Converting Member's Mark BBQ Grill from Propane to Natural Gas (LP to NG)



Last Updated April 2nd, 2012. I'm quite happy with my Member's Mark BBQ Grill but as a "big-dog" BBQ, it uses quite a bit of propane. So I converted it to Natual Gas ... and in the process, took some pictures & notes so I could write this how-to guide. Note that while it is specific to the Member's Mark Y0101XC BBQ Grill, the same general concepts/thoughts apply to other Barbeque grills and actually any appliance (or anything) that uses LP or NG.

BTW, I want to thank Daniel K. Schuster (aka Dannos) who posted his notes on doing a LP->NG conversion and was a wealth of information and support while I did mine. If you have any comments/suggestions/additions/etc. to this, send me an Email ... and also your favorite BBQ grill recipe! ;-)

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Disclaimer: I am NOT a gas/grill/whatever expert. Anything you do based on what is written here you do at your own risk. Converting the Member's Mark BBQ Grill to Natural Gas VOIDS the warrenty. Do NOT call me if you melt your grill, burn down your house, etc.

A - Why would one convert from Propane (LP) to Natural Gas (NG) (2003_08_02)

A-1: What are the advantages to converting from Propane (LP) to Natural Gas (NG)?
A-1: (2002_07_08) There are two main reasons - convienence and cost.
a. Convienence: With LP, you have to make sure you have enough gas in your tank(s) and refill as needed. And unless you have a second tank, you will probably run out halfway through your big family BBQ - dooooppppp! ;-) BTW, running the 3 mains on HIGH, you will go through a 20 pound tank of LP in about 8 hours. With NG (assuming you have a utility gas line to your house), it is always there; you just turn the handle and you are grilling!
b. Cost: A 20 pound tank of LP is about 425,000 BTU's and costs about $13 to refill (more if you tank exchange). My Natural Gas is billed in Therms (100,000 BTU) and once you factor in all of the taxes, is about 50 cents/Therm - i.e. just over $2 per "equivelent BTU's" tank of Propane - that's a savings of over $10/tank! ;-)

A-2: What are the disadvantages to converting from Propane (LP) to Natural Gas (NG)?
A-2: (2002_07_10) There are actually several disadvantages to converting.
a. With LP, you can move your BBQ around, whereas with NG, the location becomes somewhat fixed ... although a long flex gas pipe can give you some mobility.
b. With LP, you can cook even if the gas company has some sort of problem delivering gas to your house (disaster recovery! ;-)
c. Converting requires some time/expense (although not much).
d. You can not go "back/forth" between LP & NG without some work, and once you have done LP->NG, it is harder to go back.
e. Once you have converted, you will probably BBQ more! ;-)

A-3: What tools do I need to do the LP->NG conversion?
A-3: (2003_08_02) Standard tools: screwdrivers, needle nose pliers, wrenches, etc. You can get by with a standard set of drill bits, but a "numbered" set of bits is extremely useful, but you only need to drill a few holes, so hopefully you can borrow these. You will need some pipe joint compound for all threaded connectors - essential if you don't want to blow yourself up! A digital camera is quite useful so you can take pictures of things as you take 'em apart - that way you can put 'em back togather again correctly - especially useful for the orifices and valves. It is helpful, but not neccessary to know the regulated gas pressure - either call your gas company or build your own manometer for a couple of bucks - this is actually useful for flow analysis too.

A-4: How long will it take to do the LP-NG conversion?
A-4: (2002_07_08) Probably about an hour or so to do the 3 mains, side, and back burners. However, as noted below, you will want to do your initial drill holes on the small side, and drill 'em bigger as needed ... so there will be some additional "futz factor" time in there as you test the grill; so maybe a good excuse to tell your spouse you need to make some steaks! ;-)

A-5: How much will it cost to do the LP-NG conversion?
A-5: (2002_08_05) Basically nothing - all you are doing is basically drilling a handful of holes a little bit bigger. Note that if you have a "conversion kit", you pretty much have to do all of this stuff anyway, so why not save yourself a few bucks! ;-)


B - Issues with getting Natural Gas to the BBQ Grill (2006_09_05)

