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Hardware Hacking Upgrades Build

Using a House's Concrete Foundation To Cool a PC 465

Posted by timothy
from the thinking-deeper-than-built-in-cable-drops dept.
Agg writes "Well the slab gets poured on Wednesday so I thought I would sink 6 meters of copper pipe in the slab so that I can run my water loop through it when the house is finished. I hope to have water year round at about 16deg [about 61F]. No need for radiators or fans with chilled water coming straight out of the slab!"
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Using a House's Concrete Foundation To Cool a PC

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  • by jawtheshark (198669) * <slashdot @ j awtheshark.com> on Wednesday August 26, 2009 @02:42PM (#29205745) Homepage Journal
    How are you going to explain that if you want to sell that house???
    • by Anonymous Cowar (1608865) on Wednesday August 26, 2009 @02:43PM (#29205767)
      Just saw off the tubes and plug em. It won't hut the resale value of the house very much.
      • Very clever idea. (Score:5, Informative)

        by mollog (841386) on Wednesday August 26, 2009 @03:33PM (#29206673)
        Talk about a heat sink. I'm a little surprised that this sort of technique is not more widely adopted at places like data centers; geothermal or water-source heat exchange, especially for cooling. I have been looking at using a water-source heat pump system to replace my electrical resistance heating/air conditioning system. Big incentives from the government.
      • by athakur999 (44340) on Wednesday August 26, 2009 @03:49PM (#29206915) Journal

        Or sell the house to Ted Stevens and tell him that's where his Internet comes out of.

    • by Shivetya (243324) on Wednesday August 26, 2009 @02:44PM (#29205779) Homepage Journal

      that is what I want to know.

      • by Pyrion (525584) * on Wednesday August 26, 2009 @02:52PM (#29205945) Homepage

        Depends on who you've contracted the work out to. I'm not kidding. Some inspectors "know" the contractors such that they only do a cursory inspection of the finished product before signing it off.

        • Re: (Score:3, Informative)

          by LordKronos (470910)

          Depends on who you've contracted the work out to.

          If you mean who the general contractor is, I think it's him. He said in the forum "I'm doing the house as owner builder".

      • by rolfwind (528248) on Wednesday August 26, 2009 @02:59PM (#29206101)

        Why? It's very similar to what they do when laying radiant heat into the floor (which is very nice btw, over ducted heat, helps with breathing problems).

        Also, like a previous comment suggesting, maybe you should look into radiant heat tubing over copper.

        • by Anachragnome (1008495) on Wednesday August 26, 2009 @03:48PM (#29206899)

          "Also, like a previous comment suggesting, maybe you should look into radiant heat tubing over copper."

          This. I used to live in Alaska and radiant heat slabs were very common. The problem was making sure they never went without heat in the winter. If they did, you ended up with burst pipes and a cracked slab. Big headache.

          The fix is burst-resistant flexible tubing. There is a product called Aqua-pex that fits the bill perfectly. Does not burst when frozen, has a 100-year warranty and is easy to install as it is flexible.

          The other problem with copper in concrete is that the concrete itself is corrosive. It WILL eventually eat through the pipes leading to all sorts of headaches. Usually, when this happens the only fix is drain them and cap the pipes. Most people in Alaska with radiant flooring, even when using Aqua-pex, lay down a second circuit in case there is a problem. They simply hook up the back-up.

          Another suggestion. If you DO use copper tubing, use alcohol, or some other coolant such as glycol, rather then water. You will have better heat transfer as well as less corrosion. This is, of course, assuming you have a closed loop circuit (would be foolish to have anything but).

          • by drinkypoo (153816) <martin.espinoza@gmail.com> on Wednesday August 26, 2009 @04:30PM (#29207573) Homepage Journal

            Okay, I get it, he got the informative for the Aqua-pex. Problem is, Ethlyene glycol decreases water's ability to transfer heat. What it does is raise the boiling point, lower the freezing point, and retard corrosion. Replace your coolant mixture when a voltage measurement between fluid and pipe exceeds one volt.

