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JoeLee
04-13-2010, 04:39 PM
Wondering if anyone out there has any knowledge of gas burners?? Air fuel ratios, preassures etc.
I made this fireplace about 8 years ago because I got tired of buying cheap die cast grills with cheap .020 400 series stainless burners that lasted about 2 years before they flaked and crumbled.
I did all the brick work and made the stainless racks and front door. It has two slide out racks, one for the lava rocks and one for the food. I spaced the racks the same distance apart that the grill manufacturers use as well as the distance from the burners, the food rack is actually about 2" closer to the burners than the store bought grills. I made the two burners out of 1" dia. stainless pipe with a 1/8" wall. They won't burn out any time soon. The fuel supply is propane. I had to change the regulator on the tank because the standard barbecue grill regulator wouldn't allow enough gas through to run both burners.
The gas valves and knobs came off an old gas stove. I machined a manifold for them to mount into and ran black iron pipe from the valves to each burner
orface in the back wall of the fireplace. The problem is it takes about twice as long to cook anything in this fireplace than it does on a store bought grill.
A big dissapointment after all this work. If I crank up the gas to get more heat the flames turn orange and start to burn off the burners and will flameout. If I lower the gas to get a nice even blue flame about 1" high I don't get enough heat. I'm not sure if the problem is related to air / gas mixture, oriface size or if that is all I can get out of these burners. Orange flames is a sign of not enough O2. The holes in the burners are .105 in dia. I spent a alot of time walking off all those holes in the mill. Two rows per tube.
I'm wondering if I drill out the holes to maybe 1/8" would make a difference. Before I buthcher any of my handy stainless work I'de like some input.
Any help would be much appreciated.

JL........................


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JoeLee
04-13-2010, 04:43 PM
Here is a picture of the air intake of the burner.

The center hole is where the oriface goes in. I just push the burner to the back of the fireplace, they line right up. The open area around the center hole is the air intake. I never made the covers because I figured they were not getting enough air to begin with.
This was all hit and mis. More mis.

JL..............

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jeremy13
04-13-2010, 05:42 PM
Ok first question. Are the burners getting there fresh air from out side of the fire box? Where the burners connect to the orifice is there fresh air coming in there? Will the burners burn correctly out side of the fire box at the presser you want to use? If you increase gas presser you need to decrease gas orifice size. This will increase the venturie effect and suck in more air. And increasing the burner ports will decrees the internal presser in the burner allowing more air to come in. There is a fine balance that is hard to find.
Looking at what you have I would go to .125 on the burner ports. And a #53 wire size drill at the orifice and 10psi. Should give you about 80,000btu.

jeremy13
04-13-2010, 05:47 PM
Just another thought what size pipe did you run from the valves to the burners. And if you used the valves from the old grill they wont stand up to 10psi. They'll leak around the stem.

JoeLee
04-13-2010, 06:17 PM
Jeremy, looks like you have most of the answers.
I'm not sure what the preassure is. I did try a couple different oriface sizes. I'm not sure what size is in there now. I'll check. What ever size it is it works better than the previous size I tried. The burners get thier air from inside the fireplace, no way to really get outside air in there, thats why the front door has the vents at the bottom. I never tried burning them outrside the fireplace to see how they work. That would be a good way to tell if they are starving for air.
Your are correct in saying that it's a fine line to getting them to burn perfectly.


JL..............

JoeLee
04-13-2010, 06:25 PM
Forgot to mention the valves.......... Yes if I crank up the preassure too much the valve stem will pop out of it's seat and gas will leak by the O-ring seal at the valve. It's happened a couple times, I just push it back in.
I suppose that would be an easy fix.

JL............