Author Topic: Burner to pot distance for optimum heat?  (Read 2260 times)

Offline trapae

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Burner to pot distance for optimum heat?
« on: October 02, 2018, 04:12:57 AM »
 I just upgraded to a brew stand that I am very happy with. I took my old Blichman burner and had them put it in the kettle spot and bought a new burner for the hot liquor tank.   (Mash tun Doesn’t get a burner. Single infusion insulated Ssbrewtech).  Brewed for the first time on it yesterday and everything went well but took longer to heat the hot liquor tank water as well as bring my kettle to a boil.  It has a gas manifold with a larger tubing going to it so it’s got enough natural gas, but when I try to get the right blue flame, it just took a long time. I had to turn it up to where the tips were more yellow than blue for more heat which I know is not optimal. Looking at the burners, they are on the lowest spot of three possible positions that they can be on. Just wondering if I should put them on the higher level closer to the pot and keep the flame more blue. Any opinions?
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Offline Bob357

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Re: Burner to pot distance for optimum heat?
« Reply #1 on: October 02, 2018, 07:48:54 PM »
Not sure the distance makes as much difference as where the heat is directed. If the frame of the burner blocks heat from exiting around the parameter of the kettle you lose a lot of heat energy. (If the path directs heat under the frame rather than over it.)


I had a similar problem with a new kettle that was a larger diameter than the one it replaced. I used 1/2"
 rebar to raise the kettle above the frame and allow the heat to exit around the kettle and the problem was solved.
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Offline rburrelli

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Re: Burner to pot distance for optimum heat?
« Reply #2 on: October 03, 2018, 07:38:47 PM »
Interesting. I thought that by concentrating the flame in the center of the pot it was heating more efficiently. I always tried not to let it get out over the side.
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Offline mabrungard

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Re: Burner to pot distance for optimum heat?
« Reply #3 on: October 03, 2018, 08:00:43 PM »
Interesting. I thought that by concentrating the flame in the center of the pot it was heating more efficiently. I always tried not to let it get out over the side.

I agree that centering the external heat source on the kettle bottom makes the most sense. However, its not really the efficiency that you need to worry about.

It turns out that pro brewers and manufacturers learned many decades ago that its the wort circulation in the kettle that makes the most difference in avoiding DMS and reducing heat stress on the wort. By moving the heat source to one side of the kettle, that heats wort more strongly in that area and that uneven heating can help promote a stronger rolling action in the kettle. Its the rolling circulation that brings each drop of wort to that surface interface with the atmosphere that is important. That's when DMS can actually volatilize from the wort into the atmosphere.

Sure there is going to be more heat leaking around the short side of your kettle, but you can live with that. And the thing is that you only need to move the kettle a few inches off center to get that improved rolling action. Try it out. It works.   
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Offline rburrelli

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Re: Burner to pot distance for optimum heat?
« Reply #4 on: October 03, 2018, 08:13:34 PM »
Makes total sense.  Thanks Martin.
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Offline coolman26

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Re: Burner to pot distance for optimum heat?
« Reply #5 on: October 05, 2018, 10:45:52 AM »
I use 20 tip NG jet burners.  Distance I think it is burner style specific. I love my burners, but tip to kettle had to be 15”. I wouldn’t trade them. My Shroud was as important as the distance. Forced the O2 to move into the mix. Once I figured out the O2 they clicked.


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Offline charlie

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Re: Burner to pot distance for optimum heat?
« Reply #6 on: October 06, 2018, 01:40:16 AM »
My brew rig is a 10 gallon keggle gravity HERMS rig. I replaced my BKs 6" propane banjo burner with a 23 jet NG wok burner trimmed down to 12 jets, and I'm still piddling with burner height.  In the old setup the burner was too close to the pot (about 4 inches), and the burner shroud didn't allow sufficient air flow, so I cut the shroud off and lowered it 1.5 inches with L brackets. We'll see how it works this coming Sunday.

My original concern with the setup was that, although it worked, I was getting way too much carbonization on the bottom of the kettle (lamp black, and therefore carbon monoxide too). By lowering it down I have allowed more air flow above the burner. In the test run it brought 1 gallon of water in the BK from RT to boil in 5 minutes.

I operated the propane burner with a regulator, and I had settings marked on its dial for heat, standby, and roll. I don't have any sort of repeatable control on the NG burner except for the noise it makes. I think of its settings as Whisper, Hiss and Roar. I use Roar to heat the wort to a boil, Whisper as it comes to a boil (to prevent boil over during the out-gassing phase that I call the "Foam Wait", which is usually 5 minutes), and Hiss to maintain a boil during the boil phase.

I tested the burner before I moddded the burner stand, and found that flame height in the Roar setting was about 7 inches. I feel that the ideal distance from burner tip to pot bottom is somewhere in the 6-7 inch range.

If this modification doesn't work out I'm going to find a sheet metal shop with a rolling mill and get them to make me a 12 inch diameter by 8 inch high cylinder of 16 ga mild steel and go from there.

Charlie
« Last Edit: October 06, 2018, 01:42:18 AM by charlie »
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Offline KellerBrauer

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Re: Burner to pot distance for optimum heat?
« Reply #7 on: October 06, 2018, 01:03:35 PM »
I just upgraded to a brew stand that I am very happy with. I took my old Blichman burner and had them put it in the kettle spot and bought a new burner for the hot liquor tank.   (Mash tun Doesn’t get a burner. Single infusion insulated Ssbrewtech).  Brewed for the first time on it yesterday and everything went well but took longer to heat the hot liquor tank water as well as bring my kettle to a boil.  It has a gas manifold with a larger tubing going to it so it’s got enough natural gas, but when I try to get the right blue flame, it just took a long time. I had to turn it up to where the tips were more yellow than blue for more heat which I know is not optimal. Looking at the burners, they are on the lowest spot of three possible positions that they can be on. Just wondering if I should put them on the higher level closer to the pot and keep the flame more blue. Any opinions?

Without actually seeing images of your setup, it’s difficult to offer sound advise.  I can tell you, however, that the elimination of the YELLOW tips on the flame is absolutely essential for two reasons.  First, the yellow tip tells us that there is an insufficient amount of oxygen and therefore, the fuel is not burning to its potential.  Second, a YELLOW tip tells us that carbon is being produced due to incomplete combustion and incomplete combustion can become deadly.  A clean flame is all about balance.

So, eliminate the yellow tips by introducing more oxygen, or reduce the fuel input, and move the tips to be within 3-5” from the kettle.
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