Heat pumps

Discussion in 'Electrical Stuff' started by TomA, Apr 15, 2019 at 10:20 PM.

  1. TomA

    TomA New Member

    13
    May 24, 2018
    SeaRay 350 Sundancer, 1992,
    454 Mercruiser
    Hi, I have a 1992 SeaRay with two heat pumps for AC and heat. Can some one tell me what the plumbing is like? I assume the water is pumped to both units in tandem regardless of which one is turned on. When I turn on the forward unit it pumps water heats and cools. When I turn on the aft unit no water is pumped, the blower turns on but it doesn’t heat or cool. When I turn on both, the forward unit operates fine, but the aft unit just blows room temp air.
    Thoughts?
     
  2. Korkie

    Korkie Active Member SILVER Sponsor

    377
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    Either unit should cause the pump to turn on. Although I only have a single unit on my 340, that is how my neighbors is set up. It would appear you have an issue with the aft unit compressor not coming on. With the pump not coming on as well, sounds possibly power or thermostat related. Check to make sure there is power to the compressor when you turn on the system. No power, trace backwards to figure it out. There are also relays on the unit. Check to see all contacts are clean, especially if it worked fine last time/season. Cleaning contacts will become a regular maintenance thing, I usually do it during the off season as a PM thing. To check thermostats - if they are the same, swap them and see if problem moves to forward unit. Those are the simple things to check, beyond those is beyond me. I am sure someone on here will chime in with some other things you can check/try if the above check out.
     
  3. Blueone

    Blueone Well-Known Member SILVER Sponsor

    Jan 24, 2007
    Lake Erie, Ohio
    2004 420 Sundancer
    Cummins 6CTA 450's
    You should have a single pump that has a splitter right after the pump... One line going to each unit that passes thru the units and then to a discharge out the side of the boat. If your not seeing that discharge out the side then you have blockage in the line.
     
  4. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    This.

    Water should be flowing through BOTH thru-hull discharges whenever EITHER of the units are on. Besides a blockage, it is sometimes a strange air pocket. Filling backwards from the discharge with a hose can usually solve that.
     
    Blueone likes this.
  5. Robski97

    Robski97 Well-Known Member

    Jan 15, 2007
    North Bellmore, NY
    44DA
    Cummins QSC 8.3's
    each UNIT HAS A TRIGGER TO TURN ON THE PUMP. You have a bad trigger. Depending on the model and age u can get just the rigger or u might have to replace the board. U can google the brand of the unit and ac pump trigger as search words.

    Rob
     
  6. Blueone

    Blueone Well-Known Member SILVER Sponsor

    Jan 24, 2007
    Lake Erie, Ohio
    2004 420 Sundancer
    Cummins 6CTA 450's
    Your right if one thermostat turns on the unit it triggers the pump to turn on... but you will see the water exit the boat from both units even though the other unit is not on.... That's what he is saying he only sees one units water flow exit the boat...which would make you believe the other hose is clogged...
     
  7. Korkie

    Korkie Active Member SILVER Sponsor

    377
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    Or the clog is actually in the non working unit itself. That is where I found my clog 2 seasons ago. It appeared to be a hunk of Dirt. Take the hoses off the unit that it not working and hook them together with a piece of pipe n some clamps. This will help you find the location of the blockage. If you get water out of both exits, the blockage is in the unit. The unit can usually be cleaned out while in the boat. I did on mine 2 seasons ago using Barnacle Buster. Worked very well.
     
  8. TomA

    TomA New Member

    13
    May 24, 2018
    SeaRay 350 Sundancer, 1992,
    454 Mercruiser
    This is very helpful information. I suspected this was the case. Water is flowing nicely out of both thru hull openings, so there is no evidence of a clog in the line. Clearly the aft unit is not getting the info or trigger to turn on the pump. I will look into this first. Any suggestions as to what board to look at?
    So then my next question is - when the forward unit is turned on, and the pump IS activated, is that not feeding the aft unit?
     
  9. Korkie

    Korkie Active Member SILVER Sponsor

    377
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    Yes - when the pump is running, water is circulating thru both units. Not knowledgeable ref the board questions.
     
  10. markrsimon

    markrsimon New Member

    8
    Sep 1, 2018
    Cleveland, OH
    92 Sea Ray 400 Express
    454 Mercruiser
    As a suggestion - The unit that works, turn it completely off. This way your dealing with a single unit (the broken one).

    Make sure the broken unit has the fan set to auto. Turn that unit on (heat or cool) and several things should happen. The fan should turn on, the compressor should kick on, and finally the water pump will turn on.

    If the compressor kicks on, and the water pump does not - in a very short time the compressor will overheat and shutdown. Depending on the unit, you may get an error code relating to high temp or high pressure. If the unit does not shutdown, chances are the compressor doesnt work or isnt getting kicked on. If the compressor isnt getting kicked on then that probably explains why the water pump doesnt get kicked on either.

    Understanding where in the process things are failing will help with the diagnosis.

    Hope this helps.
     
  11. TomA

    TomA New Member

    13
    May 24, 2018
    SeaRay 350 Sundancer, 1992,
    454 Mercruiser
    Thanks for the advice.
    The water pump NEVER comes on when just the aft unit is turned on. The fan comes on, and the compressor runs (don't know if it's actually compressing, but it runs). My plan is to see if the trigger relay is replaceable. If so, I'm going to swap it with the trigger relay from the forward unit and see if that solves the problem with the water pump not coming on. That will address at least part of the problem. If the water pump comes on but the unit still doesn't heat or cool I will look into refrigerant levels first, then compressor. Make sense?
     
    Robski97 and Chris-380 like this.
  12. Korkie

    Korkie Active Member SILVER Sponsor

    377
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags, Bravo III Drives
    Sounds like you are right on target. :)
     

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