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Sunearth Sunsiphon and re-roofing

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  • Sunearth Sunsiphon and re-roofing

    I have a Sunearth Sunsiphon unit that I am trying to figure out what to do with as I get closer to replacing my roof. Because initially the system was not working properly (installed improperly) I ended up adding a gas tankless unit as backup with the solar feeding a thermostatic mixing valve into the tankless per manufacturer recommendation. It was an expensive way of finding out that the Sunearth installer had cross fed the input / output pipes to the tank. This was after a year of paying 2x electric bills and multiple trips out by the installer's company. Of course it was my tankless installer who pointed out the crossfeed and addressed it.

    The unit is about 6 years old and I am about to reroof and am wondering if getting a solar guy to take it down and put it back up is ever going to pay off for me. My wife and I have a pre-teen daughter and we don't use a ton of hot water. San Diego gas rates are reasonable and my gut tells me that the tankless is sufficient. I am wondering if my poor history with this thing is pushing me towards making a bad decision and would love to hear your input.

    If you have a tip on a solar hot water guy in San Diego I would also love to hear that via pm. Thanks.

  • #2
    If you already have a high BTU tankless that can process enough cold water, maybe re-installing is not needed.

    We have a rooftop preheater, and wintertime only get 80°F out of it, but that's better than feeding the tankless 35°F water. Summers, we feed 140°F, which is mixed down to 120, and the tankless at 115, never comes on. Just destroys the propane delivery guy's day.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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    • #3
      Having piped natural gas available certainly changes the ROI equation compared to the much more expensive propane. Electric tankless is really expensive too, as well as having an instantaneous power demand that may require a larger service for some people.

      You will eventually save money using a solar preheater with natural gas, but if the expense of removing and replacing the system is too high it might not be worth it for you.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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      • #4
        I've had 2 Sunearth 4 X 8 flat plates (but not thermosiphon) operating for 6+ years w/ no problems, save one minor leak due to an expansion joint gasket that had nothing to do with the collectors. IMO, the quality is good and the units are fit for purpose.

        Also, IMO only, If your units are plumbed properly in a correctly designed system, they should operate well and meet estimates of expected production.

        However, that says nothing about cost effectiveness of a reinstall in your particular application. Depending on the fuel used for backup hot H2O, the savings in fuel cost that production allows may or may not be worth the cost of fixing and reinstalling the system. If your source is CH4, and your annual demand for hot H2O is small, it may not be worth it, particularly with a tankless backup. If your heating source is propane and your needs are small, the cost of a refit and reinstall may also not be worth it. If your source is electricity to a tankless electric unit and your demand is large, or expected to grow a fair amount, I'd consider it.

        I suspect most installers might be reluctant to reinstall a system they did not initially install and/or in any case may will charge a fair amount to work on a system they did not install.

        It's too bad your unit was plumbed improperly. IMO, and not meant as a plug/endorsement/recommendation, Sunearth is pretty good stuff in DHW applications.

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        • #5
          Definitely leaning towards killing the thing and moving on with my life. One of the roofers offered to get rid of it for me if I drain it and make the plumbing disconnections. I would like to attempt to do this myself on the expectation that a service would be costly, and I might even have to ask the original installers back.

          I assume I could drain the heat transfer fluid by opening the valve at the bottom of the collector which seems to have a hose attachment. The method of draining the tank of water isn't intuitively obvious to me though. The water output is on the top side of the tank; simply running the hot water wouldn't seem to help. I have an instruction manual but it doesn't cover this contingency.

          What am I missing? I already have isolation valves to bypass the solar tank and go straight to my tankless, so this is the big question.

          And is there any value to a future owner in leaving the cold-hot roof penetrations in place when I re-roof? Does the term "solar-ready" mean anything to anyone?

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