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Convert NG to LP 1950's stove

Post in 'It's a Gas!' started by eclecticcottage, Feb 15, 2012.

  1. eclecticcottage

    eclecticcottage Minister of Fire

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    I think I may have found my new stove..maybe. It's a 1950's era Bengal, but it's set for NG like pretty much EVERY stove I find! How do we convert this to LP? I know it involves orifice size and a regulator, but that doesn't really mean a lot to me. This isn't a super popular brand like magic chef or tappan, so trying to find info on line so far hasn't gotten me much info specific to it. I did try emailing a propane company a week or so ago about switching to thier service and if they would convert an older stove and never heard back (big surprise).

    I was going to go with an early 20's/30's stove, but I REALLY like the 50's era stoves and this one would match one of the retro new fridges they make like they weer made for each other:

    [​IMG] [​IMG]

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  2. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Some of these older unit were designated for one type of fuel & non-convertible.
    Check to see if there's a rating plate on the back or inside one of the compartments.
    That plate may contain the info on the conversion requirements. Otherwise, you may
    have to take it to a licensed repair shop to see if it can be done.
  3. eclecticcottage

    eclecticcottage Minister of Fire

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    Hm. Good to know. I'll have to ask. Do you know if the older ones (20/30's) were the same? I figured this would be a project, but I didn't think it would be quite this frustrating! When we bought the Old House, I wanted a vintage stove but we didn't want to put that much weight on the spot where the stove would logically go. So, no old stove. When we bought the Cottage, it was A-#1 on my list, since I've spent 12 or so years wanting one (ok, really, a lot longer since the only reason I wanted a Holly Hobby oven when I was a kid-ONLY Holly Hobby, NOT an Easy Bake-was the fact that it was made to look like an old wood cook stove). I found a Chambers in a color I LOVE, but it's several states away. Of course THAT one is converted to LP. Everything I find locally, even out in the country, is NG it seems. I tried contacting a stove repair shop somewhat nearby and they don't "work on 1900's stoves" so I was hoping to find a way to do this ourselves. I'd love an old wood cook stove with the gas option, but I think those all have wood ovens (then again, I don't know how often I'd use the oven in the summer). Plus I'm not so sure our insurance company would love that idea! Also I don't know that I could find one in good, working condition that wouldn't cost a fortune either...and I'm not so sure how we'd move it, much less get it into the Cottage, lol.
  4. eclecticcottage

    eclecticcottage Minister of Fire

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    Just for reference, http://www.antiquegasstoves.com/pages/parts/gas.html has a valve about mid page for @ $50 that is supposed to convert from NG to LP with no orifice changes. I'll have to see if they think it will work with the Bengel. 30" vintage ranges are not easy to find.
  5. eclecticcottage

    eclecticcottage Minister of Fire

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    Just another update in case anyone is interested. The company did get back to me on the valve, but they didn't state if it would specifically work for the Bengal, just that it was as I figured, to be used to convert from NG to LP or LP to NG without any other changes, including orifice changes. We're going to look at the Bengal tomorrow and hopefully haul it home. The seller believes it has a way to be converted in the supply line, so I am thinking it has a reversable valve already (I had looked at a different stove that did, but it was too big to fit in our kitchen). That seller stated the stove came with it, and you just had to flip the regulator and adjust the orifices. I can't believe I might have my vintage stove finally. Now if we could just find some faux brick linoleum (we actually already have faux brick lino, but it's not in very good shape after all these years)....lol.
  6. 49er

    49er Member

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    Congratulations on your new stove, I sure hope it works out for you. We have one of the Heartland reproduction stoves and it has the reversible regulator to go from NG to LP also. There are a few other adjustments that need to be made though, the oven control valve has a small screw that needs to be turned from one gas to the other for the pilot light. We also had to turn the orifices for the oven and stovetop burners to the proper position but these adjustments were all built into the stove. You might want to verify that these kind of things are already built into the stove you are looking at.
    Good luck and keep us posted.
  7. eclecticcottage

    eclecticcottage Minister of Fire

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    Just picked up the Bengal (it's made by Floyd Wells) for $60. Two hour drive each way. Will be checking into converting to LP, it looks like it's doable, pretty easy to switch out the burners, etc. Needs a good cleaning, two of the burner grates need to be repaired, but overall it's on good shape. No bells or whistles, just a basic stove (unlike some of the Okeefe and Merritts, etc with Grillavators, peroscopes, etc)-not even an oven light. But I am happy with that-nothing to go wrong, rewire, etc and it won't use any electric! We won't have it in for a while, we've got to repair the floor in the kitchen so we'll take our time and get it all pretty.
  8. celticsam

    celticsam New Member

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    If you get information on how to convert that old Bengal, let me know. I picked up one (model unknown...no plate) that needs to be converted.