B-1: What type of pipe/connectors do I need?
B-1: (2003_09_03) Assuming you allready have NG for your house, you will need to find a place to "T" off of that and run a line outside your house close to your grill. Standard "iron pipe" or the "flex gas" pipe can be used - just be sure to follow code. Pay close attention to the run-length/pipe-diameter/BTU-usage ... there are specs that tell you what diameter you will need given the run length and BTU requirement. Factory "max" on the Member's Mark is all three mains on high plus the side burner (back burner should not be operated with mains are running), so this would be 66,000 BTU - to be on the safe side, I'd just say 80,000. Pipe is cheap and it's a pain to re-run it ... err on the big side ... and be careful using "skinny" pipe the last few feet to the grill. What I did is shown in the "gas-line" web page.

B-2: What about using quick-disconnects/rubber flex line to the BBQ Grill?
B-2: (2006_09_05) I don't quite see the point in using a quick-disconnect. It's not like you are going to want to move your 200 pound grill somewhere! And if you look at these, it's typically a pretty skinny diameter pipe where the disconnect is, so this can prevent adaquate gas flow. While you CAN run rubber flex line to the BBQ grill, be careful with the inside diameter. Because you have to deliver a higher volume of gas with NG, I had problems using 1/4" inside-diameter hoses ... and ended up using a 3-foot 1/2" flex-metal connector (typically used for dryers, hot water heaters, etc.). Using a manometer or measuring flow rates at the gas meter will help you determine if you have a "lack of adaquate flow" to the BBQ grill itself, especially when all three burners are on HIGH, plus the side burner. UPDATE: CraigB points out that "Here in Florida we have to have QD's in order to make life much easier prior to a hurricane. I have two-grills and a Weber fireplace that have to be disconnected prior to the 120 MPH winds, and moved to our overhang which is then shuttered in" - hurricanes aren't an issue in Colorado, but great point Craig - thanks! ;-)

B-3: Do I need a regulator?
B-3: (2003_09_03) You should not. Before the pressure enters your house, it should go through a regulator and flow meter installed by the gas company. See what this looks line on the gas-line web page.

B-4: What is the NG pressure?
B-4: (2003_02_12) Most people report around 7" water pressure, but you should check with your gas company to make sure. Or better yet, build your own manometer for a few bucks and actually measure it - quite easy to do.

B-5: How do I make sure there are no leaks?
B-5: (2002_07_08) As mentioned numerous other places, you should be applying a soapy water solution to ANY work that you do not only along the way, but at the end. I put about 1/3 Palmolive and 2/3 water in a spray bottle and I went through a couple of these during my work. Here are more details and pictures.


C - Some Misc. Physics of Gasses (2008_09_17)

C-1: What is the relationship between orifice size and BTU output?
C-1: (2002_07_14) Assuming adaquate air for clean combustion (ALL blue flames are your friend), BTU output is a function of the "burn energy" of the gas (higher for Propane versus Natural Gas), the size of the gas orifice (larger is more BTU's), and the input pressure (more pressure equal more flow rate). Grillparts has an excellent chart outlining this here that given a desired BTU output (and type of gas and pressure), what size orifice you need. And a similar, but more complete/detailed chart is available from ISC. While I think this is a good "first-start", I seemed to have other factors going on that required slightly larger diameters.

C-2: How do I measure BTU output?
C-2: (2002_09_03) One can attempt to measure BTU output by measuring temperatures, but this can be time consuming and was not all the repeatable; especially if there is any wind. It turns out you have an excellent way to measure BTU output - the cubic feet/hour of the NG as measured by your gas meter. Fire up the grill and use your stop watch to measure how many seconds it takes for a cubic foot (or whatever) or NG to flow, and then calculate the Cubic Feet/Hour. The gas company measures your usage in terms of cubic feet although typically shows it on the bill in terms of hundreds of Cubic Feet which is often abbreviated CCF. One Cubic Foot of gas is nominally 1,000 BTU, but there will be a conversion factor on the bill to convert to therms which takes into account altitude, temperature, and energy content. For me, that multiplier is about 0.8, so for instance, if I measure 75 Cubic Feet/hour (CFH), this would be 60,000 BTU's; assuming perfect combustion.

