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C7 xmas lights too hot for tree?

  1. Dec 5, 2016 #1
    My wife likes the old school bulb look so I picked up some C7 string lights for the tree. This year we got a real tree. I plugged the light string in and after a few minutes the bulbs got so hot I couldn't touch them. Are these things really that safe and ok to put around a tree? I must imagine they are insanely inefficient.
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  3. Dec 5, 2016 #2


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    They'll probably be fine (although if it was me I would be hesitant to leave them on unattended, but that's just me [they really should be fine]). Like any incandescent bulb, they become too hot to touch them. But they shouldn't light the tree on fire. Ensure your tree ornaments are not made out of flash paper or explosives, of course.

    The inefficiency is insane though. They're kinda like a bunch of little tiny space heaters.

    If it's not too late, they do make C7 shaped LED bulbs, btw. They look like C7 bulbs, but they're really LED powered.
  4. Dec 5, 2016 #3


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    I'm not sure which kind of bulbs you mean. But it sounds like you're on your way to a possible first class fire, once the tree is dry and only the essential oils are left - combined with an extraordinary large surface. The bulbs here are usually formed as small candles and don't get hot enough. However, the classical Christmas tree fire is ignited by candles, so I assume it might be enough to avoid direct contact with the needles, such that the heat cannot directly act a long time on the same spot and air is still a little of an insulator. And firefighters here normally recommend in the weeks before Christmas to place a fire extinguisher near the tree.
  5. Dec 5, 2016 #4
  6. Dec 5, 2016 #5
    No doubt, when lit the tree was giving off noticeable heat!
  7. Dec 5, 2016 #6
  8. Dec 5, 2016 #7


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    Looks pretty hot, indeed. Ours look like these: http://i824.photobucket.com/albums/zz168/flimflam555666/lichterkette1.jpg
    and the modern ones are all LED.

    Here's what I've found on a fire department's page, but these guys are notoriously cautious.

    "Since the Christmas trees are chopped by end of November, and no moisture is left for 3-4 weeks, the plant tissue dries out and becomes increasingly flammable. If these chambers filled with resin are heated, the resin first liquefies and evaporates as a result. The pressure thus created blows up the needle. The drier the tree is, the earlier this process begins. The resin vapor liberated now burns in a flash-like manner and thus triggers a chain reaction. Even adjacent candles can be blown out by the resulting pressure." (Google translate)

    I would try to avoid that heat can accumulate in small areas, e.g. no bulbs near the trunk.

    Edit: A new LED version is definitely cheaper than the smallest fire.
    Last edited: Dec 5, 2016
  9. Dec 6, 2016 #8
    LED is a good idea. An alternative would be to plug the string into a dimmer. You could cut the power to 1/2 or 1/4 and still have a nice glow from those lights. I've put a diode in one lead before. That cuts power in half. Just watch the current rating of course.
  10. Dec 6, 2016 #9


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    You're stringing up the hot ones on the forum --- quickly, men --- to the fire extinguishers.
  11. Dec 6, 2016 #10


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    You're fine, but just use common sense. Don't leave the lights on unattended, or when you go to bed.

    It's a pain when I try to get seasoned wood burning in the stove. I normally use completely dried pine needles as a starter, and even with direct application of a propane torch to the needles they like to smolder before finally lighting up. Obviously, you want to try to keep the lights on the outside away from the needles as much as possible and shut things off if you smell smoke or they start to smolder.
  12. Dec 6, 2016 #11


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    Lol... you mean this?

  13. Dec 7, 2016 #12


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    Yep. Just in case THIS will happen:
  14. Dec 7, 2016 #13


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  15. Dec 7, 2016 #14

    jim mcnamara

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    Hmm. I'm not going to cite fire research. However please consider:
    1. For every percent of moisture content above "dry" (which is assumed to be 16-20% MC) the ignition point of pine needles (leaves) rises 2°C
    2. The ignition point for "dry" leaves is approximately 226°C - less than dry wood because the leaves have lots of volatiles
    3. a C7 with open air circulation can have surface temps of ~175°C

    4. a C7 in a "cute" ornament which prevents air circulation varies - higher. Up to near the dry ignition point.
    1. keep tree watered, get it out of the house after it dries
    2. do not use cute lit translucent ornaments that act as containers

    And you are good - no fires. This does not include wiring problems like arcing, in which case all bets are off.
  16. Dec 12, 2016 #15


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  17. Dec 13, 2016 #16


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  18. Dec 14, 2016 #17
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