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Solar collector exploded view and repair (hr)

hr
hr Member Posts: 6,106
in THE MAIN WALL
a few calls from contractors wanting to know about building panels, etc. I recently scored some nice 5X10 panels. i suspect rough handling caused some of the leaks.

Construction is fairly simple with a 1" copper header and 1/2" "rungs" running the 10 foot dimension. Fairly easy to build if inexpensive used ones are not around your area. I have a bid on 25 of these. Wondering how many may be damaged, however.

I used the REMS collection of tools, again, to fab a new piece to replace the damaged section. A tee puller and end swedge tool were used.

These panels have nice extruded boxes, tempered glass coverings and good gaskets. Insulation is a bit ragged, mostly the foil covering. I may use some Refletix bubble foil over the old stuff. Still well worth some repair time for the amount of energy they will provide me.

Any ideas of temperature rating for Refletix? These are sample rolls from the local distributor.

hot rod

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Comments

  • Mad Dog
    Mad Dog Member Posts: 2,595
    As usual...HR you are cutting edge

    no comment.....I keep my mouth shut when I should. I'm learning! Mad Dog

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  • ScottMP
    ScottMP Member Posts: 5,882
    Nice progression

    with the photos.

    I was thinking along the lines of more serpentine pipe work, but I guess the rungs are the way to go. Thanks for the photos, I'll post mine when I build the boys pool heater panel.

    Happy New Year

    Scott

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  • bill clinton_3
    bill clinton_3 Member Posts: 111
    insulation

    Hot Rod: I don't know the rating of reflectix: I do know a stagnating solar collector can reach the mid 300 degree range, so I'd be surprised if any bubble foil could handle it.

    Bill
  • Brad_3
    Brad_3 Member Posts: 24


    I wish I had those tools when I was repairing collectors after the freeze in San Diego in 1986(?). I just silver soldered most of the tears together, not always sucessfully.

    Many of the better solar collectors have black chrome surface treatment which is low-e, meaning it won't radiate the heat back to the sky, helping efficiency, especially when it's colder out, not necessary in warm climates. The collector plate gets hot by absorbing visible light from the sun and can then re-radiate it as heat (to the glass and then to the sky). Most commercial collectors also have low iron (water white) glass, increasing light into it by about 8%(?)percent if I remember correctly.

    A stagnant collector can reach 350 F plus, so I doubt very much if the bubble sheet would hold up. Also if you use common black paint, it may evaporate or degrade and give off fumes that will condense on the inside of the glass blocking the sunlight. Degrading insulation will do the same, binderless fiberglass is always used. Some problem with foam insulation too, which is why a good aluminum sheet on the exposed surface is good if there is no fibergalss in between the foam and collector plate.

    Having a good bond between the collector plate and the riser tubes is even more important than in a radiant floor. They are usually welded, but sometimes silver soldered, or less often wrapped tightly around the riser. Soft solders will melt and are pretty much worthless. True of the plumbing also, it all has to be brazed or silver soldered.

    My favorite control strategy is to use a small solar panel and directly DC powered pump. The Hartell pumps are apparently not available anymore, so it would be just the El Cid to use now (I'd like to hear about any other DC pumps around). Or I've heard that the Tekmar 155 works well in AC powered systems.

    Brad
  • Duncan_8
    Duncan_8 Member Posts: 2
    Forget polyethylene bubble foil hot rod.

    My guess is you'll have a molten mass of plastic pooled in the bottom of the collector. What temperature is PEX (cross-linked polyethylene) rated at?

    All the flat plate collectors I've worked with had a one-piece layer of unfaced spun fiberglass batt, about an inch thick, directly between the plate, and a sheet of foil-coated isocyanurate behind that. Don't ask me where they got four and five foot wide rolls of fiberglass insulation. Like Brad says, the heat from the collectors will cause the isocyanurate to outgas and eventually cloud the glass inside the collectors. But it wipes off.

    Drainback system is still the best, in my book. Half inch risers are a good thing in some respects. Most of the 4x8's have 3/8" or smaller risers, and the smaller diameter could trap water by capillary action when they should have drained. Then they would freeze and split. This was the most common failure I used to see. We'd squeeze the split together with a pair if channel locks or vise grips, then silver braze the crack shut.

    I have to disagree with Brad on brazing outside the collector box though, even though brazing was required by code in Denver. Never had problems soldering collector-to-collector with 95/5. Realistically, if you ever need to remove a collector from an array (like when you remove them for re-roofing?), we used to sawzall the couplings in the middle, then de-solder the joints. I have seen copper sheeting that was soldered to the risers crumble over time, though. I've seen the expansion and contraction of long panels saw cuts in copper over time where metal met metal, too - good gaskets are a good thing.

    Hey old man, I'd recommend 4x8 panels, (and a boom truck if you're on a roof) they're a lot easier to muscle around. ;-)
  • hr
    hr Member Posts: 6,106
    Good info, thanks!

    I do know from first hand experience that Pex doesn't work for solar. This was a piece of 1" I used to connect some panels. Sounded like a gun shot when it ruptured.

    These plates and tubes do have a coating, took a lot of sanding to expose copper to solder. I used a silicone adhesive to attach the caoted copper panel back onto the tubes??

    Hey Duncan, New Years greetings. Yeah, this panel will go up with the use of hydraulics :)

    Is you heat sourse condensing yet? :)

    hot rod

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  • Bryan
    Bryan Member Posts: 3
    dc pumps

    Brad
    I am using these pumps for radaint systems. They are originally designed for solar applications. This may be the same unit noted El Cid. I have them available from a supplier in Flordia.
  • Brad_3
    Brad_3 Member Posts: 24
    Ivan Labs

    Bryan,

    That's it, the El Cid pump by Ivan Labs in Florida. They're only 10 watts 12 or 24 volt DC, or can use a wall cube and rectified AC. It just uses a March pump end and creates a field that drives the magnetic coupling, an ingenious design. I'm also using them as loop circulators in my radiant floor. Only 50 watts with all 5 running.

    Brad
  • Brad_3
    Brad_3 Member Posts: 24
    Brazing

    I meant just the connections inside the collector need to be brazed, soldered joints work fine on the outside plumbing. I've heard that a stagnant collector will melt joints close to the collector but have never seen it. Probably not with the solders in use now.

    Brad
  • Brad_3
    Brad_3 Member Posts: 24
    silicone

    Hot Rod,

    I think silicone will take the temp, and will conduct heat better than air! Keep it as thin as possible, you already know that.

    Brad
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