    (hopefully that is a picture of the stove...)

    Neil

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  9. celticsam

    celticsam New Member

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    OK, so here's what I am looking at doing. Having seen the cost of adding a standing pilot system, and not (so far) being able to find what size orifice tubes to use, I am looking at getting a free gas stove (people give them away all the time on Craigslist), and scavenging the entire gas system from it to retrofit onto my beautiful Bengal. The top burners from the Bengal along with the pilot already on top will be retained, but the burner, pilot and gas lines to the oven and broiler will be swapped, along with any necessary valving, ect (thermostat, safety valve, ect...) Seems to me to be mostly a matter of time rather than money, and, barring gas leaks, which are easily checked for (gas detecter and soapy water), should be as safe as the stove that donates the parts. Any thoughts or better ideas?
  10. eclecticcottage

    eclecticcottage Minister of Fire

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    Celticsam, nice stove! My tag was inside the door on the left side. I've seen that style stove previously when searching for Bengal stoves, although I think yours might be a little newer than the ones I usually find (50's era vs 40's). They were built in PA so I think they are a more regional stove (like the Detroit Jewel) vs a Magic Chef or O'Keefe and Merritt.

    We aren't sure about the valve yet, I am working on trying to find replacement burner grates and we have to tear out the floor in the kitchen to do some repairs so I haven't really gotten very far yet on converting it.
  11. eclecticcottage

    eclecticcottage Minister of Fire

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    Ok, this whole thing is peeving me off. the "valve" they sell (referenced above) is nothing more than a pressure regulator, from what I was able to pry out of the company. I can tell you I wouldn't deal with them after trying to get more info on one little part, that's for sure.

    So I'm left with a question...if this so called professional resto company is selling a simple pressure regulator and stating it will eliminate orifice changes...do you actually have to change the orifices, or just regulate the incoming pressure?? Somehow this doesn't seem right, since I imagine EVERY appliance connected to gas (either propane or NG) has a regulator that brings the WC to the correct amount inline before it. Right?

    The set up on the Bengal (at least for the cook top, haven't investigated the oven) is pretty simple. There's a central pilot with four tubes that aren't sealed to it (open ended) running from that pilot to the burners (again, open on the end). Is it possible that we don't need to change anything to use this with propane, just be sure the WC is @ 10-11?
  12. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    I don't think you wanna run 10 - 11" of Water Column thru a natural gas burner orifice.
    For the pilot, you will probably get a "candling" effect where the pilot will come
    thru the orifice & then turn upwards. As long as it still engages the thermocouple,
    it should work fine. But if you've never seen a Natural Gas burner operating with
    Liquefied Petroleum pressures, I'd make sure you stand back from the stovetop
    when you turn it on. The flames are gonna be huge in comparison, because of the
    larger orifice size & the larger burner ports. I've only encountered that combination once,
    in an NG gas fireplace that was installed in a LP environment & when I fired it up, it scared
    the HELL outta me. BIG flames.
    YMMV, but I doubt it.
    ***Others may chime in at this time***
  13. eclecticcottage

    eclecticcottage Minister of Fire

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    That's what I thought, which is why I couldn't figure out what this valve was supposed to be doing. Mr Eclectic called them today and got the same run around with no answer as I did, so I have zero trust in them or the product. Too bad we can't seem to find anyone locally that will give any info/pats/work on this "old" of a stove!

    Here is what we have for a set up-is the small white object in the center of pic # 3 the orifice? This is in the center of pic # 2, where the pilot is and the tubes that feed the burners run from. Would we be able to remove an orifice from our old stove, a vintage (1970s? 1980s?) hotpoint to use that? It has an electric pilotless ignition however (if pics would help I can get them).

