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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 Anonymous Cowar (1608865) on Wednesday August 26, 2009 @01:43PM (#29205767)
    Just saw off the tubes and plug em. It won't hut the resale value of the house very much.
  • It will work fine. (Score:1, Informative)

    by Anonymous Coward on Wednesday August 26, 2009 @01:44PM (#29205775)

    Just don't plan on being able to move your desk.

    Copper would be a waste of money tho. Use one of the many types of plastic hose already made for this application.

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

    by Anonymous Coward on Wednesday August 26, 2009 @01:50PM (#29205915)

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

  • by jayhawk88 (160512) <jayhawk88@gmail.com> on Wednesday August 26, 2009 @01:51PM (#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?

  • Re:Ice cooler! (Score:5, Informative)

    by Moryath (553296) on Wednesday August 26, 2009 @01:51PM (#29205933)

    6 ft down doesn't actually provide much cooling. If you want a "neutral" temp, you need to go well underneath the slab.

    Plus, you're "sinking" to a temp of 40-50F, and you have to consider that the concrete itself is a fair insulator, so you won't actually lose as much heat as you hope.

  • by cowscows (103644) on Wednesday August 26, 2009 @01:56PM (#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 Maddog Batty (112434) on Wednesday August 26, 2009 @02:02PM (#29206175) Homepage

    Apart from the fact that concrete attacks copper. All copper water pipes placed in concrete have to coated in plastic to protect them (at least in the uk).

    I would use underfloor heating plastic pipes which are designed for this job. Sure they would need to be longer to get the heat transfer but the price would be similar and would be far less likely to leak. They certainly work fine in getting 6kW of heat into my house so absorbing a few hundred Watts would not be a problem.

  • Re:Ice cooler! (Score:3, Informative)

    by Brian Gordon (987471) on Wednesday August 26, 2009 @02:04PM (#29206209)

    Six meters.

  • by name_already_taken (540581) on Wednesday August 26, 2009 @02:05PM (#29206215)

    Houses have been built with copper pipes and steel rebar and rewire in the slab for decades now without any electrolytic effects showing up.

    Once the concrete is cured, it is no longer an electrolyte. Concrete is not a great electrical insulator, but it's not a great conductor either.

  • by name_already_taken (540581) on Wednesday August 26, 2009 @02:07PM (#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 MBGMorden (803437) on Wednesday August 26, 2009 @02:09PM (#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 R2.0 (532027) on Wednesday August 26, 2009 @02:11PM (#29206317)

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

    Negative.

    http://www.copper.org/applications/plumbing/techcorner/problem_embedding_copper_concrete.html [copper.org]

    They use PEX because it is cheaper and easier to install, NOT because of its longevity.

  • by djh101010 (656795) on Wednesday August 26, 2009 @02:22PM (#29206493) Homepage Journal
    PEX tubing is used for this application, at least in the US. Copper may be a better conductor, but, it's a LOT more expensive. If you can have double the length, still get the heat density you need, at less cost of copper spaced further apart, why not use it? The fact that it IS what is used, and the whole corrosion problem with copper and concrete, are probably why it's done the way it is. Not all plastics have the same thermal insulative properties.
  • by hardburn (141468) <hardburn@@@wumpus-cave...net> on Wednesday August 26, 2009 @02:22PM (#29206501)

    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 would be to use these pipes for underfloor heating. Since the house is still being built and he doesn't appear to mind having his computer stuck in a certain location, he can put some pipes going outside to a small AC unit. It'd work much like central AC, except connected only to the computer. Sub-freezing temperatures are possible, which he's not going to get with this setup, since the fluid can't get any cooler than the concrete slab foundation. The AC setup can be made by salvaging a window sill AC unit, or built yourself with an AC compressor and heat exchanger from a car.

  • Very clever idea. (Score:5, Informative)

    by mollog (841386) on Wednesday August 26, 2009 @02:33PM (#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.
  • Re:Ice cooler! (Score:5, Informative)

    by SatanicPuppy (611928) * <[Satanicpuppy] [at] [gmail.com]> on Wednesday August 26, 2009 @02:43PM (#29206819) Journal

    This is exactly what I came in here to say. Your concrete isn't some magical source of coolness: it obeys the laws of thermodynamics just like everything else. And a mere 6 meters of pipe means that that warm water is going to circulate frequently, warming up the concrete and making your computer overheat.

    Putting the pipe in the slab won't have any effect on the slab or the resale of the house, but it probably won't have any effect on your computer either.

    If you want to try some kind of fan-free passive cooling, you'd be better off putting in a swimming pool, and running some radiant pipe in the deep end...Fractionally heat your pool, and significantly cool your computer (unless you live in a really hot area).

  • by Anachragnome (1008495) on Wednesday August 26, 2009 @02:48PM (#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 Critical Facilities (850111) * on Wednesday August 26, 2009 @02:51PM (#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 @03:00PM (#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 Runaway1956 (1322357) on Wednesday August 26, 2009 @03:11PM (#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.

