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covering a evac tube system

rt_2
rt_2 Member Posts: 86
I'm planning on going on a vacation next winter for about 2 months and I'm wondering what I can do for shutting down my evac tube systrem without draining it down. I'm conserned in case I loose power for a few days and I'm not around to do something.  I'm looking for something (cheap) that I can use to cover the tubes. I thought of using a silver tarp but I'm a little concerned that if came loose and the wind started blowing it around, it may damage some of the glass tubes. Anyone have any  ideas. I'd love to find someting that would snap over each tube like maybe a very thin wall PVC pipe split lengthwise. Thanks for any ideas. 

Comments

  • hot_rod
    hot_rod Member Posts: 15,410
    a cover

    you could have an awning or boat cover manufacturer build a cover with elastic band to cover the entire array.



    Or if the tubes are heat pipe style, simply unplug them and store them somewhere safe. I built a rack on the ceiling of my shop to store the tubes, drilled some plywood with a hole saw for a hanging rack.



    I'm not sure you would need to remove them in the winter months if there is a heat load? I would be more worried about summer month overheating when the heat load is gone.



    A dump zone is another option but it would cost you you some electricity to run the pump and "dump" the excessive energy.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rt_2
    rt_2 Member Posts: 86
    edited February 2011
    cover

    Thanks Hot Rod,

    I kinda like the idea of some sort of cover. I don't like the idea of removing 50 evac tubes with heat pipes off a  extension ladder. 30 years ago I would have done it without even thinking about. I'm not getting any younger. 62 now.

    You talk about heat load during winter months. I'm concerned about loosing power for a few days which would not be uncommon for us in New Hampshire and the fluid just boiling away through the high point vent at the collector. 
  • hot_rod
    hot_rod Member Posts: 15,410
    other options

    Depending on how often you expect power outages and how much $$ you want to spend on protection from the arbitrary :)



    You could install a small 30W PV panel and a DC pump, depending on flow and pressure drop. What pump is running the system now?



    Or a battery backup system to power the pump you have.



    Same issue with wood fired boilers when the power goes out. I've seen a deep cycle battery with a trickle charger used for back up, either with a DC pump in series or through and inverter to run the pump you have. But the power to keep the battery up and the loss through an inverter will eat into your solar savings.



    I've also seen some dump zone fin tube installed alongside the array and a 3 way thermostatic valve used to divert to the dump radiator.



    The glycol can take some ocassional over-heating.



    Tyfo makes a special ultra high temperature glycol, Tyfocor HTL or LS for evac tube use.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    Steamback!

    Siggy has described the expansion tank sizing method needed for steamback.

    The collectors will evacuate themselves upon stagnation, and the PRV won't pop if the expansion tank is large enough. Evacuated tubes are nice for this method because they have a small volume in the collector, meaning a smaller expansion tank.



    See http://www.heatinghelp.com/forum-thread/133064/Steamback-System-Design
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • rt_2
    rt_2 Member Posts: 86
    cover

    I already have a battery backup. I tied the pump into my battery backupo for my pellet stove. It has two deep cycle batteries.



    rene
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Turn 'em, don't burn 'em...

    Some evac tube collector receivers can be turned 180 degrees so that their absorptive surface can't see the sun directly....



    When you get back, flip them back over. Have heard of people flipping every other one over during the summer months to limit storage tank temps.



    Not all evac tubes are built equally.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • rt_2
    rt_2 Member Posts: 86
    rotating

    Thanks for your reply Mark. I can't rotate mine. The evac tube glass is clear the full 360 degrees. Turning them wouldn't do anything. Thanks anyway.

    rt
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