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Grunert Refrigeration Issuue

Discussion in 'Big Boats' started by Tucsonsailor, Dec 30, 2017. Add this thread to a FAQ

  1. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    Hi:

    I have an issue with my Grunnert water cooled refrigeration unit that I have not been able to solve and I am hoping the community might have some suggestions.
    Had my refrigeration guy come out and evacuate my unit and recharge it. Unit has been running for 5 days straight. It shut off last night and the refrigeration temp went up to 50 degrees. Then it started again and is starting to get cold. It seems as if the compressor has a mind of it's own and I can't control a temperature level. Also, I am not used to having a water cooled unit, usually it has been air cooled, but are the water cooled units supposed to be pumping water all the time. I have had several of my fellow boaters come up to me and ask me if my boat is sinking because it looks as if a bilge pump is one, however it really is my water pump to my compressor unit. I have a Danfoss compressor that looks in great shape, however, I do have one thermostat unit in the freezer that is suspect. How do I determine whether my problem is a thermostat and not something greater? This is on a 380 Hunter with a freezer and a spillover system on the other box. Any suggestions would be appreciated.

    Thanks,
     


    fireman331 likes this.
  2. Bill Roosa

    Bill Roosa

    Joined Jun 6, 2006
    6,965 posts, 140 likes
    Hunter 40.5
    US Harrington Harbor North, MD
    The water pump should only run when the compressor is running. If the pump does not run it will eventually set an "overheat" code on the unit and shut it down. The unit will also not cool much at all with out the pump running. since you have water flowing I'm not thinking that it is the pump however. Sounds more like an air leak in the freezer/reefer box or thermo problem to me. Check the seals on the doors by using a dollar bill. Shut the door on with the bill inserted between the door and seal. It should not pull freely out. The door latches may have shifted and are not compressing the seals resulting in an air leak.
    good luck
     


  3. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    Hi Bill
    Appreciate the advice
    Is there anyway to know if the thermostats are Affecting this?
    I do t mind replacing them but would like to make pretty sure that’s the issue
    Btw seals seam real good

    Thanks
    Jay
     


  4. scottdube

    scottdube

    Joined Aug 17, 2010
    175 posts, 11 likes
    Hunter 410
    US Dover NH
    Hi Tucson,

    Not sure I agree with Bill on this. I had a similar refrigerator unit on my 410. It had water cooling which could be on or off. It was more efficient to have the water cooling on when the outside air temp was high. Is the freezer box getting down to temp? If it is and the compressor keeps running I would say the thermostat is bad, if it is not getting down to temp you have something else going on. Are the cold plates getting covered in frost? If you need a new thermostat I would get a hold of Cleave at seafrost.com. They have really good stuff. I replaced my grunert stuff with their systems last year and love it!
     


  5. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,760 posts, 757 likes
    Hunter 430
    US Waveland, MS
    If you have a way to measure the temperature of the discharge cooling water it could tell you a lot about your unit operation.

    I have a laser Temp probe and can measure the temps of the inlet and exit water at the Evaporator coil. The difference in temperatures will give you much info on compressor operations.

    Example: sea water 20°C -- Discharge water 30°C when compressor first starts. [good]
    after 4 hours of compressor running...
    Sea Water 20°C -- Discharge water 25°C then something is happening but not thermostat.o_O
    Jim...
     


  6. SG

    SG

    Joined Feb 11, 2017
    989 posts, 156 likes
    J/Boat J/160
    US Annapolis
    Does the unit allow you to measure the plate temp? How is it adjusted in terms of target temps.
     


  7. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    Hi
    When running my plate temps are 15-20 sometimes lower
    The box works great then however it shuts down for no apparent reason. And doesn’t turn back on again until everthing is melted
    Very disconcerting
     


  8. ice breaker

    ice breaker

    Joined Sep 11, 2011
    224 posts, 25 likes
    Hunter 41
    US lake superior
    I purchased a cheap indoor outdoor digital gage when I was trying to diagnose my freezer problem. The outdoor sensor is on a wire that can be hung in the middle of the freezer, so you can watch the temp change without opening the door. It also will capture the high and the low as the thermostat cycles. Most freezers will get as low as -8F on their coldest continuous running setting.