  • Re:Very clever idea. (Score:3, Informative)

    by afidel (530433) on Wednesday August 26, 2009 @03:12PM (#29207275)
    I think you mean more like 3,000W/m^2 and even that is kind of low for a modern datacenter. A rack is only ~.65m^2 so even with aisle space being equal to rack space that's only 4kW per rack.
  • by 2gravey (959785) on Wednesday August 26, 2009 @03:15PM (#29207347)

    c.)concrete curing is an exothermic reaction and it takes your typical slab at least a year to completely cure.

    The small amount of heat he is pumping in won't hurt that and will make the reaction slightly faster.

    You missed his point. "Exothermic reaction" means the concrete will be emitting heat and therefore will not make a good pc cooler until the curing is complete.

  • by Anonymous Coward on Wednesday August 26, 2009 @03:18PM (#29207393)

    you will not get a better heat transfer fluid than water. Don't be stupid. adding glycol to the loop will depress the freezing point and eliminate pipe bursts in the event of long term heat outage. You can add anti corrosion chemicals at 1mL/L_H2O to prevent corrison, no need to destroy the heat transfer properties of the water.

  • Re:Ice cooler! (Score:3, Informative)

    by Moryath (553296) on Wednesday August 26, 2009 @03:19PM (#29207411)

    The "large area of cement" isn't going to work nearly as well as you think. Your "basement concrete floor" temperature is still within 10 or so degrees of your ambient air temperature.

    Now, assuming he lives in Moosefuck, Alaska or something, perhaps the ground underneath his house is significantly cool enough to provide some help. Given the flora in the area, I rather doubt that. Further, the fact that he's building a slab, rather than a proper basement foundation, indicates that he's somewhere in the Southern/Southeastern US, in a low-lying area where building a basement foundation means digging down below the water line.

    The net effect, going by thermodynamics, of his given rig is going to be roughly the same as if he'd bolted his circuit of copper to the wall by his bed and just let it vent heat into the ambient, air-conditioned house.

  • by Runaway1956 (1322357) on Wednesday August 26, 2009 @03:20PM (#29207431) Homepage Journal

    http://www.copper.org/resources/properties/protection/underground.html [copper.org]

    That site says that concrete does not corrode copper. My experience seems to back that up. (Yes, I've built and I've demolished buildings.)

    One problem that might cause corrosion, is allowing anything to be electrically grounded through the copper. Read the link. Using a double insulated pump would be a good idea, but not necessary.

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

    by J4 (449) on Wednesday August 26, 2009 @03:28PM (#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.

  • by drinkypoo (153816) <martin.espinoza@gmail.com> on Wednesday August 26, 2009 @03:30PM (#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.

  • by zerosomething (1353609) on Wednesday August 26, 2009 @03:32PM (#29207609) Homepage
    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 Anonymous Coward on Wednesday August 26, 2009 @03:49PM (#29207903)

    Well if you read the text at copper.org (an unbiased source?) it really sounds more like it is "technically" possible, but there are a lot of common factors that can ruin the install. Heard that MA will not allow you to put copper pipe in slabs for radiant heat (thousands of failed copper installs in slabs in MA provide an ample counter examples). Pex tolerates thermal expansion better, can even handle cracks since it flexes and can handle cinder and fly ash. In short it is better

    "The copper tube must be completely embedded in the concrete and adequate provision for thermal expansion should be provided where the tube enters/exits the concrete."

    "provided that allowance is made for the lateral thermal expansion and movement of the tube and protection of the tube from abrasion. This can be done by insulating the tube where it passes through the wall or by wrapping the tube with an approved tape (to avoid abrasion) and installing it through a sleeve. Please refer to your local plumbing code for specific requirements regarding the protection of pipes and tubes passing through concrete and masonry floors and walls."

    "According to the Portland Cement Association the interaction of copper with both dry and wet concrete should not cause a corrosion concern. However, copper should be protected when it comes in contact with concrete mixtures that contain components high in sulfur, such as cinders and fly-ash, which can create an acid that is highly corrosive to most metals including copper."

  • Re:Explanations (Score:3, Informative)

    by seanadams.com (463190) * on Wednesday August 26, 2009 @04:11PM (#29208225) Homepage

    When you say 'either leg of the house power', you don't mean different power phases, do you? You can have great fun with co-connected kit (eg a printer and a server) when they are on separate power phases - sparks can fly!

    That's absolute nonsense. It is done all the time, especially in data centers where a pair of outlets on opposing phases is wired with a common neutral. It gives you double the power for just one more conductor. Or for 3-phase, triple the power for two more conductors. It is explicity allowed by NEC (210.4, "mulitiwire circuits") and is perfectly sound wiring practice. Even a UPS will have its own outlets on opposing phases, because it makes for a much more efficient design internally.

  • by Anachragnome (1008495) on Wednesday August 26, 2009 @04:15PM (#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.

  • Lets expand on that. (Score:4, Informative)

    by djdavetrouble (442175) on Wednesday August 26, 2009 @04:39PM (#29208655) Homepage

    Why is it that we haven't built datacenters in places with natural cooling. gives a new meaning to the phrase, sent to siberia.
    I know I am not the only one [datacenterknowledge.com] with [nasa.gov] this [halfbakery.com] obvious [datacenterknowledge.com] Idea. [itpro.co.uk]

  • by Anonymous Coward on Wednesday August 26, 2009 @04:49PM (#29208793)

    This reply is in support of prior posts, and is only meant to be of an informative nature.

