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Featured Propane heater behavior

  1. Apr 24, 2018 #1

    DaveC426913

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    I've asked a related question before, but this is new.

    I have one of these propane heaters:
    tt30cdgp.jpg
    As months go by, it has an increasing habit of spazzing out.

    It will frequently do this in a strong gust. But with even a little wind, and more often when it is set on low, it will spontaneously and startlingly begin screaming like a rocket engine. When it does so, the mantle immediately starts cooling.

    It does this in one heater more than the other, so there's definitely some factor internal to the device, not just wind or fuel level.

    It will occasionally spontaneously stop doing this, but sometimes I have to shut it off (by nudging it so it's anti-tilt safety mechanism activates, cutting off fuel.) I can always reactivate the fuel, and, if it's still hot enough it will auto-ignite and continue to heat up back to normal.

    Obviously, something is happening to the position of ignition prior to the mantle, causing it to still burn (albeit very loudly), not to heat the mantle properly.

    Let's pretend you've already suggested that I
    a] take it apart and clean the nozzle parts, and/or
    b] not mess with the mechanics of compressed explosive, flammable fuel delivery.

    What is happening when it goes into this rocket engine mode? Is the "ignition front" moving back from next to the mantle to some other point farther inside the fuel feed?
     
  2. jcsd
  3. Apr 24, 2018 #2

    berkeman

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    Is it outside?
     
  4. Apr 24, 2018 #3

    Tom.G

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    Here are a few similiar instances I've run across:
    • Something similiar happens with Oxy-Acetylene welding torches, even (especially?) with brand new tips. The usual cure is to run a cleaning burr thru the holes in the tip. (the burrs look like an assortment of wire feeler gauges but are actually round files)
    • Another possibility is that the backside of a mantle is damaged or dirty causing a later flame front and sudden ignition (explosion?) of the incoming fuel.
    • With lower pressure gas flames, a partially clogged nozzle or a too high inlet pressure will push the flame away from the nozzle with some audible turbulence
    Maybe check the pressure regulator, or artificially reduce the pressure by partially closing the tank shutoff valve to see if that makes a difference.

    Cheers,
    Tom
     
  5. Apr 24, 2018 #4
    Which burner element is affected more ... the one closer to the hose connection, or farther from it?

    Edit: Does it do this more often when propane tank level is low rather than when fitted to a full tank?
    Is this a Dyna-Glo model TT30CDGP?
     
    Last edited: Apr 24, 2018
  6. Apr 25, 2018 #5

    ChemAir

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    Two things I've not seen mentioned:
    1) One thing I'd check (you probably already have) is the orientation of the air mix adjustment. On this type heater, it is usually right between the safety start solenoid and the burner. Usually a swivel collar with a couple of holes over a fine screen make this adjustment. Sometimes it either moves, or can get trash in it. This may need adjustment.
    2) Propane tanks have excess flow protection that *sometimes* doesn't work very well, or maybe works too well. Normal procedure is--tank valve has to be off first with other valves off. Tank valve on, then light burner. If the tank valve is opened with a burner open (don't think you can do this with this type) the excess flow protection will restrict the max flow out of the tank, and it will be less than what the heater can use, and it will be erratic/unstable. I'd exchange the tank if the other suggestions don't help. I have seen some of these that just wouldn't work right, and the gas volume never would get to where it should be. It was always low.

    Usually, performance deterioration over time is like @Tom G suggested, slow plugging of orifices by minute bits of debris, usually corrosion products or insect/spider parts. I wouldn't leave out the other suggestions, though.
     
  7. Apr 25, 2018 #6

    DaveC426913

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    Thanks guys.Wow! I came to the right place.

    Yes. But under a deck roof, so protected from weather.

    It has a primary flow valve off the tank with 3 settings. It is worse on a low setting than a high setting.


    It started with the one nearest the flow. I can't even use that one now. It's now doing it on the other one.

    Worse when low.

    Not sure, but it's virtually identical to the one in the pic.

    I'l give it a clean. Presumably 'adjustment' means it might need to be opened a little, as opposed to closed.

    I've encountered this, yeah. If I don't tighten the connection enough, I get almost no flow. PRetty sure this is not the problem.

    Thanks, I'll scare up some pipe cleaners.
     
  8. Apr 25, 2018 #7

    Tom.G

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    Don't be surprised if they don't do much. Any debris in the orifices will be well carbonized.
     