C-3: How much CFH/BTU do I need and what was your experience?
C-3: (2002_07_14) You MUST have enough NG flowing into the grill itself before you start drilling out the orifices. As noted above, it is fairly easy to measure Cubic Feet/Hour and convert that to BTU's (it's about one-to-one at sea level). I also had the manometer hooked up, so in certain cases, I could measure the gas pressure (at the side burner) and see how it was dropping under load. So after being "reasonably" sure there were no ignition sources nearby (for the first couple of tests, gas is just venting into the atmosphere), I did the following:

   WC"   CFH    Location
   N/A   200    From 1/2" iron pipe next to grill
   N/A    80    At end of 4' rubber "LP" hose with 1/4" inner diameter - discarded!
   N/A   155    At end of 3' 1/2" flex pipe and 1/2" to 3/8" connector at grill
   TBD    72    1 main burners on HIGH, orifices REMOVED
   TBD    98    2 main burners on HIGH, orifices REMOVED
   TBD   105    3 main burners on HIGH, orifices REMOVED

   6.5   N/A    No gas flowing
   5.9   TBD    1 main burners on HIGH, WITH orifices 
   5.2   TBD    2 main burners on HIGH, WITH orifices 
   4.5    80    3 main burners on HIGH, WITH orifices 
   4.1   TBD    3 main burners on HIGH, WITH orifices plus back burner on HIGH
Conclusions: I initially used a 4' rubber "LP" hose that has an inside diameter of 1/4" ... this did NOT provide adaquate flow to the grill. The 3' 1/2" flex pipe (with 1/2" to 3/8" connector at grill) does some flow restriction. Even so, it appears that the grill connector itself (I recall this was 5/16" inner diameter) and the manifold further limits the CFH. Note that the manifold has an "LP" sticker on it - I kinda wonder if there is a larger diameter version that says "NG" on it. The drop in gas pressure concerns me a bit and suggests that I would be better off with a shorter run from the regulator and/or even larger diameter pipe so that it could reduce the pressure drop when under load.

C-4: Are there altitude issues?
C-4: (2008_09_17) I live in Boulder, Colorado (actually Lafayette) and having an aeronautical engineering degree, I said to myself that altitude should NOT play a factor here - relative pressure (i.e. 7" WC) is the same amount of gas at sea level as it is a mile high, and as long as I had enough air to get good combustion (no yellow flames), it should not matter. However, it turns out that for various appliances they DO sell high altitude orifices, which are SMALLER than those for sea level. My theory on that is that it is easier to de-rate the appliance with an orifice change than it is to ensure one has enough volume of air (at the thinner higher altitude) to support complete combustion. Or optionally you could put a turbo and/or supercharger on your burners to insure enough air for a proper stoichiometric mixture. So I'm not sure what is going on there ... but the bottom line is I DO believe there is some sort of altitude affects going on, and you will need more CFH at a mile high to generate the same BTU's as at sea level.

C-5: Is LP or NG dangerous?
C-5: (2002_07_08) Don't be a winner of a Darwin Award! Not only can LP and/or NG cook your steaks, it can melt your grill and/or blow up your house (or worse). Be careful, be sure to check for leaks, and hire a professional if in any doubt.


D - Actually converting the Grill (2012_04_02)

D-1: What diameters did you end up drilling out to?
D-1: (2012_04_02) For the main burners, I ended up with #40-0.098" (stock is #55-0.052") for the orifice (HIGH) and #54-0.055" (stock is ~#61-0.039") for the control valve (LOW). YES, #40 is pretty darn big; but I was trying to insure that with all three main burners on HIGH, I was able to deliver adaquate gas to heat the grill up quickly. Lets just say I can sear my steaks pretty darn good! ;-) For the side burner, I ended up with #47-0.078" (stock is #59-0.041") for the orifice (HIGH) and did NOT need to change the control valve for LOW.
For the back burner, I ended up with #50-0.070" (stock is #61-0.039") for the orifice (HIGH) and #54-0.055" (stock is not selectable) for the control valve (LOW). As noted below, it's pretty easy to change the back burner from OFF/ON to OFF/HIGH/LOW. While I would like an even lower setting, I was worried about flameouts due to wind, so I erred on the conservative side. BTW, there's a bit of grease on these parts, and my wife wasn't too happy when they spilled onto the kitchen tile so keep things neat.

