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Thread: Off the grid water heating and radiant floor...tubes?

  1. #1
    DIY Junior Member David95966's Avatar
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    Default Off the grid water heating and radiant floor...tubes?

    I'm moving off he grid. I wanted to get tubes and radiant floors. My wife wants DIY. She says the tubes leak, break and are a lot of work.

    Considering the tax breaks, what the best bang for your buck system? Are brands important? Is there an online reseller that explains what to buy and how to install it!? Should I truss the local installers to know anything or recommend the right product? Do I have to understand tis much better than I do to pick the right system? Has this technology improved in the last five years? What do people who own these systems think?
    Last edited by David95966; 11-05-2013 at 09:05 PM.

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    DIY Senior Member Reach4's Avatar
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    What does "off the grid" mean to you? What would be powering your tubes, radiant floors, and pumps?

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    DIY Junior Member David95966's Avatar
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    The sun would be powering the tubes. PV solar would power the pumps. Hot water from the tubes would heat the floors.

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    Master Plumber master plumber mark's Avatar
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    Default being totally off the grid is a lofty goal...

    Your wife is probably right about this ....
    under floor heating with only solar is a good idea
    but you better have a back up system on line and ready
    to heat, on those cloudy days....

    have you considered the amount of trouble you
    are getting yourself into with a totally solar system??

    there are a hundred different ways to go solar and I prefer
    the more passive ways that dont require a degree in enjeneering
    or being required to do a "space walk" in a blizzard to make repairs....

    from reading your post, you dont sound like you know much about what you are getting yourself into..... Tax breaks have mostly gone away, and these things are not for the beginners.....

    If you have to ask someone to install it for you, or you think you are gonna get advice from tech support. how to do it, or what to do when it breaks down... you are gonna be totally dependent on the guys tha tinstalled it for you....

    so you are not off the grid like you think you are, but just paying someone else to maintain the system

    Question..do you know the difference between passive and active solar systems???





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  5. #5
    In the trades Dana's Avatar
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    Default

    Mark has it right. The best bang per the buck is the air sealing & insulation, windows, and the analysis to make it a truly passive self-heating design, with very low peak & average heating loads. The only good off-grid home is the one that uses electricity only for essentials, not big energy uses like space heating.

    With all of the extra PV and batteries required to run the pumps. The lifecycle per-kwh cost of the batteries alone is on the order of 50 cents/kwh, and the more you need power to make stuff work the more battery, inverter & PV you need.

    If optimize the insulation, passive gain, and thermal mass of the house to where your heat loads are under 20,000BTU/hr even on the darkest coldest nights you can heat with a small EPA-rate woodstove that NEEDS no PV, pumps or batteries, and you can size your PV to run the essentials (like a small refrigerators and some lights, and maybe your notebook computer with the internet link, etc.) And you can size the solar thermal for your hot water needs.

    There has been no recent performance breakthroughs on solar thermal. In most instance flat panels are the better bang/buck- evacuated tubes make sense when you have a very high delta-T between the working fluid and the outdoor ambient. If you're moving to 10,000' in the Sierra it may be worth it to gain some mid-winter performance, but in Oroville you'll get more performance per dollar out of flat panels.

    There have been major price/performance improvements on PV in the last 5 years, but alas, not so much for the storage batteries & inverters, which will be more than half the upfront cost of the system. Buck-a-watt panels abound, but at the very low end price fringe not all vendors stand up, using sub-standard LCA and flimsy mechanical components. But it's a moving target- volume pricing on first-quality PV will hit 50 cents/watt in under 5 years, as better kerfless thin-silicon mono & poly crystaline panels hits full production stride. But the price of lead-acid batteries and charge controllers/inverters aren't on a similar falling price trajectory.

    Grid tied inverters are coming down in price though, and sub-$2/watt all-in pricing (installed) isn't far away. (It's already there in Germany, and is expected to hit that in the hotter TX markets next year, taking advantage of some newer lower-cost lower-labor panel racking technology coming out of India, released to production just this year.)

    BeOpt is a pretty good energy use download freebie (courtesy of the US D.O.E.). The PassiveHouse US (PHIUS) spreadsheet tools work too, and are pretty cheap. There's a learning curve, and garbage-in==garbage-out with a lot of these things, but it's better to spend the time now than the money later, if the whole thing is going to be DIY. This is a well-trodden path- there is a lot of information out there, but finding the optimal bang/buck requires actually using it, not just comparing performance specs between different types of solar thermal, none of which are truly appropriate. Get the load down to next-to-nothing first, and the size & cost of what it takes to handle the load become affordable. High performance building envelopes aren't very sexy technology (and rarely subsidized) but it's the necessary first-step for off-grid.

  6. #6
    Master Plumber master plumber mark's Avatar
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    the best off the grid system you could devise is a system
    that can caputre the sun during the day....passive air type
    solar panels that would be facing the sun on one side of your
    home....pumping the ari slowly through the panel and heating
    up the whole home during the daytime hours...

    . thick outside walls insulated with spray foam insualtion
    6 -12 inches thick ...and tripple pane windows.....

    this is very simple stuff to do.... you can literally heat a home with a
    wood burning stove if it is strategically located on a lower floor
    for pratically nothing per year.....

    their are more complicated passive and active air systems that.
    use a underground storage area of solar rock that holds the heat from the.
    day and can be used all night long.....


    keep it simple grass-hopper



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