            We used to use alcohol in radiators, because it does all that stuff and increases thermal conductivity, too. But there were some problems with fires when people used too much. So we just stopped. If you put 100% ethlene glycol coolant in your cooling system it will work, albeit at a very poor efficiency. You might get away with it in the winter.

            If you want something you can just use a little of, there is Red Line Water Wetter, which is often used in racing in all-alloy systems, in which it is sufficient to prevent corrosion. It actually also increases thermal transfer.

            • Re: (Score:3, Informative)

              by kimvette (919543)

              I'll second the Red Line water wetter. It decreased the 90*F+ summer weather operating temperature by >15*F in my ZR-1 (no other changes to the cooling system) so heat transfer is significantly improved. Using it in a geothermal water chiller is a great idea!

          • Re: (Score:3, Informative)

            Coper is the wrong thing for this application. The contact of your rebar to the copper will setup an galvanic corrosion problems. http://en.wikipedia.org/wiki/Galvanic_corrosion [wikipedia.org] Under floor heating systems use PEX like everyone is suggesting. Get some and use it. Get the kind with the aluminum in it. The heat transfer is better. If it's too late to change then you must use something kind of antifreeze in this system. Even with PEX I'd use it because water can still burst PEX and crack your concrete.
            • by Anachragnome (1008495) on Wednesday August 26, 2009 @05:15PM (#29208287)

              Just trying to pass on my own experiences with Alaskan environment and cooling/heating systems.

              I plumbed my ENTIRE house with Aqua-pex (no pesky building codes to deal with). And before I did so, I bought a 20 foot length, filled it with water, capped both ends, and set it outside at -40F. It never burst. Even after a few temp swings of about 50F, there was NO noticeable deformation. I seriously doubt you are going to experience such extreme temps. The other advantage of Aqua-pex is that you do not need any joints IN the slab. Any joints in the circuit simply become another possible location for a leak. Aqua-pex also has a very high shear resistance, so if you are in a earthquake prone area, it provides some protection in that regard.

              As far as coolant, notice I listed ALCOHOL first. Yes, glycol is not a very good conductor of heat, but it is better then burst pipes (if you insist on using copper). The advantage of alcohol is that it will absorb any moisture you fail to remove from the circuit and dilute it, rather then just have that water pool in one location and continue it's corrosion.

              Not sure if anyone else mentioned it, but you need to increase the thickness of the slab (dig deeper dude) wherever you have the circuit as the circuit itself becomes a weak point in the slab. Think perforated paper.

              I do not think it will be an issue here, but the one thing I DO know about Aqua-pex--it cannot withstand long-term UV exposure. It will become brittle if exposed to UV light for any length of time. The solution is to simply wrap it with aluminum tape in any location it is exposed, such as outdoors in sunlight.

            • Re: (Score:3, Insightful)

              by LordKronos (470910)

              The contact of your rebar to the copper will setup an galvanic corrosion problems.

              He's already said in the forum "Im going to separate the copper so that it is not touching the steel reinforcing bar." Of course, that won't protect him from the concrete (as others have pointed out) but the rebar won't be an issue.

      • by MBGMorden (803437) on Wednesday August 26, 2009 @03:09PM (#29206271)

        Unless there's a specific code against it there's no reason why he wouldn't be able to. I work with the Building and Plans department at a county-level government office (I actually admin their software system). When I went through their checklists to add to the new system, it was mostly things you're supposed to do, rather than things you're NOT supposed to do. As long as you do everything on the list you're good to go.

    • by seanadams.com (463190) * on Wednesday August 26, 2009 @02:50PM (#29205891) Homepage

      Who cares, it's a couple pipes sticking out of the slab. Cut 'em off if you're worried about it.

