Supercharging a natural gas BG14 burner

[bsent]

My air feed only goes into the venturi area about an inch. I understand Hockeyman's concerns, but with such low pressure air and the additional venturi space along with the burner jets, there isn't any way for this to become plugged and force the air back into the gas feed - it's just not going to happen.

I've also tried increasing the orifice size for more gas flow (as Hockeyman suggests), but that just results in a richer flame with a lot of unburned gas. You can't increase fuel flow without increasing air flow - one doesn't work without the other. The bottom line is that the design of these burners does not support sufficient air flow when using low pressure (7" WC) fuel. The higher pressure propane usage on these burners works because the velocity of the fuel pulls in air through the venturi.

My original tests (on my old brew rig) used the exact same gas lines, valves, etc. and only changed the burner from a wok/jet burner to a BG14. Fuel feed was the same, but since the wok burners had 10 tips, that means 10 gas orifice's and 10 venturi's. Each tip is able to mix/burn fuel much more efficiently due to the better air flow at the combustion point. The problem with the jet burners though is that they sound like a jet! I hated the noise, especially when 2 or 3 were running at a time. We now have normal level conversations around the brew rig because the BG14 burners run silent.

Unlike a normal supercharger on an engine, this is not a pressurized system. This is an "air assist" system to get more air up to the point of combustion.

Also FWIW, when I built mine out I tested the air pressure where the duct meets the venturi and it's ~1.7" WC (vs. 7" WC where the gas feeds in). Like Jon, my duct pushes into an open venturi. If I could find a way to create a total blockage at the burner, air/gas would simply flow back out the venturi as that is the lowest pressure path.

A check valve might be a good safety addition to any gas appliance, but I have a hard time seeing a practical situation where this setup could create any significant back pressure.

 

[JonW]

Also FWIW, when I built mine out I tested the air pressure where the duct meets the venturi and it's ~1.7" WC (vs. 7" WC where the gas feeds in). Like Jon, my duct pushes into an open venturi. If I could find a way to create a total blockage at the burner, air/gas would simply flow back out the venturi as that is the lowest pressure path.

A check valve might be a good safety addition to any gas appliance, but I have a hard time seeing a practical situation where this setup could create any significant back pressure.

I'm glad you actually tested it as I didn't, but I knew the fan pressure would be less than the gas pressure. I agree with you, and have a hard time seeing where this could create any back pressure into the NG system to create a catastrophic event as has been suggested. It's simply not a sealed and pressurized system.

 

[dahlseid]

Good luck with that! Please report back your findings as you do your tests.

I am using the BG-14 type burner that I got from Brewers Hardware with NG and am using their NG valve/orifice, which has a 1/8" ID. On their site, they report these are designed to run at 11" WC and will produce 60,000 btu; whether this is for NG, LP or both is not clear. I control my burners using a BCS-460 to activate Baso BG1100MAAK-1G furnace ignition control modules that run Honeywell VR8345M valves and direct spark ignition and separate flame sensor. I've been running it for about two years, and it works nicely. After finding this thread, I decided that I would like to get all I could out of my burners as implemented on my current stand.

A little research and some measurements and I learned that, with my valve outlet pressure setting maxed out, I was supplying NG to my burners at 5.5" WC (consistent with valve specs). My NG inlet pressure is 11.7" WC, so I was able to step up my outlet pressure to 7" through 11" WC by changing the NG spring on my value for the LP one. This worked to jack up the flame, for sure, but it also seemed that as I increased the pressure in 1" WC steps that it progressively reduced the number of burner ports that generated/sustained a flame and progressively burned more rich, as evidenced by ever increasing orange amidst the flames.

I'll post below links to short videos of the burn attempts at 7", 9" and 11" WC. In the 7" WC film, you will see that I wave the flame to get all ports to light, which they do but which the burner does not sustain. In the 11" WC, I get ignition but the burner flames out and activates the ignition control shut off.

I seek any insight or perspective any of you might have to share. I have it that, according to tables available to gas fitters, 11" WC with this burner and orifice should be putting me close to 80,000 btu potential, and that I should get 60,000 btu at 5" WC (thanks hockeyman!). I am going to clock my gas meter to see where I am at with all this when I get the time.

For now, I am wondering if I am just throwing more pressure at this burner than it can manage. Clearly, with the pressure set higher (and without a supercharger), the point where gas can ignite is higher. This may require resetting the location of my spark ignitor, and it may be a difficult optimization. It has also been suggested that changing to a pilot light would ease the process of providing ignition to the gas at the higher ignition points that accompany higher pressure.

What do you all think? If I pursue a pilot, I can use the pilot light port already on my valves and would use the intermittent pilot strategy, so I may be asking for advice on how to convert my direct spark ignition/sensing in the most cost effective and reliable way (recognize that cost effective and reliable may be in tension with each other).

Thanks for completing a long read. Fire away...

Seven inches WC

Nine inches WC

Eleven inches WC

 

[dahlseid]

I'm glad you actually tested it as I didn't, but I knew the fan pressure would be less than the gas pressure. I agree with you, and have a hard time seeing where this could create any back pressure into the NG system to create a catastrophic event as has been suggested. It's simply not a sealed and pressurized system.

JonW, bsent has indicated NG pressure of 7" WC. Have you measured what pressure NG you have going to your burners?

 

[JonW]

JonW, bsent has indicated NG pressure of 7" WC. Have you measured what pressure NG you have going to your burners?

I believe I'm right around 7.5" WC.