MartinB sent the following related Email in April/2012 - good info to share - thanks!
"Your website was very helpful in my conversion project. I started with the Members Mark Conversion Kit and drilled out the orifices using your notes. I found that for the Main Burner I realized good results with a #44 orifice and #58 for the control valve Low orifice. The Side Burner turned out a lot of heat with a #51. The Back Burner ran very well using a #54. The conversion kit utilizes a NG Regulator which may explain that all sizes are running 4 sizes smaller than your notes indicate. Again, starting our small as you suggested allowed me zero in on the correct size. Feel free to include this information on your website for anyone else ready to enjoy the freedom of cooking with Natural Gas."

D-2: How do I drill out the orifices?
D-2: (2002_07_11) The orifice diameter controls how much gas flow occurs in the HIGH setting (ON in the case of the back burner) and therefore sets the maximum BTU output. If this is too small, your grill won't heat up fast enough and/or be hot enough in general. Make this too big and you will "overrate" your grill - you might not have enough air for clean combustion (yellow flames are bad) and/or other stuff like maybe even melting your grill I guess! ;-) Click here to see exactly how do drill out the orifices.

D-3: How do I drill out the control valves?
D-3: (2002_07_11) The control valves regulate the flow of gas by turning it OFF and ON and provide variable output. How does it do that? Remember that the orifice diameter is fixed, so at the OFF setting, no gas flows. At the HIGH setting, the control valve lets "lots" through, since the orifice will regulate. And at the LOW setting, the control valve has a smaller opening than the orifice, so it becomes the limiting factor. Any position in between gets some volume of gas in between. Click here to see exactly how do drill out the control valves.

D-4: How do I make the back burner variable in heat?
D-4: (2002_08_17) Look carefully at the control valve section above. For the back burner, the "ring" section only allows rotation of 90 degrees for OFF/ON ... rather than 180 for OFF/HIGH/LOW as with all other control valves. It does this because the "groove" which the D-ring sits is only 90 degrees. So ... you have a couple of choices on how you can handle this:
      - Drill out the groove (somehow) for 180 degrees of motion
      - Remove the D-ring, so then it won't hit the stop
      - SWAP "ring" sections with one of the mains.
I did the later, since I want to have fine control over the back burner and "know" where the stops are ... whereas for the main burners, I'm not as concerned - plus I can see the control knob positions easier relative to the other ones ... plus if I go to far and it flames out, I typically have other burners on, and it will re-ignite (I swapped with the center one). Note that after this, you will need to drill out the back burner control valve as outlined above - see D-1 for what I used - you'll need to do experimentation on your own ... and I recommend doing this at night so you can see the flames. Since the back burner is typically lit by itself, you want to drill it conservatively large, since you do NOT want this to flame out, since there is no nearby burner going to re-ignite it. Although I have not done too much "spit BBQ'ing", I really like having this tuneability ... as I can crank it down if I feel I'm charring the outside of the chicken too much.


E - Testing/Tuning the LP->NG Conversion (2002_08_17)

E-1: How to do I determine if I drilled things out enough?
E-1: (2002_07_14) As mentioned above, there are several things you can look at. I emphasize that I'm not a "grill expert" (or Certified Grill Expert - CGE for those that get the inside joke! ;-) so these are the "futz" factors I used and you can can tune/tweek your grill how you want it. Note that all of the above applies even if you leave your grill on Propane, but want to fiddle with it a bit. The "BTU/orifice size" charts would probably be the "official" approach, but these weren't that useful to me. Looking at the CFH and converting that to BTU's was darn useful ... and also watching the temperature (and just grilling) was how I arrived at what I did.

E-2: What should the flames look like?
E-2: (2002_08_17) Click here to see some pictures of Alek playing around ... ;-)

E-3: What should the flames REALLY look like?
E-3: (2002_08_17) A common question is what should the flames look like. I have a some pictures of before-LP/after-NG (and after-LP - FIRE! ;-) that will show you what this looks like. Click here to see various flames shots.