      • by Brigadier (12956) on Wednesday August 26, 2009 @03:31PM (#29206645)

        I care;
        a.) how much copper, btw doesn't concrete corrode copper which is the reason why it isn't placed in the slab anyways.
        b.) for each layer of piping you put down you need an additional 3 inches of slab. proper embedment really requires 3" of coverage else the concrete will crack.
        c.)concrete curing is an exothermic reaction and it takes your typical slab at least a year to completely cure.

        Here is the best part, I'm assuming your in a cold climate with a reasonable frost line (otherwise this would be a stupid idea). If the water in teh pipes stop circulating and freeze it will crack the pipe and the concrete and cause I nice leak. again weakening the concrete overall stress.

        I'm IAAAA ( I am an actual architect) so heed the warning. Or do it properly.

        • by Critical Facilities (850111) * on Wednesday August 26, 2009 @03:51PM (#29206943) Homepage

          btw doesn't concrete corrode copper which is the reason why it isn't placed in the slab anyways.

          Not really. According to this article [copper.org], copper should be fine when embedded in concrete so long as the sulfur content in the concrete additives are minimal.

        • Mod parent down (Score:5, Informative)

          by Overzeetop (214511) on Wednesday August 26, 2009 @04:00PM (#29207073) Journal

          3" cover is most certainly not required. Most commercial floor slabs are 2.5" concrete on 1/2" form deck (9/16 for the pedantic). A 4" slab will have two layers of rebar in it - either as WWR (gauge wire on a 6x6 grid) or as actual rebar up to 1/2" in diameter. That means as little as 1-1/2" of cover over the steel.

          The 3" you may be thinking about is clear cover for steel reinforcement when slabs are cast against earth. In that case, it's to minimize water infiltration and protect the steel from corrosion.

          Freezing of the slab is theoretically possible in a very, very cold environment, but not unless the house is left unheated for an extended time as subzero temps and the typical ground temp is below freezing (an ice lens would have to be able to extend from the exterior of the slab all the way to where the embedded pipes are). In that case the whole house would have to be "winterized" with all lines drained.

          IAASE (structural engineer), BTW.

          • by Brigadier (12956) on Wednesday August 26, 2009 @04:14PM (#29207319)

            damn SE always ruining an Architects fun .... :)

          • Re: (Score:3, Interesting)

            by smellsofbikes (890263)
            I may be wrong about this, since I'm neither an architect nor a structural engineer, but my understanding was that the 3" requirement was for where steel or iron exited the concrete to the outside, as local water infiltration and rust buildup at the concrete/steel/air interface would cause the concrete to crack. Where the steel is contained fully within the concrete the clearance is way less because the assumption is that the steel is in anaerobic conditions. That's just what I learned when I was doing co
        • by Runaway1956 (1322357) on Wednesday August 26, 2009 @04:11PM (#29207269) Homepage Journal

          "( I am an actual architect)" and "requires 3" of coverage else the concrete will crack."

          You may be an architectural student. Rebar and remesh are placed within an inch of the surface to strengthen the exposed surfaces, edges, and corners. This copper tubing can be interlaced with the rebar, with no affect on the strength of the concrete, or increasing the likelihood of cracking.

          You are right though, that for optimal cooling, the tubing should have 3 inches or more of concrete above and below it. Digging a trench for a heavy-up would do the trick.

    • He should, of course, just tell the truth. Dead pan straight. Perhaps with a suitably (but fake) embarrassed laughter.

      In this case it would not hurt at all. A surprised, but friendly buyer. That's it.

      Move on. Nothing here to see.

    • by Cmdr-Absurd (780125) on Wednesday August 26, 2009 @02:54PM (#29205985)

      How are you going to explain that if you want to sell that house???

      Call it radiant floor heating?

    • by mugnyte (203225)

      Older underground oil tanks also have copper tubes poking through the foundation in my neighborhood (houses circa 1905 to 1920s). Flushing, filling and capping old tanks/lines isn't a big deal.

      I'm wondering how useful this would really be, since the concrete would retain any rise in temperatures as well.

