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Using a House's Concrete Foundation To Cool a PC
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!"
How are you going to explain that if you want to sell that house???
Ahhh...the great dumpster continuum. Many a free computer will be found there. -- sowth (748135)
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.
If you were pouring the concrete, why didn't you put it outside of the concrete? 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 to help mitigate costs in heating and cooling.
My work here is dung.
Use PEX instead. Copper will eventually fail. Look at the material that is used for radiant flooring.
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.
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.
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.
One time I threw a brick at a duck.
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.
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.
wot no sig
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.
Putting moderation advice in your
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.
Putting moderation advice in your
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.
"People who think they know everything are very annoying to those of us who do."-Mark Twain
Negative.
http://www.copper.org/applications/plumbing/techcorner/problem_embedding_copper_concrete.html
They use PEX because it is cheaper and easier to install, NOT because of its longevity.
"As God is my witness, I thought turkeys could fly." A. Carlson
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.
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.
The cost of that cleanup, of course, will be borne by taxpayers, not industry.
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.
Best regards.
Yeah, that 6m of copper tubing will probably make the house explode, right?
Learn about Photography Basics.
Well, your habit of using the acronym "THC/IP" did rather give the game away....
I rented a house in Kentucky that had this problem. The house was built with copper pipes embedded in the foundation for water, but to save money apparently the builder had just put bare copper pipe instead of putting it in plastic conduit. About 5 years after the house was built, the pipes started failing (in my case, it was a pipe that led to an outside faucet I never used, and I only discovered it when my water bill went from its normal $20 to about $280 one month).
Fortunately, the landlord in my case was the builder, so he sent a team out to reroute all the pipes up through the ceiling (which was a major mess, but the workers were really careful with my stuff and used sheet plastic generously to contain all the drywall dust, etc) and refunded my water bill for the month. He also replaced all the carpet in the house, since the workers pretty much ruined the carpeting running the new water pipes. So after a week or so of hassle, I had a freshly-painted house with brand new carpeting.
Apparently (as it was explained to me by the landlord) bare copper *can* sometimes work in concrete, but it depends on the acidity of the concrete, which probably depends on the stone and filler used. The landlord admitted he messed up and didn't measure the acidity of the concrete (and he had built and sold a lot of houses in my neighborhood, so he was looking forward to a LOT of repairs like this).
In any case, lining the copper with something is probably a good idea, even if it does reduce heat exchange. Or just use radiant heat pipe as the parent suggests.
After all, there's the heat generated by a computer (maybe 150 watts) to deal with, and 6 meters of pipe. With that much pipe, just the copper exposed to air would probably dissipate enough heat without needing forced air, so exchanging the heat through plastic into a concrete biomass should work just fine.
"This post contains words, known to the State of California to cause thought. Wash brain thoroughly after reading."
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).
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
"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).
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.
Is it just my observation, or are there way too many stupid people in the world?
http://www.copper.org/resources/properties/protection/underground.html
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.
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You've obviously never been lied to about birth control then.
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.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
While we all appreciate the thoughtful and incisive commentary on the appropriate symbol for "feet", I must humbly point out you misspelled "apostrophe", which has the unfortunate effect of putting your credibility as a master of punctuation in some... doubt.
But yes, since Slashcode fails to recognize ANY of the HTML4 entities for "prime" , we will have no choice but to fall back on that ancient artifact of the bygone typewriter era: the apostrophe key. I blame GP commentor's lamentable faux pas in choosing the wrong key on a lack of training in typewriter keyboarding. This modern computer keyboarding is an anarchic madhouse of unregulated freedom and undisciplined overabundance of choices. It's good to have the leadership and mentorship of those who know better, in order to provide guidance to youngling slashdotters. Thank you, evilbessie.
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