Convert NG to LP 1950's stove

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,340
NE PA
Can't read the tag. Does it say for Natural only, or is there a box to check for Propane?
Is the BTU for top burners and oven readable on tag?
Do you have a manometer or U-tube gauge?
Remove an orifice for top burner to see if the valve has an open hole for gas to come through, or if there is a tip of a needle sticking out of the valve that will go into the orifice and close the hole as the orifice is turned down the threaded part of valve farther. That would be an adjustable orifice that makes it relatively simple.
If no needle, you will need to size the orifice yourself. I can walk you through that procedure, but if you have no BTU rating on the tag, you will need to measure the orifice you have to calculate the BTU currently for Nat. and keep it the same BTU or close with the LP size. This will take a set of orifice drills to measure the existing Natural orifice size. (Use the chart I linked to on post #46) The cost of a manometer and orifice drill set is far more than having it converted unless you already have those tools.
Lastly, is the appliance connected to an existing LP supply system? Or are you the supplier with your own cylinder and regulator?

There must be a service valve at the other end of appliance connector shown in the first picture. Keep that valve shut off to prevent gas flow into appliance until a manometer or U-tube gauge is connected to leak test entire appliance after converting. This assures the entire appliance has no leaks as well as all pilots and burners have no flow by completing a leak down test. If you're not familiar with leak down testing and equipment, you may be able to size the orifices yourself and have the supplying propane company (if there is one) leak check it for you.

Depending on the supplier, they will probably require a pilot safety valve to be installed. That is the push and hold type safety valve to light pilot. No gas can go through the thermostat to oven burner without the standing pilot being lit.

Any supplier should require an oven safety valve that can only open when pilot is lit, or pilot heat activates main burner. This prevents gas flow into oven burner without a proper pilot to ignite the oven burner.
 
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Woodchuckinn

New Member
Oct 5, 2018
4
Long Island
Thank you @coaly! I should have included more details in the original post.

The tag was in bad condition, so unfortunately it doesn’t help much. The tag has a spot that says what the stove is setup for. It is stamped NAT.

The stove was connected to natural gas in the city and was working fine, I assume without leaks, until it was disconnected. All I’ve done is clean it up. I wasn’t really worried about leaks because it was being used regularly.

I don’t have any of the special tools you mention. Also, I don’t have a propane provider. I just have a gas line that is attached to a small Blue Rhino type tank. This was working fine with the previous newer Home Depot type stove that was here when we moved in. I can go see what that attachment looks like. I guess there is a regulator there.

The great news is that the orifices do have a needle sticking out so I plan to tighten them down to close the produce size.

I should just tighten them all the way?

Is there anything else I need to adjust?

Thank you for all the help!
 

Woodchuckinn

New Member
Oct 5, 2018
4
Long Island
I’ve tightened one orifice, to see how the needle/cone will sit inside the hole. There are more threads left, but I didn’t want to over tighten them. It looks like (from what I can see) that it completely blocks the hole... is that right?

Here is a close up of the two orifices, the right one having been tightened down.

Also, here is a picture of the tank and regulator setup.
 

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,340
NE PA
I assume that cylinder is NOT indoors, it must be outside, never inside any building.
The regulator on the cylinder is not a 2 stage regulator which is required on any automatic operated appliance. (oven) The type you have is called a Bar-B-Que regulator which is only for manually operated appliances such as an outdoor grille with no thermostat. You need a 2 stage regulator by code.

Not sure why there is a service valve on supply line near cylinder. It is not required. That type valve needs to be at the supply line where flex connector connects to supply line.

Just tighten orifice until snug, don't over tighten. It should be metered through the needle. You can test it for flow by removing valve and blowing through valve with it "on".
Same as oven burner as long as it is the same type.
That takes care of sizing the orifices for Propane.
Next is pressure and pilots.

Close all pilot adjustment screws until snug, again do not over-tighten.
I can't see the pilot adjustment for oven in your pictures. It should be on the thermostat housing where pilot line comes out of T-stat., but some are an inline tiny valve with screw shut off / adjuster.

With pilots lines connected and burners installed on top, this completes the range top burners.

The oven burner is more complicated. You have not posted any pictures showing a safety valve of any type on the appliance. I suggest a propane service person or propane company install a safety valve that prevents the oven thermostat from passing gas through the oven burner orifice when there is no flame present at pilot burner. It is beyond the scope of explaining what you need without the full understanding of how a safety valve with electromagnet powered by a thermocouple works, and knowing the exact parts you need without having the appliance in front of me. A picture of a safety valve is shown in post #42 of this thread. (with red button) The original poster was able to do their own conversion since their appliance had the required safety equipment. The problem with yours is IF the pilot were to go out when the burner shuts down. (oven up to temp, burner shuts down. There are reasons for a burner to light or shut off abruptly, extinguishing pilot due to lack of oxygen to the pilot burner. Oxygen is actually consumed by the "pop" of abrupt ignition, and now you have an open burner with no pilot flame. A safety valve shuts gas off to thermostat eliminating this very dangerous condition) So as the temperature in oven drops, and thermostat opens, gas flows through oven burner. NO pilot light present allows gas to build up in oven until one of the stove TOP pilots ignites the oven. Since propane is heavier than air, most drops out the bottom until something else in the home ignites the oven. You can imagine you would not want to be in the same building when the oven or entire room lights explosively. That is why all gas appliances now require this safety equipment.