    I love hearing about water additives.
    Especially when in regards to cooling computer equipment. One commonly sees ethylene-glycol/water mixtures in watercooled rigs. I can't help but wince and then shake my head in disappointment whenever I see the neon green flowing through their Tygon or Primoflex.

    Provided as a quick reference: http://www.engineeringtoolbox.com/thermal-conductivity-liquids-d_1260.html

    PC's are not automobiles, and the cooling systems for each have very different requirements. Unfortunately, many PC enthusiasts fail to take this into account. Glycol mixtures will always decrease thermal conductivity within a PC's watercooling system. Additionally, the added viscosity tends to inhibit flow, and wear down centrifugal pump parts prematurely - in much the same manner that submersion systems chew through cooling fans.
    In short, using a glycol-based solution within a PC environment is not desirable - ever.

    Veterans of the PC watercooling game who have done their research will concur that the best anti-surfactant, anti-fungal agent to use within a PC's watercooling system is Red Line's Water Wetter.

    Lastly, plenty of very good reference material on the subject of water cooling (and much, much more) can be found at http://electronics-cooling.com/

  • Re:Very clever idea. (Score:3, Informative)

    by nschubach (922175) on Wednesday August 26, 2009 @04:50PM (#29208823) Journal

    Oh and we have nuclear power here, so electricity is cheap compared to surrounding states.

    My parents live in the distribution network of a nuclear plant and it actually costs them more because the plant has to pay all the schools and public facilities in the area a "hazard" tax just to exist. The up side to that is that the schools in the area have quite possibly the best facilities I've ever seen. It's really too bad it was re-distributed wealth and my parents are paying for a school that we didn't get to attend.

  • by julesh (229690) on Wednesday August 26, 2009 @05:23PM (#29209305)

    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 might be different...)

  • Re:Very clever idea. (Score:3, Informative)

    by LoRdTAW (99712) on Wednesday August 26, 2009 @06:12PM (#29209989)

    It might be that they county/state does not allow the aquifer table to be used for such a purpose. You don't want water from a data center contaminating the ground water supply that is also used for drinking. Even a heat exchanger could leak causing contamination. The law might also state that the aquifer table cannot be used for industrial/commercial processes or require costly annual permits.

    If the data center is located near other buildings, a system of pipes could be used to bring heated water to nearby buildings for heating. Or if the data center is housed in a larger building with other occupants the waste heat could be used to heat the the entire building, the tenants could be billed by the data center to recoup energy costs. Plenty of ways to use the heat but often the initial installation costs make it cheaper to just dissipate the heat into the atmosphere.

  • by LordKronos (470910) on Wednesday August 26, 2009 @06:30PM (#29210163) Homepage

    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".

  • Re:Very clever idea. (Score:4, Informative)

    by hairyfeet (841228) <bassbeast1968 AT gmail DOT com> on Wednesday August 26, 2009 @07:51PM (#29210863) Journal

    I was talking about putting one or two large fans in the bottom of the silo there Chuck. You see those silos would be like a giant heat pipe. you could put several levels of rack there, and with proper spacing one or two fans at the bottom blowing up could cool the entire setup by sucking cool air from the bottom and using this to blow nice cool air all the way to the top, where the warmer air would be expelled. You DO know that heat rises and cool falls, yes?

    And nobody was talking about leaving the bloody top open. They actually have vents placed at the tops of those things in case a fuel leak required quick venting. Simply use the already existing infrastructure to blow the hot air out year round. Believe me the military already thought of things such as rain, or do you believe they wouldn't vent if it was a rainy day? Those things actually have quite nice ventilation systems in place already. Adding a couple of large fans at the bottom to circulate all the cool air at the bottom of the shaft would be a very minimal expense compared to the amount of cooling you would get from pulling air from that far underground and using that shaft for extra cooling.

  • by kimvette (919543) on Wednesday August 26, 2009 @07:52PM (#29210877) Homepage Journal

    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:Very clever idea. (Score:3, Informative)

    by fractoid (1076465) on Wednesday August 26, 2009 @09:28PM (#29211543) Homepage

    I wonder why they didn't just drill down?

    Two potential reasons: First, many land titles only actually give you the rights to the surface, down to a depth of a few feet/meters. Secondly, the ground conducts heat fairly poorly (that's why it's a constant temperature a few meters underground regardless of the surface temperature) and so once you've heated up that rock and soil you've drilled into, it's going to stay hot for a long time.

  • Re:Very clever idea. (Score:3, Informative)

    by barzok (26681) on Wednesday August 26, 2009 @09:49PM (#29211681)

    Only to a point. Then you have to worry about the snow melting, then immediately freezing (ambient temperature too low), turning that parking lot into an ice rink.

    And in the summer, instead of that parking lot being a heatsink, it'll be a giant heat sponge, and it'll heat your equipment, instead of cooling it.

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