Attic cooling and heating hot water.

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Hi,
I am thinking of installing a water tank to recover solar heat in the attic to heat the water.
Can anyone suggest a good (Cheap) air to water heat exchanger that I could use in my attic to recovery the solar heat . One that won't block up easily with tap water minerals, I was thinking of using an auto radiator. ($89.00) Has anyone ever tried to do this?
Any comments would be appreciated.
Thanks
Jay
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PLEASE stop cross-posting this crap all over the world.
all future cross-posters will immediately be killfiled

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Are you daft, or what?
It was crossposted to a small set of newsgroups where it *is* on topic.
It would have been highly *inappropriate* to multipost the same question to each group.
And it is highly inappropriate to complain that someone is using crossposting for its intended purpose.
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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Noon-Air wrote:

No top posting. Tsk, tsk.

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Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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J Poy wrote:

In the attic? Why not put a collector on the roof? This will probably be more efficient, plus it will shade a part of the roof and reduce the heat gain in the attic.
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Paul Hovnanian P.E. wrote:

How about a couple of ordinary domestic heating radiators on the roof, painted black? You should be able to get hold of a couple of old ones very cheaply.
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Well, for one they might have a problem with the pressure. Come to think of it, a car radiator- typically kept below 15 psig by protective cap- would too. Unless either would be used in a closed-loop with a heat-exchanger in the path of the domestic hot water. Which should be rated for the pressure differential- sometimes 80 psig. But then, where to put that exchanger?
With closed-loop, any worry of leached lead from rad would be nil.
Intriguing idea.
HTH, J
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Your idea has merit. Mineral buildup can be a problem in any heat exchanger using hard water, a car radiator would be no worse and is a very efficient exchanger. I suggest using your system as a feed into your regular water heater, it will keep it from having to turn on as often and will back up any shortfall in your heating system. A prefilter will remove silt, which helps, but not dissolved minerals. A water softener will help and will have other benefits but is expensive. When you build it, consider using a bypass with a Y valve, during the winter when the attic air is cold ( I don't know your climate), and during that time you can service it, rinse out mineral deposits with a weak vinegar/water solution. If you are getting a salvage yard radiator, get the biggest one you can for the money. Use a simple fan to boost its efficientcy, wire in a thermocouple to activate it or at least a timer for the hottest part of the day.-Jitney
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I doubt if auto radiators are designed using consideration of maintaining the water to be suitable for human consumption. They may use lead solder, or other materials may be used for corrosion resistance that could be dangerous if consumed.
Bob
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Good point. But newer and refurbushed radiators use lead-free solders. After that, it is copper, brass, and/or aluminum.-Jitney
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J Poy wrote:

Long coiled black hose? Tony
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How hot is your attic. If it is 120 degrees, with a fan blowing hot attic air over the radiator, your water temperature will probably not get over 100 degrees. In the winter, you will get much less.
How much money are you willing ton spend to recover this FREE heat? I think you are spitting into the wind.
Stretch
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"Stretch" wrote:

Come to think of it, I DID convince my older sister to try that once..... :) however....
I recover the heat from my attic & transfer it to the swimming pool. An attic stat can bring on the pool pump & attic fan. cu/al coil. Pool pump also on its own timer for daily minimum run time.
Being the guy you are, and given the same set of circumstances, you'd probably do the same.
Tobby
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It surely will, with a pump controlled by a differential thermostat.
Nick
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I would be concerned about an auto radiator, because you do not know how it has been cleaned, or with what.
Tony has a good idea, and it is often used here in Arizona to heat swimming pools (but the pipe is placed on the roof of the house). More recently, builders have been plumbing houses with plastic in the attic, and it is possible be scaulded in the shower in the late afternoon when the first burst comes out.
A standard solar panel would do well, and one with the glass broken would be cheaper, since all you want is the heat exchanger. It would be hard to get it into the attic, though, since it tends to be 8-feet long. The solar panel controller and pump might help, too.
Kevin
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Sorry about the cross post thought the other newsgroups would be interested in this topic.
Kevin you have a good point regarding the auto radiator. "I would be concerned about an auto radiator, because you do not know how it has been cleaned, or with what."
I asked the dealer he told me the radiator all brand new never used, but I know they defiantly use chemicals for cleaning them even thou there new. I was going to clean it out thoroughly and this will not be for drinking water.
I am trying to keep the overall cost bellow $200.00 as I have many of the parts required already. Only need the piping, heat exchanger and bypass valves. I planned on using a separate preheat water tank in series with main hot water tank. DC closed loop water pump or if possible a way not to have to use one, but I don't think so.
I don't want to use black PVC piping. I like the idea of using the broken solar panel but size limitations and I think it's hard to come by, at a low cost.
My main concern is the clogging with water minerals in the heat exchanger (HE) if I use an auto HE. Might have to add a water filter?
I already thought about heating the swimming pool, but I don't have one. Tobby what type of HE did you use with swimming pool (cu/al) and what the cost was?
Thanks everyone for you comments.
wrote:

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This problem was long ago solved in greece, with heliotherma (=greek, sun + heating) they are boilers you put on the roof and have glass collectors with tubes painted black so that practically you have hot water from the sun 330 days a year.They also have a heating element for the (few) days when the weather is cloudy.
-- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr
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On 2005-07-18 snipped-for-privacy@mindspring.com said: >Newsgroups: >alt.energy.automobile,alt.energy.homepower,alt.engineering. >electrical,alt.home. repair,alt.hvac,sci.energy
>wrote: >>I am thinking of installing a water tank to recover solar heat in >>the attic to heat the water. >>Can anyone suggest a good (Cheap) air to water heat exchanger that >>I could use in my attic to recovery the solar heat . One that >>won't block up easily with tap water minerals, I was thinking of >>using an auto radiator. ($89.00) Has anyone ever tried to do this? >I would be concerned about an auto radiator, because you do not know >how it has been cleaned, or with what. >Tony has a good idea, and it is often used here in Arizona to heat >swimming pools (but the pipe is placed on the roof of the house). >More recently, builders have been plumbing houses with plastic in >the attic, and it is possible be scaulded in the shower in the late >afternoon when the first burst comes out.
>A standard solar panel would do well, and one with the glass broken >would be cheaper, since all you want is the heat exchanger. >Kevin
If you can score one of these, try it outside, without the glass. You may be amazed at how effective it will be. Glass covering is over-rated - couple years ago a physicist reexamined the math on which glass-covered solar panel design was based, found it in error.
Tom Willmon near Mountainair, (mid) New Mexico, USA
Net-Tamer V 1.12.0 - Registered
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That would be very inefficient, unless it has a selective surface.
Nick
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| A standard solar panel would do well, and one with the glass broken | would be cheaper, since all you want is the heat exchanger. It would | be hard to get it into the attic, though, since it tends to be 8-feet | long. The solar panel controller and pump might help, too.
What about simply running the cold water into it the exchanger, then from the exchanger to the normal hot water tank, so that the tank is fed with water that is warmed by the heat source, reducing or maybe even eliminating the need for the tank to do the warming?
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