OzVMX Forum
Clubroom => General Discussion => Topic started by: Hoony on October 23, 2018, 06:01:18 pm
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Any of you blokes have experience with converting a bbq from lpg to to natural gas.
I bought a generic kit for the regulator hose and bayonet fitting
But jet sizes are different thread. I know you drill them out but how do you know the size. Lpg jet sizes are 0.91mm and 0.96mm
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stuff this up and you will get bang for your bucks... ;D... i hate gas.. any gas... always break out in a sweat when using gas heaters, bbq 's etc Brrr
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Double the orifice area for natural through the LPG reg I think is the start point.
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ok so if i have an orifice at 0.96mm diameter double is obviously not 1.92mm how do you double a cross sectional area of a circle.
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I did similar a couple of years ago for the son-in-law's BBQ (LPG to natural gas). The BBQ shops will not sell you the jet sizes unless you're a licenced gas fitter but if you do some homework to come up with the conversion tables to calculate the BTU's generated between the two gas sources you can work out the jet size required.
In our case I drilled the existing jets out to 1.85mm with a standard jobber drill and it worked great, from memory the jet size for the LPG could have been similar to yours. If it's a multiple burner BBQ, modify one jet and try it. If it burns a clean blue flame then you know you've got the gas:air ratio correct.
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I did similar a couple of years ago for the son-in-law's BBQ (LPG to natural gas). The BBQ shops will not sell you the jet sizes unless you're a licenced gas fitter but if you do some homework to come up with the conversion tables to calculate the BTU's generated between the two gas sources you can work out the jet size required.
In our case I drilled the existing jets out to 1.85mm with a standard jobber drill and it worked great, from memory the jet size for the LPG could have been similar to yours. If it's a multiple burner BBQ, modify one jet and try it. If it burns a clean blue flame then you know you've got the gas:air ratio correct.
1.35 mm, #54 or #55 number drill.
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What's the difference between LPG and natural gas? Where/how do you buy each?
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Alan, just go down to BBQ Galore and tell them you want to convert your BBQ from LPG to Natural Gas. They will sell you the right jets for under $5 each. You don’t have to be a licences gas fitter.
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John Natural gas is low pressure
Bottle gas is high pressure
That’s why you need to re jet
Need bigger jets for natural gas I got mine from bbq joint as ted said
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both fuel have different air/gas ratios. i have a chart that i am using to Calculate
what i need. the Key is the Burner BTU value, once you know this sizing is easy.
stay tuned.
momus is on the money as he has correctly calculated what i need.
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BTU is an interesting point. We have one barbecue that runs on LPG and another one that is the same brand and type (Weber) but slightly smaller that runs on natural gas. I think the LPG one is heaps hotter and it is better to use.
It is convenience issue but I would only go for LPG now.
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I noticed the same when I converted mine to natural gas it wasn’t as hot as bottle gas .
I only done the mod years make for the dreaded case of running out of gas half way through a bbq , but now I just use LPG with the safety valve and it has a meter on it to show gas bottle amount .
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BTU is an interesting point. We have one barbecue that runs on LPG and another one that is the same brand and type (Weber) but slightly smaller that runs on natural gas. I think the LPG one is heaps hotter and it is better to use.
It is convenience issue but I would only go for LPG now.
if the Natural gas one has not been sized correctly it wont provide the heating value as LPG. Natural gas runs at 10:1 air/gas ratio and LPG at 25:1
LPG has a much higher (nearly 3 x) energy value (MJ/m3) over natural gas.
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Alan, just go down to BBQ Galore and tell them you want to convert your BBQ from LPG to Natural Gas. They will sell you the right jets for under $5 each. You don’t have to be a licences gas fitter.
Spot on Ted, but you need to know what jets to buy...they won't or can't tell you even if you provide the burner specs.
my BBQ looks like a non standard jet size (Aldi jobby) so i will drill mine, lots of good info on youtube the charts to size and the math behind it need to be right.
