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A/C "High Pressure" fix

Discussion in 'Technical Discussion' started by CTdave, Aug 30, 2015.

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  1. CTdave

    CTdave Senior Member

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    I learned something about air conditioning repair today & I thought I'd share.
    I had three completely new systems installed in my 50 Hatteras this spring & everything worked perfectly till yesterday.
    The main system in the salon was the only unit running but it suddenly stopped. The control panel read "HI PS" for "high pressure". I emailed my a/c installer & he said that 99% of high pressure issues stem from a lack of water flow & to check:
    Water flow where it exits the side of the boat.
    Check the strainer and intake.
    Check the pump.

    I noticed there was a fraction of what normally exits the boat so I shut off the sea cock & took out the strainer. It was clean. Then while it was open, I opened the shut off to see what the flow of water was like coming into the strainer. Very little! I put a hose into the intake pipe to try & flush it out but the water flowed our perfectly. Removed the hose but again, little water coming in. I had a 3/8' piece of rubber hose so I pushed it into the intake pipe & just before it hit the grate/exterior strainer, lots of water flowed. I knew what it was!!
    I jumped overboard with a mask & within a second I saw the culprit. A plastic bag!
    I pulled it out, problem solved!

    So remember, "HI PS"= bad water flow.
    I know from my old system that "LO PS" (low pressure) always meant the refrigerant was low from a leak. Call an a/c guy!
  2. K1W1

    K1W1 Senior Member

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    LP can also be the Evap ( thing with the fins) freezing
  3. Capt J

    Capt J Senior Member

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    Which is caused by low freon or in some rare cases an extremely dirty air filter or bad blower motor.
  4. Pascal

    Pascal Senior Member

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    Yeah that pretty common, plastic bags will get stuck in the inlet but only kill flow when under suction. Tricky. Usually when you open the strainer they will let enough water to flow in but once you start the pump they get sucked in tight

    Another increasingly common issue in Florida are little mussel like shells growing in hoses and manifold.
  5. Capt J

    Capt J Senior Member

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    This is a rather new phenomenon that I saw start to pop up about 3 or 4 years ago. The first time I came across this was on a yacht I managed and they had packed the strainer, and all of the lines all of the way to the discharge. We had to acid wash everything and circulate it and it took a lot of time to get them all out. I put a couple Bromine tablets in the sea strainer and then clean the strainer monthly an add them and it seems to keep them away.
  6. Capt Ralph

    Capt Ralph Senior Member

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    In Jax, all the run-off, pollutants, fertilizers, road trash and old back yards have created a foul similar to Berber carpet with barnacle larva attaching to that. In a month over the best of fresh paint the diver is scrapping instead of wiping the sediment off.
    If the boat is not used, that SpeedProp stuff is useless.
    When this crap gets into the A/C lines, It's not pretty.
    Hot, dark A/C water and HPF errors are everywhere.

    I can't complain to much. It keeps a few of us up here busy.
  7. Pascal

    Pascal Senior Member

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    Problem is that normally you only descale the coils

    On the johnson 70 I run we were getting reduced flow on some of the ACs because of the discharge lines which run aft to TH that were impossible to reach.

    I had to enlarge access panels, and replace the standard seacocks with three way valves so we can hook up a flushing lines to descale the whole thing. Major pita

    The other issue is that they die during a haul out and then pile up at fittings when you restart the systems. I had a manifold completely full of the little buggers after the last haul out
  8. Capt J

    Capt J Senior Member

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    If you put 4 bromine tablets in the sea strainer once a month, they'll last about a week and kill off any of the larvae throughout the entire system and discharge lines and never get to the mini mussels stage to clog anything.
  9. Capt Ralph

    Capt Ralph Senior Member

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    We have mixed reactions with the tabs also. Frost the clear acrylic strainer tubes and makes nylon and forspar fittings brittle.
    A part of our inspections & service is using a round tollette brush to clean the strainers and shop vac out any silt on the bottoms.. We can see the frosting starting where the bromide tabs were in use.
    We had some customers try to use the tabs in sumps and bilges. It does keep them clean but will eat up the bottom plastic on a rule pump in about a month.
  10. K1W1

    K1W1 Senior Member

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    Anyone looked at ultrasonic or cathelco type units?
  11. Capt J

    Capt J Senior Member

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    Bromine tablets or Chlorine tablets? I haven't seen any such issues with Bromine tablets, not to say that it's not incurring, but I have not seen it in years of using them in various yachts.
  12. Capt Ralph

    Capt Ralph Senior Member

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    We service a couple of boats up here that do not have Perko / Groco type strainers. All metal without acrylic components. I guess they could be better candidates for bromide tabs.
    Of interest an ole Southern Cross MY (last of 8 imported) with pretty stainless strainers. These big shinny assemblys don't seem to foul internally so much. Could be the center fed design, materials or because we work to the owners rotating schedule @ 3 weeks service intervals and all other boats at 4 week.
  13. Bamboo

    Bamboo Senior Member

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    copper plumbing elbow fittings from Home Depot go into my a/c strainers. No growth.
  14. Capt Ralph

    Capt Ralph Senior Member

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    Hummm, I have heard this before.
    AND, I have a box of old brass and a bunch of fouled strainers (MINE).
    New test a coming.
  15. Capt J

    Capt J Senior Member

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    Brass and Copper are two different things.....Copper is what they used in bottom paint for years.
  16. Capt Ralph

    Capt Ralph Senior Member

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    Your rite, I read/typed to fast. Thx.
    Got lots of solder on copper junk also.
    We have lots of strainers, lots of junk, some time.
    Just gotta crawl out of other bilges and back into my own.
  17. Capt Bill11

    Capt Bill11 Senior Member

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    You mean like a Zeta Rod? http://zetarod.com

    Had one on a Marlow once. Seemed to work. But they are expensive as I recall.
    Last edited: Sep 6, 2015
  18. K1W1

    K1W1 Senior Member

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  19. gr8trn

    gr8trn Senior Member

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    Thanks for the clear explanation of steps taken and glad you found the solution, would be super annoying if your new system had a mechanical failure.
  20. K1W1

    K1W1 Senior Member

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    Not an unknown phenomenon on yachts and other complicated things