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Flushing boat A/C lines w/muratic acid

Discussion in 'HVAC' started by CSkipR, Apr 28, 2011.

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  1. CSkipR

    CSkipR Member

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    Typically every year I flush the boat A/C lines to remove anything that may have attached itself to the inside of the copper lines by mixing 25% muriatic acid and water then circulating it through the system. I put the mixture in a 5gal bucket with a 500gph bilge pump. The bilge pump has a hose running to the ac water inlet side and another hose is attached to the water outlet side returning back to the bucket. I let it circulate for 3-4 hrs on each unit. This seems to work fine although it does not remove any residue from the AC hoses or the strainer. Is this a big deal?
    My question is there a simpler or better way of doing this and also does someone out there make a bucket with fittings on the sides for this purpose?
  2. C4ENG

    C4ENG Senior Member

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    I am sure there are many engineers shaking there head at you right now.

    When I acid flush heat exchangers, the first thing I always do is go very weak on the acid and I use only the acid sold for flushing coils from A/C shops, not the muratic acid, way to strong. Second you want to flush slowly so the acid can do it's work, not a 500 gph pump by no means.

    I have seen a lot of damage in the past caused by others acid flushing to much. I only do it if there are no other ways.
  3. C4ENG

    C4ENG Senior Member

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    This is the type of pump I use...

    http://www.marchpump.com/lc-3cp-md/

    Simply drop it in a bucket (or a plastic trash can) with the acid mix. I will have a hose attached to the pump and then a return line (hose) running back to the bucket held with a vise grip or anything like such
  4. CSkipR

    CSkipR Member

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    C4ENG Do you put the March pump directly in the bucket? By the way that pump puts out 8.5 gpm which is 510 gph or about the same as the pump I mentioned.
  5. tirekicker11

    tirekicker11 Senior Member

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    Interesting link to this magnetic pump.
    If used as a bilgepump would it mean that this motor can't burn out when debris stops the impellor from rotating?
    Wonder what the price difference is when compared to Rule.
  6. intheocean

    intheocean New Member

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    Muriatic acid to clean copper lines? why? That stuff is strong. Also, you need to let the acid (a much weaker one) like a sulfamic acid - not sulfuric, sit in there for a while. Lastly, I would prepare for new lines as acid of any sort can corrode the copper as well. Do you have alot of calcium deposits or something?
  7. happyendings

    happyendings New Member

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    hmm, sounds about right
  8. NYCAP123

    NYCAP123 Senior Member

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    I think C4ENG saw what I saw 500gpM. Some times the eyes play tricks on us. We see what we expect to see.:eek:
  9. Capt Bill11

    Capt Bill11 Senior Member

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    They are not self priming.

    As far as using acid to clean out coils goes, while I've used it for years in the past with no negative results, there are much better and safer products out there now to clean your coils with.
  10. Capt Bill11

    Capt Bill11 Senior Member

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    Yes you put it right in the bucket. Or at least I have. You can also use this system to clean out heat exchangers without removing them from the engine in many cases.
  11. tirekicker11

    tirekicker11 Senior Member

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    I find that to be the problem with most Rules I see too. The March pumps can be submerged so that should eliminate the problem.
  12. yotphix

    yotphix New Member

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    The March pump runs between 250 and 350. Great little pumps but if you just need something cheap to do this task alone they are a little pricey. Incidentally, A/C contractors love people who use Acid to clean their coils. A new 6 ton chiller runs 12-14,000 and the coils degrade quickly if subjected to this treatment.

    http://trac-online.com/index.php?pa...n=com_virtuemart&Itemid=62&vmcchk=1&Itemid=62

    That's what I have been using, on the promise that it won't eat metal. I'm sure there are other products but I can attest that this stuff will help all of the little mussels who like to grow in my area out the door.