  9. Apr 25, 2018 #8
    The same type of cleaner used to maintain oxy-acetylene torch tips may prove useful. Pictured is a Hobart #770084, and it (or it's functional equivalent) ought to be available from local shops that deal in gas welding supplies. This model has 12 round cleaning files spanning a range from drill size 49 to 75 (0.073" to 0.021"; 1.854 mm to 0.533 mm).
    Tip cleaner.jpg
    Edit: Reading through the thread more closely, @Tom G had already mentioned them.
     
    Last edited: Apr 26, 2018
  10. Apr 25, 2018 #9

    DaveC426913

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    Thanks. I might just put the cost for that cleaner toward buying another heater. They're about 60 bucks.
    But considering the season, I might just wait till autumn. :smile:
     
  11. Apr 25, 2018 #10
    Reason I'm asking ... there is at least one mention of a similar symptom in the Amazon critical reviews for this model, for instance,
     
  12. Apr 26, 2018 #11

    Averagesupernova

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    My experience with those types of propane heaters is that unless it is a Mr. Heater brand it is not worth bringing it home
     
  13. Apr 26, 2018 #12

    DaveC426913

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    Huh. Good to know. Thanks Asym and Aver.
     
  14. Apr 26, 2018 #13

    Averagesupernova

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    Mr. Heater does some rebranding. They are not manufacturing all of the stuff that has their name but I have found their stuff to be more reliable than others.
    -
    Thinking about this more, I have found similar symptoms to what you describe on a near empty tank. I don't know what the minimum inlet pressure is on the regulators that these heaters use but I suspect that they are made to be safe but that's about it.
     
  15. Apr 26, 2018 #14

    DaveC426913

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    I've seen it running right until it runs out of gas and the flame dies.
     
  16. Apr 27, 2018 #15
    I've been wondering whether a subtle interaction between wind gusts, low burner temperature, and how the gas safety valve operates may not be implicated. Haven't found specifications on how this safety valve operates, but along the way found a resource chock full of related information that's making for an interesting read.

    "TECHNICAL FEASIBILITY OF A CO SHUTDOWN SYSTEM FOR TANK-TOP HEATERS", United States Consumer Product Safety Commission
    https://www.cpsc.gov/s3fs-public/tanktop.pdf

    Tanktop_Rsd_Heater_Figure2.jpg

    I had been envisioning a burner head similar to that of a stove burner placed behind the screen, but thus drawing suggests otherwise. Is this more like how your burner is?

    TankTop_14-13Pct_O2.jpg

    Does the flame have a significant amount of blue to it as shown in the above pics?
     
  17. Apr 28, 2018 #16

    DaveC426913

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    That is an exact representation of my burner.

    No, it does not have any blue. It's all bright red, until it goes splah, then the glowing red goes away and I hardly see any flame. (even in the dark, so the blue should be noticeable.)

    It does however, start melting the dish pretty quick.
     
  18. Apr 28, 2018 #17
    Should I take it that the dish is aluminum?

    Can you tell if the gas safety valve itself is making any noise (in addition to the rocket engine scream)?
     
  19. Apr 28, 2018 #18

    DaveC426913

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    I lie. It doesn't start melting quick. It only did that the fist time, when I let the thing run for minutes, thinking it was doing no harm. After I saw the melting, I now always kick it off right away.

    Also, now that I think of it, it's not the dish that started melting, it was the housing (the 'plenum' housing in your diagram).

    I'm not gettin' my face near that.
     
  20. Apr 28, 2018 #19

    Tom.G

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    Ahh, that's a big clue!

    That Burner Head Screen exists to keep the flame out of the plenum. Maybe you recall a demonstration in High School physics or chemistry class with a Bunsen burner and a metal screen. Rest the screen on the burner and ignite the gas. With the screen resting on the burner, there is a normal flame. Raise the screen and the flame rises with it, never returning to the burner orifice.

    What is happening in your case is, for whatever reason, there is enough heat conductance to the plenum side of the screen to ignite the fuel in the plenum.

    Some possible root casues:
    • a hole in the screen
    • screen mounting loose
    • contamination conducting enough heat thru the screen for ignition in the plenum
    • borderline design of the screen being too coarse

    Hope this helps.

    Cheers,
    Tom
     
  21. Apr 28, 2018 #20

    Averagesupernova

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    Yep. The fuel is supposed to burn on the mantle which in the pic is referred to as the burner head screen. I believe it is a ceramic perforated surface. Maybe the cheaper units are not ceramic?
     
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