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    drainback tank ideas (4 Posts)

  • hot rod hot rod @ 10:46 PM
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    drainback tank ideas

    I built these for some single and two panel systems, short piping runs. The red one is a 4.4 gallon expansion tank, had a bad bladder. I perforated the failed bladder out with a long drill bit, and brazed some nipples in. This will replace a leaky tank at my house that was made from an old freon jug over 20 years ago. Pretty good service for a tank.

    The yellow one is an 11 gallon, portable air tank. Harbor freight $36.95. I added the nipples and sight glass. A bit thicker walled tank, compared to the expansion tank.
    Although expansion tanks are rated to 150 psi (before the modifications :) This will be a horizontal mount up in the ceiling joist.

    I use water heater blankets from the box stores, two wraps around for a 2" fiberglass insulation with a white vinyl covering. Limits heat loss and quiets them down a bit.

    A dash of glycol or some Rhomar inhibitor in the system helps protect ferrous metals.
  • RobG RobG @ 1:20 PM
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    Amazing

    HR, you are a mad scientist! How on earth do you find the time for your projects? How does the PEX work as a site glass? What pressures are you putting through it? Could you explain how you "perforated" the bladder out of the exp tank?

    Sorry for all the questions,
    Rob
  • hot rod hot rod @ 2:30 PM
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    always pondering

    ways to make affordable SDHW systems.

    I have used pex sight gauges for many years. I don't trust the acrylic or polycarbonate gauges, just not a good fitting available for them. Glass is best, but not easy to work with and expensive fittings. The fittings need to be perfectly aligned to use glass sight tubes.

    Uponor rates their pex at 200F 80psi. Rumor has it it can go above that temperature if the pressure is lower. I doubt you will ever see that in a spec, liability issues perhaps?

    I run 30 psi in the DB systems. That gives me about 270F boiling point, and assures some NPSH at the circ.

    Most solar control ship programed with a 270F lock out temperature. It may be adjustable on some models.

    I used a 3/8" drill bit, 12" long and drilled a bunch of holes through the bladder, down through the nipple.

    I'd like to buy some bladder-less expansion tanks with 4 nipples welded in. Zilmet builds a VSG tank with a nipple in either end, no bladder. IIt is intended as a cool down tank for evac tube systems, upstream of the bladder tank. Hard to find a dealer for that brand, however.

    I have been using used a weak PG solution, 30%. It gives me some color to see in the sight glass, inhibitors for the steel components, and some piece of mind should something cause the drainback piping to lose it's pitch.

    I can also set a min. collector turn on temperature for the plain water systems, but you still harvest energy in below freezing conditions with flat plate collectors, let 'em run all winter. Or lock them off a 10•F or something around there, unless you are using them for heating loads.

    For that yellow tank I found a piece of 1X12" fiberglass pipe insulation, 36" long about 20 bucks online. I can find that locally also. That will make a nice looking, high temperature insulation jacket. So I'm into this tank about 80 bucks and an hour or so labor.
  • hot rod hot rod @ 10:06 PM
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    finished look

    Turns out 11" IP pipe insulation has a 12" ID. Circles for the ends cut from sheet fiberglass stock, bubble foil covers for that NASCAR look.

    Aluminum saddle to protect the fiberglass when hanging with strap steel brackets.
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