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How do I clean the inside of solar panels

Big D_2
Big D_2 Member Posts: 5
I have some used hot water solar panels that have been out of service for 5 years. They were drained (although I don't think very well),and sitting on the roof. I have rebuilt them, but when I was flushing them out a bunch of gunk came out. I flushed them until the water ran clean, but I am sure they still have some baked on anti-freeze inside the tubing. I would like to get the inside of the collectors as clean as possible to have the most efficient heat transfer. Does anyone know of a liquid I can use to clean them out. Would boiler cleaner work, or some sort of mild acid?


  • hot_rod
    hot_rod Member Posts: 21,826
    hydronic cleaners

    like the Rhomar product, or the coil cleaners like Hercules Sizzle (follow dilution procedure with acid cleaners)

    Or if the build up is not real bad, TSP or a dishwashing liquid.

    It helps to keep the panel and fluid warm to clean better with soaps. Set the panel outside in the sun, get a 5 gallon plastic bucket and a small submersible pump and circulate through the panels for the day. That's the method the works well for me.

    Don't over do the acid % if you use Sizzle or other acid based cleaners or you may pin hole the copper. Soaps and hydronic cleaners are easier and safer if it will cut the crud.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853

    If the crud was laid in place during circulation, it is helpful to run fluid through the water ways backwards in comparison to what it use to be. Corrosion "lays in" with points pointing in the direction of flow. If you forcefully run water through the corrosion backwards at a high velocity, it "breaks off" a lot of the corrosion.

    Loosen it up with soap first, then during rinse, using high pressure (city water pressure if you have access) back flush the water ways, then forward flush, one last back flush, followed by final forward flush. You will be amazed at what comes lose.

    Take pictures :-)

    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.
  • Rhomar Mike
    Rhomar Mike Member Posts: 11
    Cleaning solar panels

    The Rhomar cleaning fluid that Hot Rod was referring to is HydroSolv 9100.Environmentally friendly, effectively cleans aluminum,iron, copper,brass and stainless.

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