Saturday, November 24, 2012

Screwy's Aluminum Burner Frame

I bought a 32 quart boil pot because it allows me to do full wort boils without fear of having messy boil overs and overflows that are a pain to clean up from the stove top. Another benefit was that the pot was wide enough to straddle two gas burners on my stove at the same time that allows me to apply twice as much heat as before when using smaller diameter pots. So from both a convenience point of view, no more messy spills to clean up, and an efficiency perspective using two burners to boil the wort faster this larger pot is just perfect. But the one thing that bothered me was how long the cast iron burner grates held heat, which was causing my wort chilling to take longer.

Screwy's Aluminum Burner Frame
So after giving it some thought I ordered a length of 1 1/4" x 1 1/4" x 1/8" inch aluminum tubing and made my own custom burner grate. Aluminum is a very good conductor of heat and it doesn't hold onto the heat nearly as long as the cast iron grates did after flameout so cooling off the wort takes much less time now. Another benefit of using the burner frame is that it directs the flames upward towards the bottom of the pot instead of letting the flame blow outwards and away from the pot. The ends of the frame are open so I made two deflectors from a light gauge aluminum sheet and rolled them to match the radius of the boil pot.

Aluminum Burner Frame With Flame Deflectors
 Once I had all the pieces of the frame together I was ready to fire up the burners and heat up some strike water to see how well my new design worked. As expected the water heated up much faster than it did before when using the cast iron burner grates that came with the stove when I bought it. The new design kept the gas flames directly under the pot eliminating blow out and concentrated the heat where it would do the most good. I also noticed that the top of the stove around the frame wasn't as hot as it used to get with the cast iron grates, which used to be an issue too when trying to cool down the wort after the boil.

Concentrated Heat Source Equals Faster Boils
The strike water hit my target temperature in no time at all with both burners cranked up all the way and the 1/8 inch thick aluminum tubing showed absolutely no signs of melting or weakening so now I couldn't wait to boil some wort. During the very first full wort boil I noticed yet another unexpected benefit when using the burner frame, a much more vigorous boil and a more uniform 'bubble' pattern. When using the cast iron grates I noticed one side of my boilpot always had an area where the boiling bubbles broke the surface even though the pot straddled two gas burners. Now since the two burners were separated by a piece of aluminum tubing they both worked together to heat up the tubing which in turn transferred that heat to the center of the boil pot.

Burner Frame Applies Heat To The Center Of The Pot
Instead of having a single area of bubbling wort the boil now had three areas where the wort was bubbling up from the bottom of the pot. The heat was so even now that the top of the bubbling wort looked like it was split right down the middle by a pattern in the shape of the letter 'I'. I could tell I was going to have to recalibrate my pre-boil volumes now, using the burner frame definitely improved the efficiency of my boils and increased the boil off rates too. Another thing worth mentioning is that since the surface of the burner frame is perfectly even and the pot bottom sits flat on top of it with no high or low spots there are no rattling or buzzing noises either.

Concentrated Heat Produces More Vigorous Boils
To cool the wort faster it's also important to remove as much heat from the stove top and burners grates as quickly as possible because they work against the cooling efficiency of your wort chiller by keeping the bottom of the pot hot. To help cool down the stove top faster I remove the small diffuser pieces from the ends of the frame and direct the air from a small fan to blow cool air against the sides and under the bottom of the pot. It's incredible how much faster the aluminum tubing of the burner frame cools off compared to the how long the cast iron burner grates that came with the stove used to take. With that extra heat load taken off of the pot's bottom and sides the wort chiller can easily get the wort down to pitching temperature a whole lot faster now.

Faster Boils And Cooling Equals Shorter Brewdays
My gas stove has the standard gas burners that come with the average home stove and they're rated at 7,000 BTUs, I also have adequate air ventilation, to exhaust outdoors and supply fresh make up air, for all the gases and vapors produced during the boil. To calculate the CFM's needed for ventilation I added both burner's ratings together, which totaled 14,000 BTUs and then divided that by 30 and came up with 467 CFM's. The other part of this equation relates to the size of the area you need to provide ventilation for. A typical bathroom requires a complete change of air 8 times per hour or 8 ACH's in order to provide enough fresh air when in use.

Drinking Beer Is A Very Enjoyable Pastime
 To calculate the CFM's needed to comply with the ACH guidelines I multiplied the length times the width times the height of my brewroom, to get the total cubic volume of air in the room. Next I multiplied that number by eight, to represent the number of air changes per hour, and then divided that number by 60 to get the number of cubic feet per minute needed to eliminate any hop aromas from lingering during the boil. I like the smell of boiling wort and the aromas that the hop additions add to the brewroom, as do most all the brewers I've brewed with, but some folks don't and they would benefit the most when using the ACH sizing calculations to size an exhaust fan.  


  1. Very nice. I have grown to prefer brewing outside, but I do like your setup.

  2. I've found that brewing five gallon batches indoors gives me the flexibility to pick my brew days no matter what the weather conditions are outside. No more missed brewing opportunities because of bad weather, plus having a dedicated brewroom makes setting up and cleanup a whole lot easier too.