<==

As in the pictures above, you see the gas burner is outside the kettle. The heat generated goes in into the “firebox” underneath the kettle and heats up the wort.

Most brewhouse suppliers would recommend a direct fire kettle to about 10bbl (11.7HL), with anything above being steam heating. Although larger direct fire brewhouses exist as we mentioned earlier.

Indirect Fire

An indirect fire system is the same principle, utilizing a burner (a bit like a jet engine), however it “blows” heat into a jacket.

Which works very similar to a steam jacket in brewing, which most people are aware of. The advantage is more even heat distribution and greater heating efficiency over direct fire.

Internal Coil Indirect Fire

The last and maybe the most interesting is having an internal helical coil in your brew kettle. Similar to indirect fire, however, instead of the heat going to a jacket, it goes into the coil inside the kettle.

This leads to more efficient heating as the coil is internal and has more time and surface area to heat exchange with the wort. So, the heat transfer is better than both direct and indirect fire. I first came across this option when speaking with Bespoke Brewing Solutions (BBS for short).

Direct Fire Brewing - Lanemark Design for Internal Helical Coil Collage
Some schematics designed by Lanemark for the Villages Project by BBS

I’ll let Bespoke Brewing Solutions explain…

“We worked with Lanemark Combustion to install their TX tank heater ( system in the kettle of Villages Brewery (tag them) for a 10BBL (11.7HL) brewhouse in London, UK.

Villages initiated the project and we at BBS were able to work with Lanemark on manufacturing the coil and other components. We also incorporated the control of the burner into their brewhouse control panel.”

John and Harry from Bespoke Brewing Solutions (BBS)

Please note: You can follow @Villages Brewery on Instagram.

The Lanemark system is actually pretty slick, the system is modulating and pre-designed to control temperature and pressure. So, less work for the brewer and super efficient.

For more information on the TX system from Lanemark please read the dedicated article by clicking this link.

Direct Fire Brewing – Safety Issues

When working with an open flame, there are obvious dangers which you need to be aware of. Different brewhouses have alternative safety features. However, a common option is:

  • When you turn the kettle on, a solenoid opens to allow the electronic ignition of the pilot to light
  • If this fails then everything automatically shuts down
  • If the pilot light sensor determines the pilot is lit then another solenoid opens to allow full flow of gas to the main sensor.
  • There is an air blower which feeds to air to help it burn

Direct Fire Mash Tun?

Now I’ve not seen much about using direct fire mash tuns so, what I write is what I’ve researched online and got from trawling forums. There are apparently a few direct fire mash tun setups around.

However, for obvious reasons they’re not too popular. You use a (forced air) burner under the mash tun to heat it. Some advantages are:

  • It’d be quick for heating a mash
  • No need to pump the mash elsewhere (unlike with electric)
  • In theory you could do decoction boiling or gelatinization rest directly in the mash tun, with the liquid mash pumped to the lauter

Now for the downside….

Direct fire could lead to denaturation of enzymes due to hot spots or extreme temperatures. You could scorch your grains leading to off-flavours. Furthermore, it would be a pain to clean plus, the general wear and tear on the metal of the vessel is a real consideration.

Indirect Fire Mash Tun

You’d get the same advantages as listed above for a direct fire mash tun but, with more even heat distribution. So, in theory it could be more efficient to heat.

The negatives are, a burner gas is hotter than steam (in the jackets) so scorching and denaturing could still be an issue. Also, you’d need to make sure the whole of the jacket is covered as well so, the decoction process might not be possible.

The Advantages of Direct Fire

When it comes to direct fire, there are a few advantages to using it which are:

Initial Costs and Space

The initial cost of installing direct fire is cheaper to install and calibrate than a boiler. Furthermore, it takes up less room if you’ve limited space available. It’s cheaper to run than electric in most parts of the world.

Villages 3 Vessel Brewhouse - Direct Fire Brewing
3-Vessel Direct Fire System

Ease of Use

It’s not only cheaper but easier to set up. There are no boilers, no boiler rooms, no steam piping, no steam traps and so on. There are also less operational headaches.

Switching Out

If you’ve the option to use propane and natural gas with your burner, it could lead to less downtime, as it might be possible to switch to the other if there’s an issue.

