Wow! What a gas odor!

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Old 11-23-14, 03:18 AM
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Wow! What a gas odor!

This is about a very old (80 years) cast iron stove - a Glenwood Duplex - that was overhauled and converted from natural gas to propane, with new orifices.

The cooktop burners work OK (so I think the regulator is properly installed and the new orifices are the proper size) but the oven is trouble. It gets to temperature OK, but it emits a powerful odor, which the top burners do not. The odor seems strongest when the oven is working on high. (There are two operational levels: high when it's bringing itself to temperature and low when it's maintaining temperature.) I've done the best I can at cleaning out the oven burner (with a vacuum cleaner), as I did with the top burners, but the oven odor persists. I've tried adjusting the air shutter in both directions but that seems not to help.

Does this indicate incomplete combustion, possibly because the orifice may be the wrong size? Should I try a different orifice? With the hole larger or smaller?

Could it be that the burner still has deposits of some sort inside? In which case, is there a way to clear them?

Anything else I should consider?

Many thanks.
 
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Old 11-23-14, 05:32 AM
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There are two orifices. NG and LPG. Make sure yours has the LPG. The odor could be from incomplete combustion. Has the stove been in the house for 80 years or stored outside for any period of time? Did you dismantle all the shelves, drawers, etc to clean it? I'd hate to think you were slowly cooking a petrified possum.
 
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Old 11-23-14, 06:29 AM
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These are plain orifices that are drilled out to make the proper opening. Oven orifice is same as top burner orifices but a different size hole. The guy who made them for me said he was taking the sizing from a table that indicated which size goes with which size burner (according to no. of BTUs). I agree that incomplete combustion is probably what's going on, but I don't know if I should experiment with the size of the orifice hole - I don't know if the size of the hole would affect the combustion in a way to produce the odor.

No, the stove was stored in a garage for four years. It was then completely dismantled, cleaned and converted to propane. The possum was removed at that time. I understand possum is delicious but this one was overcooked.

No, really, the insides were well cleaned. As I said, I did what I could with the burner's insides by shaking it and tapping it to remove any loose particles and then vacuuming them out multiple times. It seems to me it's probably OK in there because the burner does throw decent flames and the oven does get to proper temperature, which is why I thought - as a non-expert - that I probably should consider the orifice the culprit. I just don't know if the wrong size hole is the issue, and if it is, in which direction.
 

Last edited by nugmebot; 11-23-14 at 06:30 AM. Reason: typo
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Old 11-23-14, 06:58 AM
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Hello nugmebot. Welcome to the Gas Appliances topic.

Does this indicate incomplete combustion?
Yes. The burner is likely over gassed. Flames to large.

Should I try a different orifice? Not yet.
Try an adjustment first to lessen (smaller) flame size.

With the hole larger or smaller? LPG orifice is Smaller hole size.

First try this: Adjust (close) the existing orifice to obtain a smaller size flame. Flames should only extend to within one inch inside the width of the flame spreader, which is on top of the burner. Burner flames must not lick over and up wards on the flame spreader. Must be one inch or so inside from the outer edges of the spreader.

Oven and broiler burner adjustment:
Flames should be not more than one inch from the outer edges of the flame spreader. The flame spreader is the flat plate the sets on top of the burner tube. Adjust the orifice in wards or out wards until the flame tips are about 1 and 1/2 inches to 2 inches in wards from the outer edges of flame spreader is ideal.

If the flames appear yellow or have yellowed tips, adjust the air shutter on the burner just above the orifice to allow slightly more air to enter. But not so much to cause flames to lift off of the burner and blow out wards with force.
 
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Old 11-23-14, 08:23 AM
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You say "Adjust the orifice in wards or out wards...."

Does this mean just screw it a few turns on or off? I don't remember for sure, but when I installed the orifice I probably screwed it on as far as it would go, figuring that's what one does to avoid gas leaks. Was I wrong? Would screwing it on too far cause incomplete combustion? If that's so, I certainly will try backing if off a couple of turns. I just don't want to end up with a leak if that's a possibility. Except for the air shutter, there's no other adjustment possible on these orifices. I don't know if there are other types, but these - the stove is 80 years old, don't forget - are basically like a thimble with a hole in the end.

Thanks very much for the help so far. Much appreciated.
 
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Old 11-23-14, 12:02 PM
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If you screwed the orifice ON all the way in wards and the flames are still to large, the hole in the orifice is too large. It's all about flame size. Turning and adjustable orifice in wards (tightening it) reduces the flames size. However, not all orifices can or are adjustable.

Would screwing it on too far cause incomplete combustion? Answer is no. It would cause flames to be to small if the orifice is even adjustable. Not all are. Flames to large? Then hole in orifice is to large for the burners rated BTU size. All in knowing what the burners BTU rating is. That info should be on the info plate installed by the manufacturer.