F - Safety Notes (2008_04_03)

F-1: How do I make sure there are no leaks?
F-1: (2002_07_08) As mentioned numerous other places, you should be applying a soapy water solution to ANY work that you do not only along the way, but at the end. I put about 1/3 Palmolive and 2/3 water in a spray bottle and I went through a couple of these during my work. Here are more details and pictures.

F-2: How do I use the manometer to check for leaks?
F-2: (2006_01_07) First, you need a manometer which will cost you about a buck to make. Plug this into the side burner orifice as shown, and with the gas supply OFF, open the side burner control to HIGH. Then open one of the MAINS to HIGH; and then close it when manometer is in a stable position - it should be level, if it's not, you goofed something up. While leaving the side burner control on HIGH, turn the gas supply ON. The manometer should respond and eventually stabilize at the regulated gas pressure. Mark this location, and then turn the gas supply OFF. The manometer reading should NOT move; this is basically testing everything downstream from the gas supply valve up to control valves of the BBQ. Note that it does not test any leaks past that; such as the tubing to the back burner or the orifice's themselves - you will need to use the soapy stray approach on those. Standard disclaimer applies, but nothing is completely airtight - I feel that if you take at least 5 minutes to bleed off an inch of pressure, you are probably OK.

F-3: What do I do if I have a leak?
F-3: (2002_07_08) Usually, this will simply require tighting the connection. In some cases, you should put pipe dope and/or pipe tape in place seal things - definately for "pipe" fittings, questionable for flare fittings. Always be careful tightening to make sure you don't bend any pipes in the process.

F-4: What do I do if I smell gas?
F-4: (2008_04_03) Sending me an Email is NOT the right thing to do ... as actually happened when someone emails me asking "There seems to be a gas smell coming from our outdoor gas grill (which is already hooked up to natural gas). How do we UNHOOK the gas to the grill? Thanks for responding." I responded to this person saying "Uhhhhh ... if you are smelling gas, you might consider calling 911 rather than sending out an Email" ... but my Email bounced ... so unknown if Darwin'ism got applied here.


G - Personal Experiences & Misc. Other Notes (2008_03_18)

G-0: How does one use liquid oxygen to REALLY sear your steaks?
G-0: (2002_08_05) Yea ... you can get quite a "sear" using liquid oxygen to BBQ (archival link)

G-1: Does this REALLY work?
G-1: (2002_08_05) I've been grilling for months with Natural Gas and love it.
Daniel K. Schuster (aka Dannos) posted his notes on doing a LP->NG conversion and says he hasn't cook meat in his oven since!
Here is an Email from Roy Brotherhood with some detailed notes on his conversion.

G-2: What about converting other grills?
G-3: (2002_08_05) The process should be quite similar on other grills. For instance, you can buy a gas conversion kit for the Virco grill, but owners have told me that if they were to do it over again, they would probably just drill it out - you end up doing pretty much all of the above anyway. I recently assisted a friend convert his Kenmore grill and it was uneventful using these notes.

G-3: I converted my grill to NG - what do I to with the LP tank gauge?
G-3: (2002_08_07) See if anyone with an older MM grill (this feature was introduced in 2002) wants to buy it - anyone want to buy mine?!? ;-) Or hotwire the connectors with a paper clip so that it always reads FULL ;-)

G-4: Can I convert my grill from NG to LP?
G-4: (2008_03_18) You can ... but this is the opposite of everything written above ... and making holes SMALLER is MUCH harder than drilling 'em out to be bigger. If you do decide to do this, be very careful since if you say, drop some solder in there to close up the hole, if it melts and/or opens up, then you will have a blow torch on your hands - I personally would not recommend/try this. An approach recommended by WallD is to use a small ball peen hammer to close (or nearly close) the opening, and then drill it back out. Brass is fairly soft, but be careful not to ruin the threads. Note that if you find someone who wants to convert their grill from LP->NG, you could swap valves/orifices with 'em - here's what the label on their grill should look like. Otherwise, your best bet is probably to contact the manufacturer, but again, I would be very careful doing an NG->LP conversion.

G-5: Your How-To Guide is AWESOME ... can I Email you to say thanks and/or buy you a beer?!?
G-5: (2007_11_09) I'm delighted my web page has been helpful to 'ya - click here to Email me and/or buy me a beer - a surprising number of people actually do - thanks in advance! ;-)