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Increasing heat for a gas grill

zwiller

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That stinks. I'll let you guys geek out on the BTU per inch2 but seriously, high grill heat is a must. Steaks are like 4m for us. Crazy good sears and flavor is fantastic. Time saver sure but the results are at least 2-3 levels above your typical grill. No way I will ever go without a sear burner. Good luck!
 

bregent

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I appreciate your help but it doesn't answer my inquiry. It's an engineering question.
Sorry, forgot to address that. The gas flow is limited by the orifice and regulator, not the burners. Drilling out the burners will change the flame pattern, but not increase the BTU by any noticeable amount.

Unfortunately, even with the sear burner on my Weber NG, I can't get a very good sear for steak. I use charcoal or a cast iron pan when I need that much heat.
 
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schlotz

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One cubic foot of propane = 2,516 BTUs compared to one cubic foot of natural gas = 1,030 BTUs. Propane contains more than twice the energy of natural gas. Ergo why the orifices for propane have smaller openings, but even with that, you will find grills set for LP usually run hotter then the same that are set for NG.
 

pmarc

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One cubic foot of propane = 2,516 BTUs compared to one cubic foot of natural gas = 1,030 BTUs. Propane contains more than twice the energy of natural gas. Ergo why the orifices for propane have smaller openings, but even with that, you will find grills set for LP usually run hotter then the same that are set for NG.
That's a stunning fact. I see the Genesis® II S-310 uses NG at 39,000 BTU per hr.
Not the best metric? But a heck of a lot better than the 21,000 Btu per hr of the Fuego. And I bet the Fuego's 21,000 isn't for NG. This is the problem. But I ain't gonna undo the 50' ng pipe I ran to my deck! Can you imagine its likely I'm running 60% less than 21,000 ! A match would be better. At least I won't have to lie about why I'm selling it. Use propane is my motto. And most people will.
 
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schlotz

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My bet is they aren't going to provide much more than what they (Weber) already have: i.e. BTU-per-hour
 
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zwiller

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I thought I was pretty well versed in this stuff due to homebrewing but no idea propane was 2x hotter than NG.
 

pmarc

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A friend just told me he fixed 2 grills. By drilling out the choke points, not the burners. One grill a double burner, the other with 10 burners. But he started with propane lines on both. Mine is the ng conversion kit. So I wonder if it's now max'd out for the burners or if I can drill out all brass orifices even more. Prob have to drill out the bruner holes, too. Using proportions for hole size as a guide.
 
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bill1

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... BTW is it actually possible to find watt-per-area (heat flux) numbers for grills? Is this metric better than BTU?
Take the published BTU per hour value. Divide by the area of the lowest (largest) grate/grill. You want that number to be big. (If you want high temps and quick warm-up.)

You can use BTU/h or watts. You can use square inches or acres. Just be consistent in your use of units.

Yes, heat flux is important. If you kept the lid open (open flame) it's all that counts. With the lid closed, the raw power (BTU/h) matters too.

It's like buying a car by horsepower because you want to accelerate fast. What's more important is power-per-weight ratio. But that hasn't really caught on, has it?
 

pmarc

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Take the published BTU per hour value. Divide by the area of the lowest (largest) grate/grill. You want that number to be big. (If you want high temps and quick warm-up.)

You can use BTU/h or watts. You can use square inches or acres. Just be consistent in your use of units.

Yes, heat flux is important. If you kept the lid open (open flame) it's all that counts. With the lid closed, the raw power (BTU/h) matters too.

It's like buying a car by horsepower because you want to accelerate fast. What's more important is power-per-weight ratio. But that hasn't really caught on, has it?
That would be... [ 20,000 BTU/hr / 225 sq inches ] = 89 Currently. How does this guide me to how big to drill the burner holes?
 

bill1

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...But I ain't gonna undo the 50' ng pipe I ran to my deck...
If you're not moving your grill around, natural gas is a great convenience. Ask my wife if she'd like to be changing out propane bottles on her kitchen stove.
And please don't drill out anything unless you TOTALLY understand what you're doing, including elementary thermodynamics and fluid mechanics. An orifice is a key safety feature...it is not a choke point to be casually enlarged.
 

JJS

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That would be... [ 20,000 BTU/hr / 225 sq inches ] = 89 Currently. How does this guide me to how big to drill the burner holes?
Since it appears we can’t talk you out of this project I have attached the orifice size chart, you need to remove the orifice in each burner control and look for the number stamped on it, this will give you your starting point, once you have that info you then need to search for an orifice drill set and pin vise.
The problems come in when you don’t get the orifice size perfectly matched to the burner holes and fire either comes rolling out the back of the burner or you have super long yellow flames that burn like crap and produce CO and soot.

I would keep this grill as far as possible from anything flammable.
* if you do cause property damage and the insurance company investigation proves you DIYd your grill they will likely tell you to pound sand on your claim

good luck


 
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pmarc

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Since it appears we can’t talk you out of this project I have attached the orifice size chart, you need to remove the orifice in each burner control and look for the number stamped on it, this will give you your starting point, once you have that info you then need to search for an orifice drill set and pin vise.
The problems come in when you don’t get the orifice size perfectly matched to the burner holes and fire either comes rolling out the back of the burner or you have super long yellow flames that burn like crap and produce CO and soot.