      Here's some science
      http://www.concretethinker.com/solutions/Thermal-Mass.aspx [concretethinker.com]

    • by Goaway (82658) on Wednesday August 26, 2009 @03:16PM (#29206397) Homepage

      I don't know about you, but if I buy or make something, it's for me. I'm not there to take care of it for the next owners. If I wanted that, I'd rent.

    • by conureman (748753) on Wednesday August 26, 2009 @03:23PM (#29206517)

      I got a bunch of raised eyebrows when I had two four-gang electrical outlets (one from either leg of the house power) and an exhaust vent fan installed in one of my closets when we built our house. I wanted it for a server farm but couldn't convince anyone that I wasn't going to be farming something else.

      • by fuzzyfuzzyfungus (1223518) on Wednesday August 26, 2009 @03:36PM (#29206705) Journal
        Well, your habit of using the acronym "THC/IP" did rather give the game away....
        • by cromar (1103585) on Wednesday August 26, 2009 @04:56PM (#29208005)
          Now that's a protocol I can endorse! How many grams per second do you typically get when downloading? Is there a flat monthly fee? What are good ISPs* that don't do traffic shaping? Is it easy to encrypt your packets and do you have to pay extra for the aluminum foil/scent resistant wrapper? Can you download across state lines? Or even from Ethiopia?

          *Indica Service Providers
          • Re: (Score:3, Funny)

            Download speeds depend on hardware. Toking ring is somewhat outdated, you were probably all using that back in high school; but still works ok. Ethernet isn't actually that much faster; but the ether has synergistic effects.
  • erm.... (Score:2, Interesting)

    by Anonymous Coward

    Doesn't the house shift and settle? Won't a standard 1 + 1/2 inch copper pipe break during that time?

  • Cool (Score:3, Insightful)

    by flaming error (1041742) on Wednesday August 26, 2009 @02:47PM (#29205837) Journal

    ... literally. But why limit yourself to PC cooling? Turn the slab into a big radiator and pump air from the upstairs/attic through - you can moderate the temperature of your whole house.

  • by seanadams.com (463190) * on Wednesday August 26, 2009 @02:47PM (#29205839) Homepage

    The steel rebar and the copper pipe being in close proximity will make them act as electrodes on a battery. This will cause the steel anode to slowly be destroyed by the chemical reaction.

    Is it a practical concern in your case? I doubt it, but if they haven't poured yet, it wouldn't hurt to wrap the copper pipe in some PVC tape. This will reduce the thermal coefficient though. Maybe just do it where it passes within a couple inches of the rebar.

  • I do hope there is a full write up posted after a few months or a year, to see how well this works.
  • by eldavojohn (898314) * <[moc.liamg] [ta] [nhojovadle]> on Wednesday August 26, 2009 @02:50PM (#29205911) Journal
    If you were pouring the concrete, why didn't you put it outside of the concrete [japru.com]? You would probably incur less structural risk ... although I doubt a pipe that small would have much effect. More and more people are building new houses with geothermal exchange [geocomfort.com] to help mitigate costs in heating and cooling.
    • Re: (Score:3, Insightful)

      by Smoke2Joints (915787)

      not only that, but i would have thought that driving the copper pipes into the water table would do much more for cooling than surrounding it in concrete.

      • Re: (Score:3, Informative)

        by hardburn (141468)

        Not necessarily, just need to get below the frost line. Even in climates where the temperature can swing between 0 and 90F throughout the year, the temperature under the frost layer doesn't change much more than 10F. That's how vertical geothermal loops work.

        The submitter's idea is similar to a horizontal loop, which for houses, is a cheaper option than vertical loops (since you don't have to dig as far down), but you need a very large backyard to do it (a few acres, IIRC).

        IMHO, the submitter's best bet wou

      • Re: (Score:3, Informative)

        by julesh (229690)

        not only that, but i would have thought that driving the copper pipes into the water table would do much more for cooling than surrounding it in concrete.

