Grunert Refrigeration Issuue

Sep 24, 2017
31
Hunter 380 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,
 
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Likes: fireman331
Jun 6, 2006
6,990
currently boatless wishing 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
 
Sep 24, 2017
31
Hunter 380 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
 
Aug 17, 2010
208
Hunter 410 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!
 
Feb 14, 2014
7,399
Hunter 430 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...
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
Does the unit allow you to measure the plate temp? How is it adjusted in terms of target temps.
 
Sep 24, 2017
31
Hunter 380 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
 
Sep 11, 2011
390
Hunter 41AC Bayfield WI, 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.
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 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).
 
Sep 24, 2017
31
Hunter 380 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.
 
Sep 24, 2017
31
Hunter 380 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.
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
looks great and right now it is working and I have frost on the plates and everything is cold.
Then you compressor is fine.:clap:
Can you measure or catch a sample to measure discharge water temperature?
Jim...
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
NOAA has your water temperatures around 53°F. So your Cooling water temperatures should be a lot higher. Guessing 60°+
Jim...
 

SG

.
Feb 11, 2017
1,670
J/Boat J/160 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
 
Aug 17, 2010
208
Hunter 410 Dover NH
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.
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.
 

viper

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Jul 31, 2016
131
Hunter 380 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
 
Aug 3, 2015
26
Hunter 380 San Diego
Hi Tucson Sailor.... I live in Phoenix but also have a Hunter 380. It's a 2000. I keep her at Sun Road marina in San Diego. My Grunert system stopped cooling. The pump was still running although the water was barely circulating, as the flow outside the boat had slowed to a trickle. So I called a local marine company that diagnosed a thru-hull that was not allowing sufficient water into the pump. I had to have the boat hauled, and the thru-hull replaced. But the problem was solved. The unit is back to performing beautifully. You might start with your diver to see if he can find an obstruction at that thru-hull. It's at the bottom of the steps, and the thru-hull is next to the the engine water intake. If you don't see diminished flow outside the boat, this is probably not the issue. Good luck.
 
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