|Posted by Lynn Jacobson on August 02, 2002 at 14:50:24:|
|In response to Re: Converting propane grill to natural gas|
We are trying to convert a new bbq Fiesta Dynasty 450 mdl. and are running into the same problem of getting the information as to what size the orfice should be for natural gas conversion. Fiesta will not give any information. Although we are told by two of the reps that they have had family members convert theirs. How do you decide what size the orfice should be or be drilled out to. Is there a chart giving that info based on the number of btu's? If anyone can guide us to a conversion chart based on btu's please email. Thanks.
: 10-12 years ago, when I converted a grill to natural gas , This is basicly what I did. Just made a few inquiries about size and bought some new orfices off a rack at the hardware store.
: I just moved and bought a new propane grill. When I tried to convert it , I got: 1. it can't be done. 2. you have to buy a new valve from the manufacturer. 3. Only a professional gas installer can do that. 4.There are no ng orfices available. 5. You need a completely different burner design for NG.
: After much badgering, the manufacturer finaly told me that i needed a #43 (.089")drilled orfice.
: Nothing has really changed over the years in the burner or valve design. I assume the reason for the reluctance in supplying conversion parts and information is due to liability concerns.
: Natural gas as delivered to households contains very little CO2, it is primarily methane with a little ethane, butane, and propane, mixed in. Most CO2 is removed from the natural gas as soon as possible after it leaves the well head to minimize corrosion problems. Most ethane , butane , and propane (and some other nasty stuff)is removed so that it can be sold separately for more money. NG has a btu value about 40% of propane and requires about 40% as much air to burn. therefore the orfice must pass 2.5 times as much gas. NG is also generaly supplied at a lower pressure so the orfice must be more than 2.5 times bigger to supply enough ng. The BTU rating of natural gas is 1027 btu/scfm. Since the gas is 95% methane and 5% variable composition, this figure can't vary more than 5% and in practice, varies much less than 5%.
: : Problem is basically one of modifying the burner for burning of natural vs bottled gas. The bottled gas is far richer than nat gas. Being a "natural" product that is produced by gas or oil wells, nat gas has a high amount of CO2 (which basically dilutes the combustible constituents) and, therefore, more of the natural gas product must be burned than the bottled gas you are now using in order to get the same amount of heat or BTUs. The procedure for doing this is to increase the size of the orifice at the base of your burner assembly. The size of the orifice is dependent upon the pressure of the gas (a constant for home applications), the BTU rating of the gasseous fuel you are burning (your gas company will know the BTU rating of what they are putting in their distribution system) and the BTU rating of your burner. There are charts that will give you orifice size for nat gas based upon burner size (BTU rating of the burner). This info can be had from either your local BBQ shop or your local gas company. Since you will be going to a larger size orifice, you will have the option of either carefully drilling out your present orifice with the proper size drill or of buying a new orifice of the proper size. Unless you feel capable of carefully drilling the old orifice, just buy a new one of the proper size. Without a drill press, sometimes the drill can get away from you and you will get an irregular, ragged hole of uncertain size.
: : The orifice is a small brass fitting of approx 1/4 or 3/8" diameter. A new orifice can usually be bought for around a dollar or so. If you decide to just buy a new orifice, you will need to locate and remove the old one and take it with you to the BBQ store. There are several styles of orifices, depending upon BBQ burner manufacturer. You will need the old one to know the proper style for the new one.After conversion of the orifice and change-over to natural gas, you will need to adjust your air intake of your burner to get a proper combustion mixture. This will amount to loosening a screw and rotating an air intake assembly for proper colmbustion. Note the color of the flame before you change fuel or orifice size. Proper adjustment is to open the air intake so as to just get a blue flame at full gas input. My best suggestion here is to have someone who knows this procedure to do the adjustment. Often your gas company will send a service man to check proper adjustment of any of your gas appliances.
: : You will receive lots of discouragement from everyone you will talk with about a conversion. Your BBQ shop will want to sell you a new BBQ (which will be identical to a propane model with exception of orifice size and mixture adjustment!). If you are in doubt of any step, seek professional help from either a BBQ shop or your gas company. You certainly do not want to get into the situation where you have a lot of unburned nat gas that collects and burns off suddenly (called an explosion). A lot of personal and property damage could result.
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