Cleaning Schuco panels internally

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  • Ben25
    Solar Fanatic
    • Jul 2014
    • 135
    #1

    Cleaning Schuco panels internally

    I have a customer with 3 schuco panels that have been sitting for a few years. When I went to pressure test, I could barely get any air through the panels. My guess is that the glycol boiled off and turned to goo inside the serpentine coil in the panels. Has anyone found an efficient way of cleaning this out? I tried water with air pressure behind it with no luck. I'm most likely going to replace the panels on this one, but would be nice to be able to salvage others.

    Ben
    Tags: None
    • J.P.M.
      Solar Fanatic
      • Aug 2013
      • 14995
      #2
      Originally posted by Ben25
      I have a customer with 3 schuco panels that have been sitting for a few years. When I went to pressure test, I could barely get any air through the panels. My guess is that the glycol boiled off and turned to goo inside the serpentine coil in the panels. Has anyone found an efficient way of cleaning this out? I tried water with air pressure behind it with no luck. I'm most likely going to replace the panels on this one, but would be nice to be able to salvage others.

      Ben
      Whatever is inside the tubing, if it's enough to prevent fluid flow, it's probably substantial. What type of glycol is it ? Ethylene or propylene ?

      Either has a very low vapor pressure and will probably not evaporate easily, particularly if the collectors were stagnated under pressure. BTW, depending on the glycol type, concentration and pressure, and the relieving device type, the solution may not have boiled off. It may have simply dropped in PH and corroded the inside of the tubes. Then, depending on the tube material and a lot of other conditions, that process may have passivated the remaining tube material as a form of some protection from further corrosion. Hard to say.

      Since the Ph of glycol goes down as it ages, you may have some chemical corrosion that developed over time with the corrosion products migrating under gravity to a corner or some such low spot(s) and plugged the flow.

      Critters, particularly cats, like ethylene glycol as it's sweet. Maybe some critters (bugs) got into the tubeside. Don't know why, but butterflies (and caterpillars) seem to love the stuff. Long story on how I found that one out.

      Fouling on the glycol side of industrial heat exchangers is seldom necessary because the glycol /H2O mixture is usually monitored for transport property changes and also for Ph, and so gets changed out regularly. On the rare occasion when the glycol side is fouled, I recall glycol ether solvents being tried, but I don't know what the exact type of several that was tried or what the outcome was. Most glycols are also soluble in organic solvents, like methyl alcohol, acetone, methylene chloride, etc., but that begins to get into environmental and toxicity issues.

      Maybe as a science/curiosity project you could sacrifice one of the collectors, cut it open and see if/where/what the corrosion/fouling looks like and experiment on what, if anything seems to get rid of the fouling.
      Last edited by J.P.M.; 09-26-2018, 10:33 AM. Reason: Corrected glycol Ph statement - the Ph of glycol goeds down with age, that is, it becomes more acidic. Apologies for the misstatement.

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        • Mike90250
          Moderator
          • May 2009
          • 16020
          #3
          I'd try acetone for a week on one, flood as much as you can into it, check every hour to see if you can get more in, and they see what drains out after a couple hours. I'd try that before cutting one open
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            • LucMan
              Solar Fanatic
              • Jul 2010
              • 626
              #4
              Scrap them they are junk. Even if you can get some flow through them the glycol had turned acidic long ago etching the walls of the tubing. They are going to leak if put back into operation

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                • Ben25
                  Solar Fanatic
                  • Jul 2014
                  • 135
                  #5
                  Took the 3 old Schuco panels down yesterday and replaced with 1 new Viessman. (Lower usage now than previously)
                  I cut into one of them on the bottom of the vertical loop and found the problem. The glycol had boiled off and turned into a substance with the consistancy of coal, completely clogging the line. That copper is super thin as well, so wouldn't take much etching to spring a leak. Didn't have time to try any acetone, I gave them to my helper to scrap.
                  Attached Files
                  Last edited by Ben25; 09-28-2018, 07:03 PM.

                    Comment

                    • J.P.M.
                      Solar Fanatic
                      • Aug 2013
                      • 14995
                      #6
                      Originally posted by Ben25
                      Took the 3 old Schuco panels down yesterday and replaced with 1 new Viessman. (Lower usage now than previously)
                      I cut into one of them on the bottom of the vertical loop and found the problem. The glycol had boiled off and turned into a substance with the consistancy of coal, completely clogging the line. That copper is super thin as well, so wouldn't take much etching to spring a leak. Didn't have time to try any acetone, I gave them to my helper to scrap.
                      Check the price of scrap copper. Last time I turned some in (~ 120 months ago), it was going for ~ $2.05/lbm. A copper collector may have about 1 lbm/ft.^2 of copper in it. I have no idea what boiled glycol is going for, nor any idea how someone would do about finding it inside a closed tube.
                      Last edited by J.P.M.; 09-30-2018, 10:07 AM.

                        Comment

                        • LucMan
                          Solar Fanatic
                          • Jul 2010
                          • 626
                          #7
                          That's the problem with using glycol it requires yearly monitoring and replacement every few years. Most customers don't want to spend the money for yearly maintenance. Lets BBQ those panels !!! Don't forget the rest of the system took a beating from the corrosive glycol also.
                          They also don't want to foot the extra cost for the initial install of a drainback system that is virtually maintenance free.
                          Last edited by LucMan; 09-28-2018, 09:39 PM.

                            Comment

                            • Ben25
                              Solar Fanatic
                              • Jul 2014
                              • 135
                              #8
                              I'm one of the few people left in Vermont who service these things, and we are talking about getting out of it as well.

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