I would keep this grill as far as possible from anything flammable.
* if you do cause property damage and the insurance company investigation proves you DIYd your grill they will likely tell you to pound sand on your claim

good luck


Thanx. And no, I'm not adamant about doing this. Not at all. Just collecting information, which I thank everyone for. So, I'm digesting the chart. The orifice number is found in the chart. And that will indicate its BTU/hr capacity. Which presumably will closely match the manufacturer's claim for the type of gas used (in this case ng since the ng kit was used). If this is correct, I'm missing the next step...which is what? Am I to pick the new BTU/hr desired and bore out the orifice to the diameter indicated? How do i know the burners will accommodate whatever i pick?
 

bill1

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OK, pmarc, JJS gave you the keys to the kingdom so I might as well give you the shove. It sounds like your Fuego was never converted to NG, so you're going to do it.
You have to have a box of small numbered drills for both drilling and to use as gage pins. Note these small drills are brittle/fragile and vary by only thousands of an inch. If you're not used to such watchmaker tolerances like this don't try it. If you break a drill off in the orifice you have a brick for a bbq.
What size orifice do you have now? Since it's propane, the universal regulator size for propane bottles is 11"wc (water column of pressure) the orifice size will give you the BTU/h in the last column. If a #55 drill fits but a #54 doesn't, you have a 20000 BTU/h unit.
Next you HAVE to get a regulator for natural gas--you can't plumb direct to a grill. For 1/2" piping, a good size for a regulator is 3 or 4 inch-wc.
Many are sold for both LP & NG applications. That's impossible. That means you have to disassemble it and (usually just) reverse a part so the regulator spring is less compressed for the lower pressure NG application.
Let's say you have purchased, and verified the spring setting, for 4"wc. From the table (for our example case of starting with 20000BTU/h propane) you will need to enlarge the orifice to a #44 hole to get 20000btu/h for 4"wc Nat Gas. Of course you would start several sizes smaller and work your way up.
Don't take shortcuts and make sure you understand what you're doing. Good luck.
 

pmarc

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OK, pmarc, JJS gave you the keys to the kingdom so I might as well give you the shove. It sounds like your Fuego was never converted to NG, so you're going to do it.
You have to have a box of small numbered drills for both drilling and to use as gage pins. Note these small drills are brittle/fragile and vary by only thousands of an inch. If you're not used to such watchmaker tolerances like this don't try it. If you break a drill off in the orifice you have a brick for a bbq.
What size orifice do you have now? Since it's propane, the universal regulator size for propane bottles is 11"wc (water column of pressure) the orifice size will give you the BTU/h in the last column. If a #55 drill fits but a #54 doesn't, you have a 20000 BTU/h unit.
Next you HAVE to get a regulator for natural gas--you can't plumb direct to a grill. For 1/2" piping, a good size for a regulator is 3 or 4 inch-wc.
Many are sold for both LP & NG applications. That's impossible. That means you have to disassemble it and (usually just) reverse a part so the regulator spring is less compressed for the lower pressure NG application.
Let's say you have purchased, and verified the spring setting, for 4"wc. From the table (for our example case of starting with 20000BTU/h propane) you will need to enlarge the orifice to a #44 hole to get 20000btu/h for 4"wc Nat Gas. Of course you would start several sizes smaller and work your way.
Don't take shortcuts and make sure you understand what you're doing. Good luck.
My best next move is to get a good installer to do it right. It was ng converted, but the fact you say a regulator is required - I see none - suggests this system was done wrong.
 

JJS

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Thanx. And no, I'm not adamant about doing this. Not at all. Just collecting information, which I thank everyone for. So, I'm digesting the chart. The orifice number is found in the chart. And that will indicate its BTU/hr capacity. Which presumably will closely match the manufacturer's claim for the type of gas used (in this case ng since the ng kit was used). If this is correct, I'm missing the next step...which is what? Am I to pick the new BTU/hr desired and bore out the orifice to the diameter indicated? How do i know the burners will accommodate whatever i pick?
you need to know your manifold pressure (after regulator before burner controls) which will require you to insert a way to hook up a pressure gauge that reads inches of water column. At that point you can refer to the chart and see what each burner is rated for.
You will then need to use the number drills to determine what size the holes in the burners are and divide the # of burner holes by total BTUs of the burner. once you figure out how many BTUs you would like to be at you adjust the main orifice to what the chart says then do some math to see how many more holes the burner needs and hope you were close when you fire it up
 

pmarc

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Wanting to check if indeed the installer used ng orifices... I removed one (of two) which ties directly into the burner. The number on it doesn't make any sense for
purposes of the BTU chart... It's either 1.06 or read upside down 90.1 . The second orifice, to the other (much larger ) burner is about double the hole diameter and reads 1.7. So I'm sure the first one isn't 90.1. It's 1.06.


Orifice.jpg Orifice.jpg
Orifice.jpg
 
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