The leak check is not only for leaks from moving an appliance, but also to be sure there is no gas flow coming out of a pilot or burner before lighting anything. The procedure is to put a tee in the line for testing AFTER the service valve so when on, it reads system pressure to the appliance. The service valve should have a test port, but if not, a test Tee is used to tie into the system. With all valves closed and ALL pilot adjustment screws closed, the entire appliance from service valve to every orifice is being pressure tested. By shutting the service valve off, residual pressure is bled off until gauge starts to drop quickly showing even a very slight pressure drop. It then must hold pressure 10 minutes with no drop. If a pilot were on, pressure would drop off almost immediately showing you don't have a sealed system, so you would not attempt lighting anything on or near the appliance. Once you know there is no gas flow, you turn on the service valve, then holding a match to a pilot, slowly open the pilot adjustment screw. This is the only pilot burner that would light since you know you have no flow anywhere else. Obviously the pressure test leaves no guessing that any gas is coming out anywhere. Without a proper leak down test, you could be working on an upper pilot or burner and go to light the oven which has had gas seeping from a pilot or burner. So obviously there is no danger when you know it held pressure. The gauge doesn't lie, (but you need to know how to use it!) you can't soap every inch of every line, and you wouldn't want to spray soapy water into each pilot to look for bubbles. An open pilot would blow the soap off without bubbling anyway. A pressure leak down test is the only way to safely retire after doing this for 25 years.

There is much more to leak down testing and converting which takes days or weeks of training through propane suppliers such as how to read a gauge drop. As an example, think of pressure on a gauge as how much water is in a bath tub. When letting water out of a full tub, the drop of water is not noticeable. That is how a drop looks on a gauge with a lot of pressure. You can't see it. Now as the water is almost out of the tub, the last gallon or quart looks like it is moving very fast. That is how pressure drop works on a gauge as the pressure gets lower. It is more noticeable, yet the same leak is still there just as the same amount of water was moving out of the tub when full. Just buying a manometer doesn't mean you know how to use it without proper training.
 

Woodchuckinn

New Member
Oct 5, 2018
4
Long Island
Ok, thank you again. I really appreciate the time and advice. I’m going to call the local propane company and have them come out to pressure test and install the safety valve. I’m gonna pick up the two stage regulator myself. This one should be good right?
 

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,340
NE PA
Yes.
See, when you have single stage regulation, a regulator has to go from cylinder pressure which can be anything from 1 or 2 psi to the relief pressure set at 375 lbs. That is asking a lot to control that much of a pressure difference in one decrease down to 1/2 psi. Having one regulator section that decreases to 10 psi (first stage) means it will be keeping the pressure close to 10 from cylinder pressure of 10 pounds up. As an example, if 100 psi is controlled down to 10, and 200 psi is controlled down to 11 and 300 psi is controlled down to 13, the second stage is capable of regulating 10 to 13 psi down to 1/2 far more accurately than 300 down to 1/2. Pressure in the cylinder varies that much by temperature. So the more stages of regulation, the more accurate it gets. With water, you could have 500 to 400, to 300, to 200...... all the way down to the last set at 35 lbs keeping it very steady no matter the flow.
Regulators also have different size orifices inside where the needle goes into the seat which opens and closes. This size of opening is what determines the BTU capacity of the regulator. Too small of an opening will freeze up, stopping flow if you are allowing too much though a regulator with not enough capacity. So sizing is critical for the BTU max. expected to go through the regulator.
 

kmagill

New Member
Feb 10, 2019
1
Colorado
Hello! Desperate need of assistance and this thread hopefully will provide some answers... @coaly I’m hoping for your expertise on an old gas stove we picked up to go in a off-the-grid little cabin. We believe it maybe a 1930's American Stove CO Reliable 3 burner gas stove. We were told it was set up for propane it had an old regulator that hooked up to an old ID threaded tank and copper pipe that connected the stove, leaked bad everywhere. We reviewed many articles and note the orifices were never changed because they are too big.
We don't believe there's pilot light - nor a thermostat, unless we're missing something?