    From what you have said I see a potential problem with the thermostat, but also a potential charge issue. If you needed to have the system evacuated and recharged, because it was not cooling properly, and the tech could not find and repair the leak, the system has not been repaired. The new gas will leak out too. Your plates at only 15-20F seems much too high if the compressor is running continuously. These small systems typically have only about 2 -4 oz of refrigerant in them. Small changes in charge can have significant impacts on the performance.
     


  9. SG

    SG

    Joined Feb 11, 2017
    989 posts, 156 likes
    J/Boat J/160
    US Annapolis
    I would be more interested in the plate temp and what is happening with it than the box temp. That reacts more slowly and will be less informative.

    You should be able to adjust the target shutof and when it once again runs on.

    You should see the temp start to drop as the compressor runs.

    You don’t have to let the plate thaw. You can cool it down periodically by cycling it (?ubless you aren’t on the boat).
     


  10. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    Hi:

    I have heard good things about SeaFrost however, not sure how bad my Grunert systems is. It looks great and right now it is working and I have frost on the plates and everything is cold. I am just not sure how to control it. It can stop at any time.
    Not looking forward to spending $2500 on a new system.
     


  11. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    That's good information. I appreciate it. I am looking for a new refrigeration guy, but they are hard to find in the Bay area. Two of the good ones just retired and we are a little light on that kind of talent up here.
     


  12. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,760 posts, 757 likes
    Hunter 430
    US Waveland, MS
    Then you compressor is fine.:clap:
    Can you measure or catch a sample to measure discharge water temperature?
    Jim...
     


  13. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,760 posts, 757 likes
    Hunter 430
    US Waveland, MS
    NOAA has your water temperatures around 53°F. So your Cooling water temperatures should be a lot higher. Guessing 60°+
    Jim...
     


  14. SG

    SG

    Joined Feb 11, 2017
    989 posts, 156 likes
    J/Boat J/160
    US Annapolis
    Do you have a manual for your system and it’s controls? You need to watch what happens when the plate reaches its set pint; and see that the plate temp drops while getting to that point.

    If you are not aware, you shouldn’t be adding refrigerant just add it. You can cause problems with too much refrigerant
     


  15. scottdube

    scottdube

    Joined Aug 17, 2010
    175 posts, 11 likes
    Hunter 410
    US Dover NH
    Sorry I wasn't clear I meant to say call seafrost about a using one of their thermostats. His stuff is superior. I replaced my grunert thermostat with another crappy grunert thermostat and it was still hard to control.
     


  16. Tucsonsailor

    Tucsonsailor

    Joined Sep 24, 2017
    28 posts, 3 likes
    Hunter 380
    US Alameda
    Thanks
    I will give him a call
     


    scottdube likes this.
  17. viper

    viper

    Joined Jul 31, 2016
    128 posts, 14 likes
    Hunter 380
    US Cape Coral, Fl
    I have the same H380 with the same water cooled unit.
    The small .5-1 amp water pump has been a problem for me. The warm water along the SE coast promotes growth in the line and it gets clogged/burns out the electric pump. Replaced pump, worked great again for a couple of days. I constantly clean filter and back flush the lines. The motor does not pump water fast enough to prevent growth in the line in the summer.

    I have never had my unit shut down, when no water was pumping even in the hottest of conditions, however the cooling does degrade to the point ice cream will not stay frozen. I have had the pump cut off for several months now.

    When in port, with the A/C running, cabin temps below 80, no problems...

    In 2001 Hunter went to the air cooled compressor. Likely for the reasons I cited. Water cooled more efficient (when working), but its a pain. Also the water cooled pump operates off the starter bat.

    I will replace this year the water cooled with the air cooled version... yep, 700 bucks....

    Otherwise I'm quit happy with my Freezer Fridge spill over system... Not quit as easy to access as front door fridge on my larger boats in the past... but adequate and stays very cold.. Heck put some ice under the rack in the fridge and it will stay cool for a week even if the Freezer is barely working.

    Regards,

    Viper