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  14. eclecticcottage

    eclecticcottage Minister of Fire

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    Hm.. Ok, these are pic #3 and #4

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  15. eclecticcottage

    eclecticcottage Minister of Fire

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    Oh, and yes, parts are loose. I know how they go back together, things got jostled around moving it from the PO's house, into our truck, out of the truck, into our house. Also, I need to clean in there still.
  16. coaly

    coaly Fisher Moderator Staff Member

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    Natural Gas is used at HALF the pressure (approx. 1/4 psi compared to 1/2 psi with LP) with about TWICE the size oriface as propane. It's due to the specific gravity of the two gasses.
    There are tables to figure out the oriface size per BTU required at each burner.

    Natural Gas pressure is regulated lower (about 1/2 the pressure of LP) at the regulator in the gas valve. When converting to Propane, the regulator is blocked open to allow the system supply regulator to supply the required 10" Water Column pressure. Convertible valves have a cap that sets the spring pressure correct for Nat, and flipped over puts more pressure on the spring, actually blocking it open. Valves made for either gas ONLY are not convertible, meaning you can't change the pressure in the regulator. That's the only difference.

    Here is a gas oriface sizing chart. http://www.joppaglass.com/burner/lowp_chrt.html
    It requires numbered oriface drills, but it gives the diameter in thousandths as well. I have a set of numbered oriface drills, so never had to measure the one needed with a micrometer, but that's how you can make sure you use the correct size if you don't know the size of the drill bits you have.
    Orifaces are normally brass, and can be peened shut with a ball peen hammer (closed) and redrilled from Nat to LP. You will also find them soldered shut and redrilled. The oriface stays cold at the air intake, so this works too. It's nice to have a threaded piece of steel that the oriface screws into used as an ANVIL to protect the threads if you peen it shut. That's why many used solder.

    The air adjustment will need to be set on each burner as well to obtain an all blue flame. Yellow tips are a no no and will cause carbon deposits on pans. It's quite simple once you do it. New ranges have adjustible orifaces that come set for Nat. and you simply turn them down tight to close the hole to the LP setting. Some older appliances that were convertible had a set of orifaces screwed to the back to change to the gas being used.

    I'm retired from my own LP gas service business and this is what I did, as well as installing systems. There are now laws requiring a lable to be affixed on the appliance and signed by the installer. This identifies which gas the appliance is set up for.
  17. coaly

    coaly Fisher Moderator Staff Member

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    When sizing the pilot oriface from Nat to LP, you will find you need an extremely small hole for LP. (The pilot hole for Nat is almost the main burner hole size for Propane) Normally the correct size oriface is used, since it will be only a few thousandths. Pilot holes are cleaned with a pilot broach. It looks like a needle with fluted sides about the thickness of a human hair. They can be tapered, so the farther they are run in, the larger the hole. You may be able to peen them shut partially until you get it small enough, then true up the hole with a broach. The size of the hole is like holding it up to the light and seeing a speck of light. A dirty or irregular hole will appear fuzzy, like you need glasses. A clean round proper hole will be a speck of light. Some pilot orifaces are made by stamping with a certain letter to allow the proper amount of gas through. Changing the letter changes the oriface size. This is an art that is probably gone with high button shoes.
    Pilot broaches are so small they are sold in a vial by the dozen. They are easy to break, and can be used in a pin vise spun by hand like most oriface drills.
  18. eclecticcottage

    eclecticcottage Minister of Fire

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    thanks coaly, you just confirmed exactly what I thought. The reason I am suspicious of the valve I was referring to was this line on their site "Installing this part eliminates the need to change all of the orficies". I can't figure how that could be possible.

    If the orifice is usually brass, then I am guessing that what I thought was the orifice is not (which is actually in the middle of pic #4, because for soem reason they uploaded opposite of how I was trying to load them)...so...since I have never found another other reference to this model stove ANYWHERE and am pretty unlikely to find any diagrams or manuals-where should I be looking to find it? Is there any reason I can't or shouldn't scavange a "new" one from my old stove (we will be scrapping it, the oven doesn't work properly and it's pretty beat up and ugly-but it came with the Cottage).

