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Evacuated Tube Copper Pipe Seized in Collector

Zxcv1984Zxcv1984 Posts: 9Member
Good day,

I have a roof mounted evacuated tube water heating system. I need to temporarily disassemble the system (roofing problems that need to be fixed). Many copper pipes (the pipes inside the evacuated tubes) are stuck in the collector and I can't pull them out. Anybody has experienced this before? Any tips or trick to disassemble them? Any help is appreciated.

Here's what I've tried up to now:
1)WD-40: sometimes helped, but won't free the hard cases, which are many;
2)Working at sundawn, with the system completely cold: does help, but again won't free the hard cases;
3)Working with hot tubes: doesn't help at all AND very inconvenient (very high copper tube temperature) AND maybe safety issues;
4)pushing the pipe further in, then pulling out: does help;
5) Brute force: I have applied limited force in order not to damage the collector. As it's still mounted on my roof and I haven't removed the covers on the collector to confirm its construction, I'm playing it safe and have only applied the force one could apply without the help of tooling (otherwise said: hand force).

I'm thinking of trying penetrating oil, but I'm a bit help back by the potential fire hazard.
I'm thinking of finding something I could use to dissolve the old thermal paste, however this IMHO will be a last resort, as I doubt it would work and the product that COULD work is hard stuff for many plastics (e.g. acetone...)

Comments

  • Larry WeingartenLarry Weingarten Posts: 1,508Member
    Hi, I have run across this and it was caused by the header freezing and pinching the top of the tube. If you could wiggle the tube to try and loosen it, that might help.
    Yours, Larry
  • hot_rodhot_rod Posts: 11,608Member
    what about removing the entire array without pulling the tubes from the header?

    Or try ice around the condenser tube to shrink it from the header

    The hotter the tubes the more they expand
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Zxcv1984Zxcv1984 Posts: 9Member

    Hi, I have run across this and it was caused by the header freezing and pinching the top of the tube. If you could wiggle the tube to try and loosen it, that might help.

    Yours, Larry

    "Freezing" like freezing the water in the collector from cold during winter time?
  • Zxcv1984Zxcv1984 Posts: 9Member
    hot_rod said:

    what about removing the entire array without pulling the tubes from the header?



    Or try ice around the condenser tube to shrink it from the header



    The hotter the tubes the more they expand

    That's a good idea. The thing is, the array structure hasn't been designed to be lifted whilst completely assembled. I looked at it myself and asked the opinion of a few people around, and although everything's possible, this solution would require some work to support / strenghten the array structure so it's not damaged when I bring it down. Additionnal detail: just because of where the building is situated, we doubt we can access it with a telehandler, we'd be looking at a small crane to lift it from the top. I might end up using this solution, however I'm looking for alternatives for now.
  • hot_rodhot_rod Posts: 11,608Member
    What brand, if I may ask? A heat pipe of flow thru design?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Posts: 1,508Member
    Hi @Zxcv1984, I've dealt with freezing water in the insulated header at the top of the tubes. This picture doesn't get it well, but you might see the copper bent in some.
    Yours, Larry
  • Zxcv1984Zxcv1984 Posts: 9Member
    @hot_rod : Sunmaxx collectors. Heat pipe design.
  • Zxcv1984Zxcv1984 Posts: 9Member
    @Larry Weingarten Thanks Larry, there's nothing like a picture. The heat transfer medium in my system is water. Not glycol, just straight demineralized water. We do get very low temperature (way below freezing point) at my latitude. My system is designed to drain completely whenever the temperature sender reads a temperature below a certain setpoint. I need to investigate on what would be the consequences of a broken temperature sender or an electric power failure (does the system flushes or not? Both scenario could help or do harm, depending on the season.) That could explain some things.
    I just moved in this house last January and am still in the process of learning this system, which is very effective, but all new to me.
  • hot_rodhot_rod Posts: 11,608Member
    Is its a drainback system, the collector drains down when temperature is reached?

    I have not see a good design for completely draining the header? So even a small amount of water in the bottom of the header could freeze and cause damage.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Zxcv1984Zxcv1984 Posts: 9Member
    When the set temperature is reached (high enough to pump heat from the collector and transfer to the tank), the pump pushes the transfer medium from the tank to the roof. When the set temperature is hit again (e.g. after the sun sets, clouds, etc.) the system drains by gravity. I haven't checked closely, however as the bulb ports (the part where you slide the copper bulb in) is thin walled, I understand how this could happen. I'll take a closer look in the light of what we just discussed. If all this proves to be what really happened and my bulb ports are wrapped, I'm bound for a good job of tearing off stuck copper pipes the hard way, re-shaping the bulb port (not sure how I'd proceed, just thinking out loud), then fitting in new copper pipes. :D
  • Zxcv1984Zxcv1984 Posts: 9Member
    As for the setpoint, I know it's dependent on the accumulation tank temperature, however I'd have to check if it's dependent on other parameters. But I digress... Kind of like to learn about how this setup works. :smile:
  • hot_rodhot_rod Posts: 11,608Member
    Basically two types of solar thermal being installed currently. A pressurized system, typically with glycol antifreeze protection. In some climates plain water is used, on the equator for example :)

    A drainback would have a separate small tank that allows the fluid from the collector and piping, usually a 6 gallon size tank.

    I much prefer drain back as it eliminates over-heating of the glycol which can break it down in a few years time.

    One issue with evacuation tube drain back is the condenser bulb in that well with no fluid flowing across it can reach 300°C, reflector type up to 350C, according to German lab tests.

    Look into the Dow high temperature silicone grease. The grey zinc oxide or silver based paste tends to harden and glue components together. Happens with any copper sensor in a well after time.

    The very best thing is keep a constant load on evacuation tubes, when the stagnate things get hot in a hurry.

    Here is an Oventrop tube making tea water on a cold winters day.

    Also a journal we produced on solar thermal basics.

    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_3_0.pdf










    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Zxcv1984Zxcv1984 Posts: 9Member
    @Hotrod Thank you! Is the DOWSIL™ SC 102 Compound the product you refer to when you speak of DOW thermal paste?
  • hot_rodhot_rod Posts: 11,608Member
    Zxcv1984 said:

    @Hotrod Thank you! Is the DOWSIL™ SC 102 Compound the product you refer to when you speak of DOW thermal paste?

    I'll check with our lab on Monday. I remember it being clear, almost like a squeeze tube of silicone.


    You might also contact DOW directly at the link they show at the bottom, explain the application. Often they send samples.

    Or small tubes are also found on Amazon, once you get the correct part #.

    https://www.ellsworth.com/globalassets/literature-library/manufacturer/dow-corning/dow-corning-brochure-enhancing-the-reliability-of-your-electronics-designs.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Zxcv1984Zxcv1984 Posts: 9Member
    I gave a call to DOW early this week, they recommend DOWSIL™ SC 102 Compound for the application. I'll give it a try. Thanks again!
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