    I use roughly the same procedure as you, with a rule 110v bilge pump I just drop in the bucket.
  13. C4ENG

    C4ENG Senior Member

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    Yes I did :)
    And I meant to find the link for a 5 gpm pump as well
  14. CSkipR

    CSkipR Member

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    AC line cleaning

    Here in Florida all the marine AC contractors I've used (3) before flushed the systems with muriatic acid. It maybe because Fl has alot more barnacles, scale, etc in the water than CA or other coldwater areas. Remember it is diluted to 20%. Too my knowledge never heard of any damage to ac lines from diluted muriatic acid. I have heard of a few people using barnacle buster with fair results. Thanks for all the input.
  15. Pascal

    Pascal Senior Member

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    Muriatic is string stuff and hard to dispose of properly

    Phospho is a good alternative and not as dangerous

    Not cleaning the hose, pump and strainer is fine, the issue with coils is that the deposits reduce heat transfer.
  16. Marmot

    Marmot Senior Member

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    "I am sure there are many engineers shaking there head at you right now."

    Maybe only at the concentration the OP claimed.

    Sulfamic acid with a "built in" pH indicator to let you know it has done its job is the safest and best alternative but a weak solution of HCL is not the worst thing you can do.

    I have used HCL to clean stubborn deposits from low pressure evaporators when I needed to get the unit back online quickly. Since there are viewing ports in those things it was easy to see when to stop the process, a benefit that we don't have on a small boat cooling loop.

    Too strong a concentration will remove metal and the fumes are dangerous to health as well as very corrosive to everything else in the engine room so it's a judgement call on when and how to use it.

    I don't believe there is much advantage to using it on a yacht when regular use of a safer product will accomplish the same end. It is safer and easier to store and use powdered sulfamic on a boat.
    Last edited: Apr 29, 2011
  17. Silver Lining

    Silver Lining Member

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    There are two companies that commonly sell descaling solutions for the marine industry, Barnacle Buster and Rydlyme. One is a phosphoric acid based solution the other is aqueous hydrogen chloride. They both dissolve calcium deposits, mussels, scale etc. They are both sold and used in a nominally 10% dilute solution and can be or are recommended to be diluted even further to a 5 % solution for marine descaling applications. Both companies add additional proprietary ingredients to enhance wetting etc.

    Both of the above companies sell complete recirculation systems from 5 gals and up, using appropriate pumps and materials. The pumps used to recirculate the solution should have viton valves and santoprene diaphragms based on chemical reactivity. Many of the cheaper pumps made for water will not stand up to repeated exposure to acids, and I would not want to dissolve and cover my heat exchangers with a rubber or polymer coating. Also the tank, hoses and external valves should be polyethylene or PVC.

    I assembled my system using a nice 10 gallon horizontal polyethylene tank with an external top mounted pump and PVC valves to shut off flow through the long hoses. Tanks, pumps, valves etc. used for chemical spraying in agricultural applications work very well in descaling applications since similar chemicals and acids are used. The agricultural/chemical spraying setups are low cost and use similar materials and pumps, that is what I used for the basis of my system. As stated above, the dilute acid only needs to be circulated slowly so a 1 or 2 gpm pump is adequate, in fact I stop circulation every 10 or 15 minutes for a few minutes to let the pump cool off a bit.

    While designing and assembling my system, I found a study by the US Navy looking at detailed comparisons of different acids for use as descaling agents. They extensively use descaling agents. The results showed both of the above chemicals worked well at the appropriate dilution and the biggest difference I noticed was that the two chemicals had a different effect on the native metal surface after descaling. The acids etch a natural surface layer that is formed by continuous contact between salt water and the typical metals used in heat exchangers. This layer affects the heat transport across the interface. It seems the reformation of this layer takes longer with phosphoric acid as compared to HCL, hours as compared to days, so it is probably not an issue in most marine applications.
  18. captbluewater

    captbluewater New Member

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    I use a Jabsco empeller pump that you attach to a drill motor. That way you can slow the acid going through. Let it sit for awhile then run it through at full speed. I then flush with fresh water. It is much cheaper if you already have a drill on board.
  19. Diversion

    Diversion New Member

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    For what it's worth I had an AC tech in S Florida who does a lot of Dometic warranty work, drain the strainer container, then fill up the container with the acid (cant remember the brand) and turned the system back on. Seemed to work well.
  20. Capt Bill11

    Capt Bill11 Senior Member

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    You should look into getting another A/C tech.