    Am I correct in assuming (yeah, I know, assuming is BAD) that the "flaps" in pic #3 that are open a certain amount are the air controls for the burners?
  19. coaly

    coaly Fisher Moderator Staff Member

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    From the supply line the gas comes through the "manifold" to the stove top burner valves or oven control valve. The last thing it goes through is the oriface. Gas vapor actually pushes out the air in the "Mixing Tube" (The long tube between the air intake and oriface and burner). This is called a mixing tube since the gas mixes with oxygen in it and needs about 70 buckets of air to one bucket of gas. Atmospheric pressure pushes into the air shutter or air adjustment hole into the mixing tube and is ignited at the burner. The entire burner should stay relatively cool since the flame is actually above the burner. Incorrect fuel pressure or incorrect air adjustment can cause the flame to jump inside the mixing tube and burn at the oriface like a torch in the tube. This overheats the tube and burner and must be avoided. You will know if it does by a fluttering and roar sound in the burner.
    When you size the oriface for the BTU you want from each burner, It's best to open the air shutter about half way. Closing it will give you yellow flame tips. Open it until yellow is gone, and that should be about right. Too much air will lift the flame off the burner. (Too small of an oriface for a burner can make the flame circle around the burner and chase itself or go out). The reason for air adjustments is altitude (air density and pressure) as well as slight variations in regulator adjustment. (pressure through the oriface)

    No idea why they would say you don't need to change an oriface with valve replacement. That would be true for a stove top burner valve with the oriface attached to the valve, with adjustable oriface like new ranges. Otherwise the pressure regulator in a valve controls the pressure at the oriface, and oriface size controls the volume of gas going through it.

    If you want one burner hotter than the others, (on any range) you can always drill it out slightly more than the others and run the air wide open. As long as there are no yellow tips, you will be getting more BTU from that burner. As soon as you go too big, even with air wide open, you will still be rich and have yellow flames, so you need ro resize it down to obtain an all blue flame. When you find the largest oriface you can use and have blue flame with air wide open, that would be the max BTU for the burner.
  20. coaly

    coaly Fisher Moderator Staff Member

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    By your pictures, it looks like "cottage53" is looking at the top of the pilot oriface.

    The mixing tubes connected to burners have the air adjustment at the main oriface for each burner in the manifold. The burner tube (mixing tube) sets over the oriface where the gas comes out of the manifold. You can see the oriface looking through the air intake shutter. There is such as thing as oriface alignment; so the oriface "shoots" the gas up the center of the tube creating a good mix, but that's pretty much a part of the design of the burner tube. Centering the burner tube on the oriface is all you can do. In water heaters, where the mixing tube can be installed crooked over the oriface, you can imagine how the gas would go in crooked and mix incorrectly with turbulence in the mixing tube. Probably more than you need to know.
  21. eclecticcottage

    eclecticcottage Minister of Fire

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    Thank you! Now we just have to find orifices...and clean the heck out of it!

    Here it is in place anyway

    [​IMG]
  22. eclecticcottage

    eclecticcottage Minister of Fire

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    Question...could we have adjustable orifices? If I'm understanding everything correctly, that's what these appear to be?

    The first photo shows the needle inside of the outer brass piece which may be screwed on and off, you can see the one for the other burner on that side still on in the top part of photo two.

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  23. coaly

    coaly Fisher Moderator Staff Member

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    No idea what year they started adjustable orifaces. That point looks like the needle on a newer stove with an adjustable oriface. As you turn the oriface down to the pointed tip, if it looks like it's coming through the hole in the "cap" that is what makes the hole smaller. Normally turned down snug leaves a little opening around the tip that allows the correct amount of LP gas out for the burner.
    A dab of grease or anti-sieze on the valve threads where the cap screws down helps give you the "feel" when the thread bottoms and the oriface cap is snug where it should be. If there is anything on the threads, and it binds, you may think it's bottomed out, but the oriface is still partially open. When you screw them down, compare how much of the point sticks out of each one, to get an idea if they are turning down fully. Some get pretty tight, and you don't want to twist a burner valve off. I wouldn't say there's a trick to it, but some are worse than others. Some new ones feel like they're cross threaded they turn so hard. Perhaps they put locktite on them now to hold the Nat. position from the factory. I've had a few turn extremely hard.

    If it has adjustable orifaces, it should have a settable regulator as well. Usually in-line at the connection, the cap may say NAT on it, and when you unscrew the cap and flip it over, it was have an LP on it. This cap presses on the spring in the regulator. Natural Gas position allows the spring to go up inside the cap, decreasing pressure on the spring. LP position will be designed with a shoulder or stud on the cap that increases pressure on the spring. (increased pressure pushes the diaphram open to bypass this appliance regulator. This allows full system pressure to appliance from the main regulator at tank. If you Google "appliance regulator" you'll probably find info and pictures of different regulators. Your original question was geared towards regulators built into safety valves. (found on water heaters, furnaces .....)Is there an appliance regulator at the gas connection on this stove? That is where the regulator normally is on kitchen ranges. The supply line goes into the regulator first.