        If you're Doing It Right(tm) you don't want to be building anywhere even remotely close to the water table. Unless you're on a very poor site, the water table should be at least half a metre below your foundations, preferably much more. You want to dig down that far just for a bit of CPU cooling?

        (Now, if you were running a ground source heat pump [wikipedia.org], that m

    • by CopaceticOpus (965603) on Wednesday August 26, 2009 @03:22PM (#29206505)

      That first link is so bizarre, sitting within a post which otherwise seems very logical. My brain is short circuiting as it tries to find the connection between underground piping and spinach pizza.

  • Don't Use Copper (Score:5, Informative)

    by Anonymous Coward on Wednesday August 26, 2009 @02:50PM (#29205915)

    Use PEX instead. Copper will eventually fail. Look at the material that is used for radiant flooring.

  • by Anonymous Coward on Wednesday August 26, 2009 @02:51PM (#29205925)

    Without proper thermal throttling, your roof could come off, even with a passive heatsink.

    I think Antec makes a two-story-high fan that might work perfectly in such a situation, but the neighbors might be bothered by the LEDs.

  • by jayhawk88 (160512) <jayhawk88@gmail.com> on Wednesday August 26, 2009 @02:51PM (#29205927)

    In most areas of the country, it's not a question of if but when your house settles and puts some nice big cracks in your concrete. Whether or not it would be a enough to damage the pipe is another question, but if you're relying on it to cool a semi-expensive piece of hardware, I might be a little nervous about it.

    Also, seems like this will severely limit your options for where to put your computer physically.

    Are fans really that horrible? They make them fairly quiet now. Is that extra .4 Ghz really worth all that kind of effort?

  • by cowscows (103644) on Wednesday August 26, 2009 @02:56PM (#29206029) Journal

    Ground Source heating/cooling is a pretty nifty technology, and can be applied to a whole house HVAC system, rather than just a computer. It obviously requires more tubing than a single computer would, and in most climate will still require some supplemental heating/cooling for more extreme temperature days, but it's still awesome. It does have some upfront costs though.

    This idea to do it for a particular computer is a clever idea. I personally wouldn't want the pipe to actually be moving horizontally through my slab, I'd rather dig as small a diameter hole as is possible, but deeper under the slab, and just have the line penetrate the slab vertically. The deeper you go, the more stable the temperature becomes, and the less hollow copper pipe you've got running through the slab, the less you weaken it.

  • by OzPeter (195038) on Wednesday August 26, 2009 @02:58PM (#29206091)
    And you haven't thought through the consequences yet? That my friend is a project that has failure written all over it.
  • by name_already_taken (540581) on Wednesday August 26, 2009 @03:07PM (#29206253)

    Getting rid of heat by dumping it into the ground is a great idea.

    The problem is, you're dumping heat into your house's slab, not the ground. You need to put the pipes several feet underground.

    All this is is a mild underfloor heating system. If that's what you're trying to achieve, ok, but if you're also paying for air conditioning to remove heat from the house, this is probably not worth it.

  • by Anonymous Coward on Wednesday August 26, 2009 @03:17PM (#29206413)

    I live in the midwest, and did the same thing 4 years ago, when I had my house built... I use a heat-pipe to fluid thermal exchanger on my ESXi server as well as my gaming rig.

    It will in no way harm your resale value, and if your inspector has a brain, it has no impact on the inspection...

    Due to expansion and contraction concerns, I had that small (8`x8`) portion of the concrete isolated....

  • See "Levittown" (Score:3, Informative)

    by J4 (449) on Wednesday August 26, 2009 @04:28PM (#29207541) Homepage

    Copper pipe in cement + time = leaks

    In the 50's when they were cranking out cheap housing, slab houses with copper piped radiant heat in the floor
    was the spec. They all started leaking from electrolytic corrosion and had to be retrofitted with baseboard.
    Side note: Also made conditions really sweet for termites.

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