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a new twist on an old cap

hot_rod Member Posts: 19,289
The Coolie Cap has been around for some time as a means to flash copper tube thru the roof. Here is a solderless version I built.

I need to install a 1/2 and 3/4 copper line thru a corrugated metal roof, ideally with just one penetration, for a drainback installation.

This cap was built with a 3" copper cap and a couple Viega pro-press couplings cut in 1/2. I learned after the fact that Viega offers extra long repair style couplings the would work nicely, no center stop to work around.

With a holesaw I drilled the two couplings and the sensor wire gooseneck holes. I removed the o- rings to silphos the couplings into the holes. I'm searching for a few of the Viega high temperature o-rings to install in the couplings. So the tube can now expand and contract in the o-ring seal and still provide a water tight seal.

I have a scrap of stainless AL 29 vent pipe to set the cap on and extend down into the attic space. I'll post completed pics when the roof cools down enough to get back on.

Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream


  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    pipe size?

    Nice looking job, hr, how many feet of 1/2" pipe is recommended on the downcomer?
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • hot_rod
    hot_rod Member Posts: 19,289
    I have

    two 3X6 collectors flowing maybe .85- 1 GPM each so 1/2" will handle that. 1/2" copper needs about 1.6 GPM flowrate to establish 2 feet per second velocity. At that speed it will move the air bubble along nicely. About 8 feet from the drainback to the top of collectors.

    I have seen some drainback systems on the market piped with 3/8" copper tube.

    I worry how well that small tube might drainback especially on the horizontal runs in cold conditions. 15mm is a common tube size used in Europe for DB linesets, just a tad under 1/2" CTS.

    I came into a couple brand new 30 year old never installed Revere collectors. These babies had some serious copper inside them. The absorber plates are .030 thickness copper and weigh just under 30 lbs. They were built with a very unique connection from the tubes to the plate.

    Here is a shot showing the backside with the chrome finish, and the front with the black applied over the chrome.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Got patent attorney???

    I'm hoping you CYA'd yourself and at least sent documentation to yourself noting your idea and the date conceived.

    Nice find on the solar collectors. Surprised Siggy didn't offer to buy them from you. He probably had something to do with the design and or construction of same.

    Reminds me of the fabled old stories about finding a perfectly new (place item here) in an old farmers barn :-)


    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.
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