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Odd question about cast iron

Post in 'DIY and General non-hearth advice' started by Eric Johnson, Jan 17, 2008.

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  1. Eric Johnson

    Eric Johnson Mod Emeritus

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    If you poured 200-degree hot water into a cast iron pot or other container that was at, say, 20 degrees, would it crack?

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  2. mikeyny

    mikeyny Feeling the Heat

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    I am not sure but I think if the cast iron is real hot and the water is cold something bad would happen. Kind of like the old time steam locomotives taking on water with a hot empty tank. Kaboom. My great grandfather was killed on x-mass eve around the turn of the century when I steam locomotive exploded. Pretty messy.
  3. babalu87

    babalu87 New Member

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    I cherish my cast iron pans too much to find out.

    You can buy a small pan for less than $20 at Wal-Mart............ be sure to wear safety goggles......... AND A CUP!
  4. jqgs214

    jqgs214 Minister of Fire

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    UMM why do you ask?
  5. Cazimere

    Cazimere Member

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    NO, it would not crack. Water only cracks when frozen.
    Would have thought a weatherman would have known that.
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    Mike: My condolences. Hot cast iron and cold water makes steam which certainly has explosive potential. I don't think the reverse is true.

    babs: Thanks for the safety tip.

    Wxman: It's kind of personal, so I'd rather not say.

    Caz: Wisecracker!
  7. TMonter

    TMonter Minister of Fire

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    I don't think so Eric, the energy transfer rate imparted from the hot water to the cast iron just wouldn't be fast enough to cause the metal to expand too rapidly for cracks to form. Maybe under repeated cycling you might have an issue.
  8. Eric Johnson

    Eric Johnson Mod Emeritus

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    Thanks. That's about what I thought.

    What I'm doing is a bit confusing, but I'm using a couple of cast iron radiators in unheated space as a potential gravity-feed heat dump for my boiler in case the power goes out or I otherwise have to cool it off without the benefit of a pump. They're in the attic above the boiler room in my barn. Normally these rads would be full of water and when you opened the valves, the hot water from the boiler would circulate through the radiators and dissipate the heat. But since I don't have antifreeze in my system, the radiators are empty. I figure if the time comes, I can open the valves and the bleeders and fill them with hot boiler water and let them do their thing, then drain them later when the power is restored. I just don't want them to blow up if it happens to be really cold.

    An alternative would be to fill them with plain water and just crack the valve enough to keep them from freezing. But I'm afraid my more frugal side will take over and I'll miscalculate and freeze them up on a cold night.

    It's pretty primative, I know, TMonter, but it's the situation I'm in.
  9. guy01

    guy01 Member

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    Hey cool ,I have some cast iron pans in the basement I don't care too much fore I'll let you know
    Guy
  10. guy01

    guy01 Member

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    OK today is the day it's 10° out
    Guy
  11. guy01

    guy01 Member

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    That was boring nothing interesting at all happened wanna try a 400° pan and really cold water?
    Guy
  12. saichele

    saichele Minister of Fire

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    Now that you explain it, I'm reminded of the old single pipe boiler heat systems - steam goes up to a cold rad, condenses, and the water drains back down the same pipe. Dunno about 20F, but I bet there were a lot of times the steam hit a 40F rad. Certainly once in a while wouldn't kill it, maybe cut loose some of the rust and crud inside...

    Steve
  13. zzr7ky

    zzr7ky Minister of Fire

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    Eric -

    No you shouldn't have a problem. Water just doesn't have enough thermal energy at low pressure. A pound of steam carries 60 times the energy IIRC. I'm even more confident since you aren't cycling these things many times per day.

    I have seen a setup like you describe. In a geothermal system in rural AK the homeowner used a series of the "along the wall" radiators from a commercial building salvage job to put down the temp to feed a series of concrete cistern/hot tubs. It worked very well. However the homeowners worst fear was an interuption in his feed water which could cause lots of freeze damage. It worked well enough that his steal and plastic sheet 'tub house' was comfy in well below zero temps.

    The hot water flush on the toilet took some getting used to!

    ATB,
    Mike P
  14. guy01

    guy01 Member

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    I must be missing something but if they are above your boiler and you can't pump how do you get the hot water to the cold place
    Guy
  15. guy01

    guy01 Member

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    Never mind i'll call it a brain fade
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