Disadvantages of Direct Fire

Local Requirements

Like steam, you will need to check your local regulations. If your location has strict building codes, then, a forced air direct fire system can trigger certain requirements. At the end of the day, you’re working with an open flame so, a fire suppressant system may be required.

Heat Dissipation

Due to the inefficiency of direct-fire designs, the exhaust coming from the flue can get quite hot and potentially dangerous, if not insulated or vented correctly. You will notice in the pictures supplied by BBS they insulate the flue up to the top of the kettle for safety reasons.


You have a greater chance of caramelization with direct fire. However, with proper design and jet calibration this problem may be less of an issue.

In some beers the mild caramelization could actually be a benefit. However, for lighter beer or lager, it could be an issue. Also, another issue is the level of caramelization isn’t easy to control either.

Furthermore, residual heat in the firebox will continue to heat the wort even after you turn off the burner. This is why it is important that your burner supplier comes to test your system and dial in the burner.


As mentioned in the mash tun section, direct fire can be hard to clean…

With direct fire, having the heat source at the bottom, means the excessive heat can lead to some deposits which are hard to remove. Also, the “char” on thanks from direct fire can look unsightly and need cleaning.

Direct Fire Brewing - Bay 13 With Flue
Sometimes the bottom can get “charred” from the fire

Direct Fire Brewing Conclusions

For many people on a budget, direct fire may represent the best option as the initial start-up costs are cheaper/easier than steam. It’s also cheaper to run than electric. Furthermore, direct fire brewing takes up less space than steam, plus maintenance is easier too.

Depending on your building codes, for a smaller operation direct fire might be the best option. You do need to be aware however caramelization can be an issue, especially if you’re making lighter beers or lager.


The downsides are localized hotspots leading caramelization and being hard to clean. Also, there’s wear and tear on your tank over time. Furthermore, if your set-up isn’t properly designed you can end up warping your vessel!

When using direct fire, depending on your set up, make sure you go for the “turbo” system. Using an air blower to help with the burn. A similar system that’s natural aspirated (no forced air) can take much longer to heat up your kettle and be less efficient.

Of the three choices; taking into consideration your budget, circumstances and needs, the best option might be the coil inside the kettle using indirect fire. I would suggest talking to your preferred manufacturer when discussing the right set up for you.


I’d like to thanks Bespoke Brewing Solutions (BBS) and Lanemark for there help with this project. Adrian from Lanemark for giving us permission to use his drawings and schematics.

Lanemark are based in the UK and please feel free to reach out to them if you need a direct fire system for your brewing project.

Bespoke Brewing Solutions are a equipment manufacturer based in China and have done brewing installations all around the world with projects in the UK, Australia, The US and further afield.

Bespoke Brewing Solutions John and Harry

All photos in this post are provided by BBS.

They’ve done several projects for AB InBev in South Korea, India and China and worked with Carlton United Breweries too. Feel free to reach out to Harry and John and speak with if you’ve got an upcoming project.

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For the other articles in the brewery heating series please see the links below:

Brewing with Electric (Part 1) – For the pros and cons of brewing with electric click here.

Brewing with Steam (Part 2) – Find out why many brewers prefer steam in their brewery click here.

Brewery Heating Options Wrap-Up (Part 4) – To discover which is the best heating option for you and why click here.

Lanemark TX Burners (additional content) – For a dedicated piece on the benefits of a Lanemark TX Burners system please click here.

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Who Am I?

Hello, my name is Neil, I’ a British brewer based in China. I first came to China in 2010. I’ve been lucky enough to have brew on a number of systems, in various parts of the world in my 25-year brewing career.

I now assist people with their brewing projects, helping people in a number of ways from recipe formulation to sourcing brewing equipment.

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If you’ve an upcoming brewery project and would like some help, or simply want to talk with someone, then please feel free to email me

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I’m currently advising on projects from the UK to New Zealand. I’m happy to answer some initial questions you might have and assist in any way I can.

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Thanks for taking the time to read my article today, I hope you found it useful. Have a great day and happy brewing.



Neil Playfoot

Neil is a brewer with 25 years international brewing experience. Based out of China (first came in 2010) he works as a brewing consultant helping brewers with their projects and brewing processes. To find out what services Neil can provide your brewery please click here. If you'd like to contact Neil you can email at
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