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Bluesin

C5Longhorn

is it possible to convert a grill from natural gas to propane?

23 posts in this topic

Correct me if wrong:

 

75'000 BTU 6 burner BBQ = 12'500 per burner.

 

12322 BTU (NG) = #58 Orifice (http://www.hvacredu.net/gas-codes/module2/Gas%20Orifice%20Capacity%20Chart.pdf)

 

#58 Orifice = 1.0668mm.

 

Assuming the orifices are drilled to 1.0mm, Would this work? Consequence would be slightly less BTU - is there any else?

 

#60 or 1.0mm orifice would deliver 11176 BTU (NG).

 

It's ALOT easier (local hardware) to get a 1.0mm drill bit, compared to a #58 drill bit (eastern europe).

 

 

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First you don't say what brand/type of grill you have, next if in fact you have 6 burners it IS 75000 BTU FOR THE ENTIRE APPLIANCE NOT PER BURNER. So now you have to figure out if you're going to use a 7" EC or the required by most LP appliances 11" WC. Also many grills have different valves between their NG and LP appliances (Weber being one of them). Also the ID tag on the grill is giving you a total BTU for the appliance. If you have a side burner, rotisserie burner, etc. those burners are included in that total reading. Just saying tread carefully

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Hoods last four words in his post should be heeded.

 

Not only do some grills use different gas valves, some manufactures use an inline regulator (AOG) that you must take apart and flip for lack of correct word a "reed" for the appropriate gas being used in addition to changing orifices.

 

Additionally on some grills (AOG/Holland) they mix orifice. Holland main burner and searmate are diff. AOG main burners/side burner/rotis burner all diff sizes.

 

Bottom line know the BTU rating of each (main burners, side burner and rotis burner) for your grill.

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First you don't say what brand/type of grill you have, next if in fact you have 6 burners it IS 75000 BTU FOR THE ENTIRE APPLIANCE NOT PER BURNER. So now you have to figure out if you're going to use a 7" EC or the required by most LP appliances 11" WC. Also many grills have different valves between their NG and LP appliances (Weber being one of them). Also the ID tag on the grill is giving you a total BTU for the appliance. If you have a side burner, rotisserie burner, etc. those burners are included in that total reading. Just saying tread carefully

 

Thanks for your comments. I intend on treading very carefully, hence why I haven't jumped to any conclusions without triangulating my information with others. I will NOT be like this guy who just guessed at the orifice size and choice of material to reduce the hole: (

)

 

underthehood, it is a Weber Summit 675 (built in NG). From what I can tell it is identical to the Summit 650 (likely the same series as your summit 450), except for the manifold.

 

The regulator does have a reversible LP/NG configuration.

But failing this I will revert to an 11"WC propane regulator.

 

I will fully leak check the setup and proceed with valves on the lowest setting initially before lighting. I understand the Weber NG valves let more gas through and will be difficult to fine-tune.

 

Re: BTU rating consists of all burners and side burners. From what I can tell, this BBQ did not come with a side burner. But, would Weber rate it at 75'000 BTU to include an optional side burner?

 

Please confirm this rule of thumb: "Flame should be 1 - 1.5" high with no or very little yellow."

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Just an observation that doesn't make sense:

 

The current NG orrifice is approximately 1.2mm (caliper visual measurement).

 

This would be between #56 & #55 on the BTU charts. Which would be 3/64" or 0.0469".

 

The BBQ is rated for 4.5" WC NG. This orifice would be 6333 BTU per burner for NG according to the charts.

 

6333 x 6 burners = 38'000 BTU.

 

This is VERY different from the 75'000 BTU rating.

 

Any idea why?

 

Or is there typically 50% extra BTU to accommodate side burners?

 

EDIT:

 

A visual caliper reading is VERY inaccurate. I just measured with a toothpick (put permanent market on the orifice and stuck a tapered bamboo toothpick into the orifice until snug then measured where the mark on the toothpick was). It shows as 1.45-1.50mm depending on toothpick rotation.

 

1.4mm = 0.0551", #54 orifice is 0.0550" and 8709 BTU.

 

8709 x 6 = 52'000 BTU, leaving 22'000 BTU unaccounted for.

 

Looking better?

Edited by Koula

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The tag will only carry the BTU rating of the grill as Weber built it. There seem to be different vintages of the 6XXX grills from Weber. Does your model have a rotisserie burner? If so that most likely is accounting for 15K BTU of the rating. The typical Weber grill runs about 10 -12K BTU per burner in my experience BTW.

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No rotisserie, smoker, or side burner. Just 6 identical burners.

 

I'm inclined to go with a 1.0 mm hole, as it's easy to get this drill bit. This would be approx 11000 BTU at 11"WC LP per burner. 66'000.

 

Would this be too hot and too difficult to modulate with the NG valves?

 

Alternatively, I order a smaller drill bit and match the existing NG BTU rating (post above) at 52'000 BTU. LP orifice size 0.9mm or between #65 and #64.

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I am a little stumped. Every conversion I have done has been LP to NG not the other way. But IMO I would go with a #60 and work my way up from there based on grilling performance. I always fine tune. I have a set of drills and I work on the very low end and work up from there. My reasoning is that I don't have the ability to do it with the precision the factory has. I.E. I know my chuck will have slight "runout" and such so my theory is you can always go bigger but you can't go the other way

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