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Drainback EV tube header

oldsolaroldsolar Member Posts: 7
I want to use a Sumaxx evacuated tube Thermopower VHP- 20-30 in a water drain back system in Maine. Can I get the header to drain completely to avoid breakage or is it too convoluted with fluid traps like the Viessmann and others. Any thoughts would be great.


  • rtrt Member Posts: 86
    evac tubes

    I have (2) twenty five tube collectors in southern NH. My system is filled with glycol. If it was filled with water, I believe it would drain with no problem. My system is pretty much perfectly level and I think it would drain back OK. If you're concerned, just put a little bit of pitch when installing it or fill it with glycol.

  • Kevin_in_DenverKevin_in_Denver Member Posts: 588
    edited November 2012
    Sun Maxx is pretty much a straight tube

    rt is right, it will drain back no problem.

    Apricus has a little convolution, and Thermomax/Viessmann is very convoluted and risky to drain back.
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • oldsolaroldsolar Member Posts: 7
    Header shape

    Thanks for the info on the header. I finally found a cut-away drawing of the Sunmaxx Themopower which confirms the straight tube configuration. The same drawing applies to the Sunmaxx Thermopower and the Sunrain EV tube collector. I guess Sunmaxx gets them from Sunrain.
  • rtrt Member Posts: 86
    edited November 2012
    Evac Tubes.

    I hope that SUNMAX has depleted there stock of heat pipes purchased from Sunrain in the last couple of years. I don't know if you read one of my earlier posts (last winter) where I talked about the issue of heat pipe splitting by freezing. What I found that out of 50 tubes, 1/2 of them weren't working because the heat pipes froze and split and all the liquid leaked out thereby rendering them useless. After many E-Mails directly to Sunrain, they did respond by shipping me 50 new heat pipes. They also said that they changed the formula of the liquid inside the heat pipes. They would not reveal what the liquid was. Talking with one of SUMAX's Reps 1 couple of years ago, he told me that they were trying to develop a heat pipe to be manufactured here the the US. I don't know where they stand on this. It may be a question to ask. If you get any info, please pass it on tFebruary 19, 2011o us.

    Update: My earlier post is on page 2, and nearly all the way down. The date was February 19, 2011 and the tilte Is "BROKEN EVAC TUBE". Interesting post and lots of good info from allot of people. 

  • oldsolaroldsolar Member Posts: 7
    Sunmaxx EV in hand

    I have the Sunmaxx VHP -20 in hand. From cutaway drawing I thought the header was straight through, so much so that you could probably see light from one end to the other. Not so. No light. Header outlets 1”, header probably 1 ½”. Poured water in the end at ¼” foot slope. Water came out but not all of it then later some more came out. Conclusion, probably will drain but I’m scared to try it in Maine. Still committed to drainback so, as others have suggested it will be a glycol mix for now. Will start new thread on glycol questions.Thanks all.
  • Kevin_in_DenverKevin_in_Denver Member Posts: 588
    Sun Maxx is OK for Drainback

    I tested it down to -15F in Denver.

    Freezing splits only occur in full pipe or pipe that is more than 90% full.

    Messing around with glycol is a waste of time and energy because it is less efficient than water.
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
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