Natural Gas Calculations with Banjo Burner?

I've been doing a lot of reading, learning quite a bit, and thought it was about time I ask for help to clarify and confirm.

1. The limiting factor of output of a Banjo burner on natural gas is the air Shutter, correct? We could in theory have a larger orifice for higher volume of Natural Gas and higher BTU/hr, but there is a limit as to how much air can be through the shutter to allow the proper mixture.

2. How big of a supply hose would I need to ensure that the supply hose is not the bottleneck for 2 burners? A 10 foot 3/8" ID hose would have too much pressure drop to supply the volume needed over a 10 foot run, correct, so I need to look at 1/2"?

3. My houses natural gas regulator seems to be adjustable from 7" to 11"WC. I only have a hot water heater and a furnace hooked up to NG, and they are in the same room as the regulator. Any reason not to turn it all the way up to 11"WC to increase the potential BTU output of the burners?

A lot of views but no replies, after doing more research I will try to answer my own questions for others, but don't consider me an expert!

1. I am still under this impression. I have found some additional tips though... you should fine tune your orifice size with your shutter actually closed just a little bit. This way, if you go 1 step too far, you can correct for it by opening the shutter. Also, temperature and other seasonal factors can impact the air intake, so it is good to give yourself a little bit of room to play with at max flow.

2. I think a 3/8" ID hose would work if it was a VERY short distance, but not at the ~10 feet I need, I'm assuming this is due to resistance causing pressure drop. I found a very helpful chart here that will tell you what ID pipe/tube you need for a given length and BTU requirement: http://caloreequipment.com/media/downloadDocument/id/14

3. I can't find a lot of information on people doing this, it seems it is not very common to run NG at 11"WC, not sure why.


Also, the best price I've found on 1/2" NG hose and disconnects was at the same site I linked to above, I ended up going with a 12 foot 1/2" ID hose with a quick connect that has an integral ball vale: http://caloreequipment.com/products...valve-quick-disconnect-gas-connector-kit.html

Figuring out NG on my new stand and came across your thread. Any updates?

What I would like to know is what is the maximum BTU I can get out of a 10' banjo burner using household pressure NG?

I set mine up like this:
household supply 1' pipe > 3/4" pipe > 3/4" ID gas hose > 3/4" manifold on stand > 1/2" x 4" pipe > 3/8" ID x 12" flex hose > orifice with 1/8" hole (is the Blichman burner converter orifice).

I got a nice flame out of the box with no adjusting...



...but wondering if I can get more.

I calculated BTUs being delivered by watching the needle on my gas meter while this burner and only this burner was running. With the ball valve wide open, burner used 5 cubic feet NG in 5 min 37 seconds - assuming 1,031 BTU/cf that gets me to just over 55,000 BTU/hr.

If I increase the orifice size will I get more BTU/hour out of this burner or am I already at the limit for what this burner can do?

Almost done with my NG rig and will be making a post once I've tested boil times, but I did increase to 9/64ths on my 7" WC supply.

e: I think it could be increased a bit more since I can close the shutter some and still get good flames, but I'm going to do a boil test first.

I did do a boil test with my burner (first). Took 5 gal from 106 to 181 in 20 minutes. Lid off, 65 degrees in garage with door open but not windy day.

That test indicates I got about 9300 BTU/hr into the water (well probably more because I didn't account for kettle loss).

This lead me to the gas meter test to check whether I am getting enough gas to the burner. With 55k btu/hr reaching the burner but only 9300 reaching the water I am at 17% efficiency. In comparison published efficiency for Blichmann and their test of the Bayou Classic were 31% and 26% respectively (based on boil times vs btus). Household gas ranges tend to do even better. Note the 55k btu/hr to the burner is pretty close to Blichmann's claimed 60k for the floor burner converted to NG.

So with these results I think I will focus on improving heat transfer to the kettle before I try adjusting the Orifice. Probably a wind screen around the banjo will focus heat to the bottom of the kettle better and improve efficiency.

You'll need some exhaust venting or it will choke the flame. I found that in my initial burns - it burned perfectly without the kettle on, but with the kettle and the windscreen (even with the back vented), the front jets would choke and come back, choke and come back. I'm going to add a small bit of distance between the kettle and screen to compensate for that next I think. Hopefully 1/2" or so will do it.

Even so, I got ~17 gallons to a boil in a little over an hour, so that was encouraging.

I am looking at clearance between the Blichmann Floor Burner wind screen and the kettle bottom. I can't find a decent picture with a tape measure in it but looks to be at least 1" of clearance.

I mounted my bg14 5 inches from the bottom of my keggle by mistake. I meant to put it at 4 but screwed up. It's easily adjustable though. Anyway, brewday came last week and I couldn't get a vigorous boil. Bummer.

Specs

bg 14 on NG, 25ft of 3/8 rubber hose from house piping, connected to 5 ft of 3/8 inch rubber hose from Lowes to connect from the 25 foot hose to valve, then burner.

I just ordered 25 ft of 1/2 inch rubber hose. I'll update when I know. I had a tough time connecting air hose to burner, thus the short "propane" hose from Lowe's. Seems like a short copper connection is the most popular. Thoughts?