Author Topic: best solar water pre heater setup  (Read 959 times)

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brkwind2

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best solar water pre heater setup
« on: February 10, 2009, 01:29:04 AM »
I've been preheating water with a couple hundred feet of black garden hose on the inlet to my LP water heater in the summer.  I'd like to have something a little better.  Was looking at the evacuated tube heat exchangers but figured with my hard water they wouldn't last(hand dug well, brick lined).  I don't really have room for a heat exchanger tank where it wouldn't freeze like you might use with a closed loop & glycol & those systems seems relatively expensive.  I was thinking maybe the flat plate collectors like they use for swimming pools might be a good option however they don't seem to be rated for much pressure at high temp.  It looks like that I'll just use what ever I come up with during summer so don't want to invest a lot & I'll have to drain it in the fall.  Do you think the flat plate collector would hold up assuming the water pressure never exceeds say 50 psi?  How suseptible to scaling & lime build up are they?  Any that are easily cleaned?  Maybe I'd be better off building my own collectors but I was worried about logevity & expense.  I'd think wooden frames might not last with the temp extremes.  Anyway, what are your thought?  What are you using if anything.  thanks.
« Last Edit: February 10, 2009, 01:29:04 AM by (unknown) »

GaryGary

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Re: best solar water pre heater setup
« Reply #1 on: February 09, 2009, 06:53:08 PM »
Hi,

This is the system I've been working on:

http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm


Its less than $1000 to build from all new and high quality materials.  

A little scrounging and using the PEX collector version could lower this substantially.

It works in a climate with very cold winters (ours has seen -30F with no problems).


Has performed well so far.  The solar fraction has not gone below 89% even in our worst month, and has been 100% in "easy" months.

http://www.builditsolar.com/Experimental/PEXColDHW/Performance.htm


Your hard water should not be an issue in that the heat storage tank is filled once, and the water is never changed.  If you collect rain water and fill the storage tank with rain water, the collectors will never see mineralized water.  


While its a new design with some new and untried features, I've done a fair bit of testing to try and verify that the chancy areas are OK -- but no guarantees :)


Lots more DIY solar water heater designs from many sources here:

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm


Gary

« Last Edit: February 09, 2009, 06:53:08 PM by GaryGary »