We think we need new orifice's (they aren't adjustable on stove - no pin seen when orifice was removed).
We measured the orifice size using a drill bit and 1/16" drill bit slide through loosely.
Following are the questions we have...
1/ Orifices & BTU's - don't know what the BTU's are on the Original orifices but based on conversion table 1/16" = 0.0625 do we simply do math based on 4.0 Natural this would be ~ #68 orifice? Does that seem right and where do you buy these special size orifices?
2/ Oven orifice - no idea, we removed it and it has an outer 1/4" opening that narrows inside to less than 1/8"...maybe 3/32"? or 7/64" hole, any ideas on what we should replace this with?
3/ Regulator - without a thermostat, what kind of regulator do we need? is the propane tank house regulator sufficient? or do we need a 2 stage regulator?
4/ hook up to stove - we bought CSST pipe and the 1/2" fitting works, plan to run this through the wall to connect to propane tank hose outside. Can we simply connect to a standard propane tank flex house with the built in regulator?

/ Stove.jpg Burner Burner Control Knob w/ orifice Control Knob.jpg
Orifice close up Orifice.jpg Regulator that came w/ stove Regulator.jpg Regulator side view 2.jpg Regulator side view.jpg
Oven Inside of oven.JPG Oven Orifice Oven orifice.JPG Gas line into Stove.JPG Gas line into stove 2.JPG
 

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dvd545

New Member
Feb 11, 2019
1
07092
Hi @coaly
Wow! what a wealth of information already on this thread. Your quite the expert when it comes to these LP stove conversion proccess.
I have an old Caloric stove that was run on natural gas. I am trying to convert it to LP however I have come up completely dry with any information regarding converting it. I purchased a propane regulator and hooked it up to a propane tank hoping that I might get lucky but unfortunately it seems the orifices are way too big. The flames were gigantic. It also doesnt appear that the orifices are adjustable. (no pin)

The orifices have a number 30 printed on them. Do you know what that might mean?
How do I size the correct BTU's for these burners?
Also how would I adjust the flame on the oven portion? Is there a orifice somewhere inside the thermostat control?

Attached are some pictures of the stove, hopefully that will help.
Looking forward to your reply!
Thanks in advance.

20181230_193524.jpg 20190125_204244.jpg 20190125_204609.jpg 20190125_204617.jpg
 

o0oo00o0o

New Member
Nov 14, 2021
1
New York
Hi. I could use some help from @coaly. I’ve got a Wedgewood that I think is from the 50s. It’s a dual wood/gas setup, and has a gas griddle in addition to four gas burners.

CC6974E3-7C61-41A3-8A15-67127954C2C5.jpeg

It came to me set up for natural gas, but thanks to the advice you gave @eclecticcottage, I was able to tighten down the burner and oven orifices for LP. As for the pilot screws, they seem to just turn and turn, without loosening or tightening no matter which way I turn them. For the burner pilots, I was able to use a wrench to hold a nut on the bottom side of the screw going through the lines and then turn the screw tighter. Have you seen this before, and if so, did I do the right thing? As for the oven pilot, it’s set up differently. It just turns and turns. See my photo below.

image.jpg


My oven also has a safety valve:

image.jpg

There are no NAT/LP labels anywhere—including behind the thermostat knob, which I took off to check—so I also wanted to know if there’s anything else I need to adjust besides the orifices and the pilot screws.

Last question: this is the line that will connect to the LP line that comes in from my tank outside.

image.jpg

I am serviced by a propane company, and like others have mentioned, they took one look at the Wedgewood and told me they weren’t sure how to convert it, but once I did it myself they’d happily hook it up for me (which is basically telling me they refuse to help, because hooking it up to the line is easiest part!). I’m not sure I have a regulator for my current stove, which is a pretty new Hotpoint (like less then 20 years old). Currently the LP line connects right to the Hotpoint via a flex line. I would need to buy a regulator to connect to the pipe coming from the Wedgewood, correct?

Is there anything else I need to do for the conversion? Thanks!
 

DAKSY

Full Time RVer
Staff member
Dec 2, 2008
9,079
Wherever we're parked
I'd say you're gonna need to change the valve or at least the regulator head. It might be best to pull the valve so you can see if you can find some identification on it. Maybe then we can research what needs to be done.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,340
NE PA
Pilot screw (oven in-line) is probably open when the slot is with the pipe, closed when the slot is across the pipe like a quarter turn valve. They will keep rotating and not made to screw open or shut. If you do a pressure test, try turning the screw slot across the direction of flow to see if that stops flow and the appliance holds pressure before lighting. Then crack the pilot adjustment screw to watch for pressure drop showing you have flow.

Sounds correct for burner pilots having a seat type valve to turn closed.

The pressure is regulated by the low pressure regulator or supply regulator at the source. The adjustable regulators added on the appliance cut the pressure down to about 1/4 psi for natural using a spring inside and are actually blocked open in the LP mode to use full system pressure from supply regulator.
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,340
NE PA
If the oven thermostat doesn’t have an adjustment to set for Nat or LP, that should be it as long as the oven main burner orifice is sized correctly for the btu rating of the burner. You can tell by the orifice size that was there if it was sized for Nat. Just use the same btu size orifice for LP to match the original Nat. size output. It should be all blue with only minimal yellow tips when correct.