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Thread: solar water heater

  1. #1

    Question solar water heater

    I'm building my own solar water heater I need some technical advise.
    1. I will be using roof top solar panels and will need to convey the heat to the basement for storage. Is there a more cost effective 1/2" material than copper that will withstand the temperatures (200 degrees or more)
    2. What is the best insulation for the pipes
    3. The design includes a heat exchanger that will involve a concrete slab with the hot water running through ir. I I use copper, will it hold up and not corrode in the concrete? I need it to withstand the temperatures and transfer heat easily. Will Pex work?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Concrete and copper aren't all that great together. Pex can't handle that high of a temp, at least at higher pressures...it might work since your pressure would likely be fairly low. It gets derated as the temp goes up for the amount of pressure it can handle.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Here's a good site, might be some answers?
    http://builditsolar.com/

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    Master Plumber master plumber mark's Avatar
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    Talking need more informatoin

    Their are a lot of different systems out there...

    It really depends on which type you are installing...

    Will the panels have water or antifreeze or oil going through them???

    The oil type are the best...from what I remember...Like the NOVAN style from the early 80s..

    Wirsbo pex for radiant heating under the concrete floor
    would be good..

    probably best to reveal more information or links to what you are considering doing...

    these systems are a little complicated and can be a pain if you are not capable of tinkering with them yourself...

    and some are much better than others..



    post a link to what you are looking to install...

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    Master Plumber nhmaster's Avatar
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    What is the highest anticipated temperature at the slab inlet?

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    Computer Programmer Bill Arden's Avatar
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    One thing people forget is that the higher the water temperature, the lower amount of heat you get since the system radiates heat back out of the panel.

    This means that it is best to increase the pump speed so that the water temperature is more even and as low as possible.

    FYI: The light concentrating unit we are designing reached 400F with an outdoor temp of -10F during a "dry" test a few weeks ago. However this still means that we have to run the water at a much lower temperature to capture as much heat as possible.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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    Plumber Cass's Avatar
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    A 250' roll of K copper, unrolled on a sun exposed roof, painted flat black, with an adjustable speed recirculating pump, will work well in a non freezing area.

    You might be able to hook it into your still and pre heat the mash also...

  8. #8
    Extreme DIY Homeowner Scuba_Dave's Avatar
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    Whats a 250' roll go for these days? Copper prices seem to be down at least for electric wire

    I'd like to build a heater for warmer weather use
    But it would be connected before the electric water heater - as a pre-heater. If it gets too hot wouldn't that cause a pressure problem in the tank?
    A different recirc system in the same structure (with glass panels) would be used to heat the pool. So I would have a means of keeping the temperature down
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default solar

    The solar pump or circulation is controlled by the water heater, AND the temperature diffential between the coil and the tank. If the tanks temperature setting is satisfied the water in the coil will be heated to whatever temperature the sun can heat it too, so you cannot depend on it ALWAYS being below the safe level for PEX or anything else other than copper. If you just put a coil of black copper on the roof, you have absolutely no control over what the temperature in the tank will be. AND it is very common for even a controlled solar system to trip the reset hi-limit on the upper thermostat. Black finned copper is the only material that will give a rapid response to changes in the solar radiation.

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    Extreme DIY Homeowner Scuba_Dave's Avatar
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    The water coming out of my pool solar hot water heater tops 130 when it is 1st turned on. It quickly drops to about 95
    On camping trips we took solar hot water bags, quite often they were too hot
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

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    Master Plumber nhmaster's Avatar
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    My dad always heated the pool with a 500' roll of black plastic well pipe thrown on the ground and piped through the filter. Worked great. Looked like crap for a few weeks.

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    Master Plumber nhmaster's Avatar
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    Almost forgot

    www.calleffi.com

    Download Idronics3 I believe (might be idronics2) Great solar read.

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    Master Plumber master plumber mark's Avatar
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    Talking here is something that would work great




    I think a tree was cut down or chopped back to make this high tech deivce work properly

    Cass, I think this picture is from somewhere over in Kentucky

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