Bare in mind it has nothing to due with leaks. All to do with the ability to adjust a flames size. To large a flame, when oven is heating up to temp and burner is fully on before lowering the flames size to maintain temp is the point where determining flame size.

I am very familiar with the older appliances and serviced hundreds (thousands...) over the many years. Bare in mind relaying such info here in text only format sucks...
 
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Old 11-23-14, 12:56 PM
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This is really beginning to be helpful, but....

When you talk about a flame spreader, do you mean a plate that is over the burner and just a little bit larger in both dimensions? This oven has nothing like that. The burner is a rectangular pipe about 4 x 11 inches with holes along three sides. There's a solid sheet metal shelf that slides in directly above it, the same way the oven shelves slide in higher up. That solid shelf covers the entire width and depth of the oven. So it's impossible to measure flames the way you're suggesting.

I installed this stove some time ago. Because of the odor from the oven we've used the top burners mostly. I don't remember exactly what I did - I did everything on advice from helpful advisors - but if you think that the flame must be too large if it's producing an odor, perhaps I should try to tighten the orifice further, and if that's not possible I guess I should replace it with one that has a slightly smaller hole. Does that sound like a reasonable approach or can you think of anything else to do? Incidentally, there is no mfr's plate attached to this stove - it's from 1934, when I don't think they did such things.

According to my notes from the overhaul and installation, the top burners are 7,800 BTUs, which indicates a #66 bit for the orifices. The oven is 15,000 BTUs, thus a #56 bit. If those sizings are correct, I'm wondering if maybe this oven is actually less than 15,000, and thus the guy who supplied the orifices made the oven burner orifice the wrong size. Or if #56 is correct but he accidentally overdrilled.

I take it the air shutter, which may control the color, wouldn't have much to do with any odor.

Ah...I just checked the air shutter. It's about wide open. The flames on the cooktop are nice and blue, but the oven flames - last time I had it on - had more yellow/orange when it was heating up; at maintenance level the flame was better blue and without the bad odor. Does all this tell you something about the orifice opening, perhaps? If there's yellow with full air entry, what does that indicate?

Thanks again.
 

Last edited by nugmebot; 11-23-14 at 02:04 PM.
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Old 02-14-16, 09:21 AM
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Help! Antique stove still has an oven problem.

To get back to it, if I may: This is a now 82-year-old Glenwood Duplex, a great old hunk of cast iron, which ran for years on natural gas and has been converted to propane. The top burners are OK. The oven has two speeds: high when it's working to reach temperature and low when it's just maintaining temp. At high, the odor - presumably incomplete combustion - is unbearable.

At low - maintenance - the flame is a good blue throughout; I don't see the yellow tips people talk about with propane. At high, the flame becomes higher (of course) and lazy, and there is a fair amount of what to me is orange - and this is with the air shutter fully open.

There is no plate above the burner - just a solid shelf the full width of the oven interior - so I can't judge flame size in the classic way. There's a serious black deposit on that shelf over the burner, directly above the pilot, so perhaps the pilot assembly needs more cleaning. I've cleaned the burner as best I can.

As a total amateur, all I can think to do is try a smaller orifice. Does that seem reasonable?
 
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Old 02-14-16, 09:42 AM
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As a total amateur, all I can think to do is try a smaller orifice. Does that seem reasonable?
Yes..... the smaller orifice IS for propane and the larger one is for natural gas.
 
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Old 02-14-16, 01:03 PM
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Right - I know that propane calls for a smaller orifice than natural gas. That's what was installed for the conversion. I'm trying to determine whether the orifice I'm using might be not small enough. I don't know if the symptoms I describe indicate that my problem would be an orifice opening that's still larger than it should be.

Thanks.
 
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Old 02-15-16, 06:21 AM
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Hello: nugmebot

The flame spreader is the slightly V-ee shaped plate that attaches on top of the burner with a wing nut. Used to spread the flame out more equally and wider. The burner flames should not exceed the ends of this plate. Be in wards about an inch or so but never larger then the plate.

If the flames do exceed the flame spreaders size then the burner is over gassed which creates odors of unburned gasses like you're smelling. Very very likely the orifice size was drilled to large if flames exceed the size of the flame spreader. Also indicates orifice is non adjustable if drilling out was done. Only solution is to install an orifice drilled smaller.

Side note possibility. Lack of air flow for combustion. Be sure air ducts under appliance are clear and free of obstructions like dust, etc. Same applies to oven vent system. Both inside oven and outside ducts or vents in either case. When oven door is closed, flames maybe suffocating as a result of reduced air flow in for combustion, etc. Hot air vents venting out must also be cleared to allow free flowing exhausting.

Hope all above is clear and makes sense. Not always easy to put causes and effects with corrections into words.......
 
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