Author Topic: Fridge Option Questions?  (Read 89 times)

Richard

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Fridge Option Questions?
« on: April 26, 2019, 04:31:43 pm »
I am working on the refrigeration options in my Gulfstar 51 Sailboat-- the current setup has two separate boxes for fridge and freezer- each has two holding plates approx 16 inches x 14 inches and 3 inches thick. The system is an older Crosby unit which is 110 volt water cooled- it still works fine but we are planning on going cruising next year in the Caribbean and think we would prefer 12 volt as we have 400 wind genny and almost a kilowatt of solar power to charge batteries. Dimensions of the two boxes are as follows
fridge- 46" length x 22" width and 28 inches deep (one holding plate on each end (22" walls)
Freezer- 21" length x 15" width and 21" deep (one holding plate on each side)

both have a seperate thermostat- there is also a separate ice maker installed but i am not overly concerned with it. I believe it is a separate system with its own internal compressor etc.
In your opinion what is the best option?
1)leave the old system in place and add in a Technautics system on the blank walls of each of the boxes
2) tear out the old system completely and replace?
3) tie into the existing system by adding a 12 volt component ( not sure this is feasible)?
4) take out everything but the holding plates and reuse them?
5) something else that makes more sense to someone with more expertise than i have
Thanks in advance for informed opinions!
     
ANSWER
Usually 46 foot and larger sailboats are equipped with onboard generators and industrial type refrigeration not 12 volt refrigeration. These large sailboats almost always have on board air conditioning to prevent mildew by dehumidifying interior air and to provide creature comfort in hot weather conditions. The Gulfstar 51 regardless of the model will be equipped much the same as other boats of this size. Because these boats have accommodations for eight or more people this is why refrigerator box is so large in this boat, 16.4 cubic feet. The freezer  is 3.8 cu ft. The two refrigerator holding plates are sized for only a ten cu ft box which means compressor most run more than twice a day. The freezer plates are sized correctly for a box of five cu ft.

The main concern with refrigeration in boats especially older boats is the insulations  resistance to conduct unwanted heat. Even closed cell insulation over time can outgas the insulating gas stored in each cell allowing moist air to inter these cells. There are ways to determine if insulation is still expectable for the cooling energy available.

This boat currently has an operating refrigeration system that can answer the open question about is there enough insulation or is more refrigeration capacity requires. By reporting present compressor current draw and hours of compressor running time in a 24 hour day and adjusted for any changes in planed cruising climate temperatures, many questions can be answered.

Additional questions asked by owner:

In your opinion what is the best option?
1)leave the old system in place and add in a technautics system on the blank walls of each of the boxes?
My answer-- Yes, your boats single refrigeration system does need redundancy for a year cruising in the Caribbean. An Cold Eh Marine designed system especially designed by John without wasting space of an additional eutectic plate is a good 12 volt solution for freezer. The 16 cu ft refrigerator boxs heat load in the tropics or even in Texas is too large for any of the small 12 volt refrigeration units. Grunert refrigeration has HP 12 volt units that would solve your problem for the refrigerator cooling capacity. John at Cold Eh Marine also has a twin 12 volt Danfoss condensing unit that could supplement the old Crosby and also provide redundancy.   

2) tear out the old system completely and replace?
My answerWhen I do a worst case projection of Btu of cooling required in the tropics for both boxes you need 11,280 Btu of cooling per day. It would be difficult to remove present system and find a equal or better system that is presently designed for your application.

3) tie into the existing system by adding a 12 volt component ( not sure this is feasible)?
My answer I would need to see a picture of existing holding plates. Crosby 30 years ago used Dole eutectic plates with duel evaporator coils inside. This design of a plate makes it possible to connect another condensing unit to all plates without disturbing present system.

4) take out everything but the holding plates and reuse them?
MY answerYes it is possible but I an not in favor of it unless plates are reconditions correctly and new condensing units refrigerant flow corresponds to plates evaporator coil size insuring adequate oil return to compressor.