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Let us know when you are going to fire it up Hoony,,, I will climb up and sit on my roof n watch ;D ;D
(https://i.imgur.com/3xAy9vw.jpg)
Well what do you know, I have you to thank Hoony for learning how to post pics again,,,
now to remember it ::)
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Read the Rules first AGA 601 ….. might pay to get a gas fitter to do your conversion as it will require a Gas system compliance plate after it has been converted.
The regulator needs to swapped and balanced also
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Let us know when you are going to fire it up Hoony,,, I will climb up and sit on my roof n watch ;D ;D
(https://i.imgur.com/3xAy9vw.jpg)
Well what do you know, I have you to thank Hoony for learning how to post pics again,,,
now to remember it ::)
Kaboomski...Ha nice.....i like it.
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Gas threads got changed a few years back and besides the previous different LPG threads there is a new one that is in fact a very old one and i think its whitworth.
As with anything they probably did this to stop the unlicenced from blowing themselves up. Its still possible to find adaptors that will go from the new to what you have but its a royal PITA. Give a gas fitter a bell and save your headache or buy a dedicated Natural gas unit.
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well done Pokey, i was wondering why my jets in the kit did not match the threads in my BBQ differnet pitch and indeed looked imperial.
i have done my research and conversed with a gas combustion engineer and can now make an informed decision for orifice sizing.
as Momus said i need a #54 drill to ream out my original jets. i guessing he (Momus) has this knowledge as well
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Hoony
if you have access to a set of number drills try going up in stages and solder/redrill the 1st jet if you go too big
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The thing with bbq’s galore is they aren’t licensed converters so they don’t know what they are really doing they just chuck the reg on and a universal injector which drill 54 is close for a cast bar burner.
As Hoony said lpg has a higher heating value so when you convert you size on mj/hr so lpg and Nat using the same mj doesn’t necessarily equal the same heat you can go incrementally bigger bit go to big and it’ll burn floaty and even though there is more gas there won’t be enough air able to flow through the burner so it won’t get hotter after a point.
Also a lot of gas taps do or don’t have turn down adjustments this is the low setting so if you convert an lpg bbq to natural and when you turn it back to low it is to low and goes out this is the turn down sometimes there is a screw on the gas tap to adjust this some times it’s pull apart the taps and size the turn down hole that can be a pain.
But you won’t blow your self up with natural gas it’s heaps safer than lpg but there’s is differences like heat value products emitted from burnt natural gas is a lot more than burnt Lpg lpg is heavier than air natural gas floats away.
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The thing with bbq’s galore is they aren’t licensed converters so they don’t know what they are really doing they just chuck the reg on and a universal injector which drill 54 is close for a cast bar burner.
As Hoony said lpg has a higher heating value so when you convert you size on mj/hr so lpg and Nat using the same mj doesn’t necessarily equal the same heat you can go incrementally bigger bit go to big and it’ll burn floaty and even though there is more gas there won’t be enough air able to flow through the burner so it won’t get hotter after a point.
Also a lot of gas taps do or don’t have turn down adjustments this is the low setting so if you convert an lpg bbq to natural and when you turn it back to low it is to low and goes out this is the turn down sometimes there is a screw on the gas tap to adjust this some times it’s pull apart the taps and size the turn down hole that can be a pain.
But you won’t blow your self up with natural gas it’s heaps safer than lpg but there’s is differences like heat value products emitted from burnt natural gas is a lot more than burnt Lpg lpg is heavier than air natural gas floats away.
good info frosty its due to a test run tomorrow, thanks for the info on the low fire turn down. also good Info TT5 Matt re solder if too large.
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Seems everyone agrees that you need a bigger orifice Hoony :o
If it burns a clean blue flame then you know you've got the gas:air ratio correct.
If it blows up then you know you got it wrong ;D
From the same club as 'tighten it till it strips and back it off a turn'
Could be bigger than Boston ;D
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if it blows up Mrs Hoony will sort my sizing of Orifice Geoff.