A quick read of your previous post tells me that you're trying to increase the fuel to your burners, but you're failing to increase the air - which is the whole point of this thread. Since the NG gas flow pressure is so low, there is not enough gas velocity to pull sufficient air in through the venturi. Do a simple test with a mattress inflator or some other air device to give some additional air to the venturi of your burner. You will see the light! (the blue one, lol).

 

[dahlseid]

I believe I'm right around 7.5" WC.

A quick read of your previous post tells me that you're trying to increase the fuel to your burners, but you're failing to increase the air - which is the whole point of this thread. Since the NG gas flow pressure is so low, there is not enough gas velocity to pull sufficient air in through the venturi. Do a simple test with a mattress inflator or some other air device to give some additional air to the venturi of your burner. You will see the light! (the blue one, lol).

Thanks JonW. I agree with your interpretation. I was looking for a few reference points to give me some direction on what to set me outlet pressure to. I want to dial that in first, and that should put me in a good spot to try the air assist. Thanks again!

 

[dahlseid]

I believe I'm right around 7.5" WC.

A quick read of your previous post tells me that you're trying to increase the fuel to your burners, but you're failing to increase the air - which is the whole point of this thread. Since the NG gas flow pressure is so low, there is not enough gas velocity to pull sufficient air in through the venturi. Do a simple test with a mattress inflator or some other air device to give some additional air to the venturi of your burner. You will see the light! (the blue one, lol).

I was able to get some information from Brewers Hardware about the burners I bought from them. They wrote, "The 11” WC is for LPG. The NG burners are the standard 7” WC most all homes have for NG. The manufacturer says this: This low pressure burner that measures 10” in diameter, venturi is tapped for 1/4” FPT for orifice valve installation, burner mounts using four lugs on perimeter which are pre-drilled and tapped and at 11” W.C. consumes 56,500 BTU/hr."

Digging further at the manufacturer's site, it says these produce 52,000 btu/hr with NG and a 1/8" orifice (and no super charger), though it doesn't specify the NG pressure...presumably it is 7" WC.

Have those of you who are running these with ~7" WC NG and a supercharger or air assist clocked your gas meters to determine btu output?

 

[JonW]

Have those of you who are running these with ~7" WC NG and a supercharger or air assist clocked your gas meters to determine btu output?

No, I have not.

 

[bsent]

No, I have not.

Me neither. All of my tests were time to heat typical strike water volume between two known temps. I don’t really care how much fuel it takes ;-)

 

[fosaisu]

I'm interested in trying out a 12v squirrel cage fan. If I'm going to buy this one:
https://www.kr4.us/blower-squirrel-cage-12v.html

any advice on powering it? I don't have a brew stand, so really just looking for a cheap wall-wort that I can strip and attach to the leads on this fan to get it running. I'm not an electrics guy, so any advice would be much appreciated!

 

[calgary222]

"just looking for a cheap wall-wort that I can strip and attach to the leads on this fan to get it running."

That's exactly what I did... I don't throw stuff out so I had a pile to choose from.

I bought these twice, a pair for my stand and a pair for my keezer:

https://www.amazon.ca/dp/B01N6Z3L7G/?tag=skimlinks_replacement-20

Cheers!

 

[JonW]

I bought these twice, a pair for my stand and a pair for my keezer:

I'd love to see pics and/or video of the air injection on your stand! I've been using the fans on my HLT and BK for over two years now and it makes such a HUGE difference.

 

[calgary222]

I'll try and get a pic tonight - "but it ain't pretty" - all I did was take a 3" piece of copper pipe and flatten one end enough to jam into the bg14 venturie, electrical tape the other end to the fan and then ran the wires from I think a 9v wall wort... I noticed a big improvement in the quality of the flame, but never did a scientific time to temperature test.

Edit:

Pics here, pic two shows the simple electrical tower, each socket has a switch in the panel, both fans run together - not pretty, works well. Note that I lifted my kettles by the 1" to improve airflow.

 

[Ansoncadams]

Yes, I use the same blower you linked. I've since added a second one for my HLT tank. They work pretty good. I tried using a variable speed controller, but the fan didn't respond well with it. I use a strip of duct tape about 3/16" wide that is across the duct tube to lessen the air flow just a little.

I have a stainless tube that is ducted up to my burner so that I can keep the blower motor under my stand with the rest of the wiring stuff. It makes for a really clean installation.

I have thought about drilling out the NG orifice to see if I could get even more gas flow. It would likely no longer work without the blower attached as it would be way too rich, but that's not an issue as I always use the blower.

bsent - please update here with any other tests/findings you come up with.

I personally am very happy with the performance I'm getting now using the air assist. It is nearly equivalent to the wok/jet style burners I previously used, but is silent instead of the incessant load jet engine noise. Also, putting the blowers under the rig also help minimize any sound from them.

Jon, Amazing Rig! I'm also a fan of the full stainless. I built mine weld-less out of a SS Kitchen Table.

Where did you purchase the SS Duct from?

I'd like to do the same for my rig. I have the same squirrel cage blowers and BG14s. Except I've drilled the orifice to get more gas out.

Thanks

 

[JonW]

Jon, Amazing Rig! I'm also a fan of the full stainless. I built mine weld-less out of a SS Kitchen Table.

Where did you purchase the SS Duct from?

I'd like to do the same for my rig. I have the same squirrel cage blowers and BG14s. Except I've drilled the orifice to get more gas out.

Thanks

The SS tube that I run the air into was custom made by Brewers Hardware. Give them a spec and they'll make it!

I like to hide wiring, valves, etc. under the diamond plate shelf, so I wanted to do it that way for looks. The pics above from Calgary222 looks to be a pretty simple setup too. One additional benefit of having the fans under my shelf is that it helps to cut the fan noise (not loud by any stretch, but helps to keep it pretty quiet).