    If there is a pilot adjustment on the pilot line before the pilot oriface, you may be able to turn it down, and use the same pilot oriface. This adjustment screw in the lin ecan also be used to shut th epilot completely off. Not all ranges have them, most older ones do.
  24. eclecticcottage

    eclecticcottage Minister of Fire

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    Awesome...

    As far as a regulator goes, I think someone disconnected the line after it, I've never seen an appliance with a hook up starting inside of it like this one (pic to follow). We do have a propane regulator in the supply line that we disconnected from the old stove.

    Is the adjustment screw for the pilot the one in the second pic?

    THANK YOU for helping with this:cool: Every place I've contacted locally pretty much runs when I mention the age of the stove. The way it's built with no bells or whistles, once we get it going we should have it forever, unlike the one we had at our old house that SUCKS. Now to find a matching fridge :D

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  25. coaly

    coaly Fisher Moderator Staff Member

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    You're OK with the correct pressure from system regulator. There is no regulator on your stove to cut it down for Nat. You will already have 10" W.C. at the stove connection to burner oriface from your system regulator.

    As long as the line shown with the adjustment screw is the pilot line, yes that's the pilot adjustment. It may branch off and supply the oven pilot as well. Not all older stoves have a oven pilot. Some are match lit every time, and when the oven comes up to the temp set on thermostat, there is a bypass in the thermostat that when it closes the main flow to oven burner, it bypasses enough around the Tstat valve to reduce to a very small flame on main burner. This is better than a pilot since the small flame maintains temperature better than shutting down completely. But this is usually on commercial stoves.

    Another use for that scew is doing a leak down pressure test. First you shut off the pilots with it, and remove one stove top burner. Normally a manometer is put on the oriface from removed burner. (rubber hose fits over oriface end with burner removed) Gas is turned off at the tank, and burner valve connected to meter is opened. This shows system operating pressure. By relieving pressure at another top burner, when meter starts to drop, the bleed burner is closed, and the meter must hold the test pressure for 10 minutes. This leak tests the entire system including all fittings on stove without soaping everything.

    There's no reason for appliance service companies to shy away from old stoves other than parts availability. (and not being familiar with them, since they probably learned on newer appliances) The basics are still there for combustion and flame control. I prefer the older ones since they have more adjustments on them, and no electric is required.

    Yours may have a simmer burner as well. You will know by removing the knob. If there's a small screw on the end of the shaft under the knob, that is the adjustment for setting the gas flow on low. With it lit, you hold the shaft from tuning on low. Running the screw in will decrease the flame down to little dots. A true simmer is blue flames that do not go above the rim of the burner looking across it - eye level with the burner top. When a stove is in a drafty location, many times the simmer adjustment is raised to keep it from blowing out. Most people don't know there is a low adjustment on good ranges. Many new ranges will have one designated simmer burner with this adjustment screw under the knob.

    Imagine the looks I'd get if I asked questions at a gas or appliance place about the equipment I work on ! Antique chicken brooder heaters, amonia refrigeration powered by gas or kerosene, and propane toilets !! (they are stainless toilets that you clamp the lid shut, fire on propane and dump the ash from a tray) I've built some LP Gas burners to heat locomotive wheels to change tires too. A loop the size of the wheel that uses 10 psi. This was common knowlege years ago.

    The oven burner is going to have the same type adjustable oriface that admits the gas into the burner tube. Since they run hotter than the stove top burners, they can be stuck and need PB Blaster or WD-40 to loosen first, then grease the threads and turn down snug for the adjusting pin to close that oriface as well. (very little grease on the threads only so it doesn't plug the oriface hole) Again, no yellow flames or flame tips. All blue by setting air adjustment. If you can't get the yellow out, the cap s probably feeling tight on the threads and not closed fully on the pin. Usually a 1/2 inch wrench cautiously turned a little at a time until just snug. It's easy to overtighten with a big wrench. Don't use a big adjustable. Small open end wrench only on oriface caps. Valves and caps are soft brass.

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