Refrigeration: Self-Contained or Ice Box Conversion ?

[osirissail]

I agree - but heh - I said it came from the $500/month thread group - whatcha expect? anyway here is a photo of the thing . . . .

[SV Demeter]

Yeah No thanks that thing is hideous and too small for my family to live out of.

I checked out the ozefridge and they seem like nice units but I am thinking a thin plate evaporator system is the way for me. Seems like better way to achieve more stable temps in the box.

Question now is whether to do two separate boxes and cooling systems connect the two boxes and use a spill over door or circulating fan to cool the fridge side.

Still thinking of about 7-8 cubic foot fridge and 1-2 cubic foot freezer. Now that R-parts is kaput where do I go for vacuum panels?

[osirissail]

Originally Posted by SV Escape Plan

Yeah No thanks that thing is hideous and too small for my family to live out of. . . . Now that R-parts is kaput where do I go for vacuum panels?

I also have a custom built 8 cu ft (4cu.ft. freezer and 4 cu.ft. refrig) and I designed it for Glacier Bay (California) vacuum panels. Supposedly they are the best as they are made from rigid fiberglass panels and have an R-50 rating for one inch. Also the information I had back then was that the soft mylar-type pouch-type panels did not hold the vacuum and quickly went to R-1.
- - So I built my box and designed where the corner notches needed to be for the holding plates and pipes. Then I made templates and sent them off to California and eventually got back a price estimate of US$6K for the panels and a lid (the lid was US$800 by itself). I bought the lid and frame, but passed on the vacuum panels.
- - I went back to my refrigeration books and determined that I could use "Home Depot" "R-Max Plus" foam board panels and achieve R-25 for the walls and more for the floors for a cost of about US$50. The R-Max boards are covered with silver foil which is even better. see: Roof Insulation Wall Insulation Polyiso Specialty Products | Rmax
- - I epoxied table top laminate sheets - kind of like formica - to the R-Max and use special silicon sealant to build the inside surfaces of the refrig/freezer.
- - I did install a drain (plastic thruhull for a dinghy) into the corner of the floor and lead a hose to the outside wall with another plastic dinghy transom screw plug. Now I can open the drain and use a garden hose to defrost and wash out the whole refrig/freezer in mere minutes.
- - I kept my original design concept so that if the R-Max boards did not work out I could remove them and slide in Glacier Bay Vacuum Panels (if I could ever come up with that much money).
- - Operation wise the calculations showed I would have to operate the refrigeration units for 1.5 hours more per day to make up for the loss in R-value between the vacuum panels and R-Max Plus sheets.

[SV Demeter]

Hey now this sounds like the way to go. Curious how you decided on the box sizes? I would not have thought to evenly split the freezer/reefer and would have thought 2 cubic feet of freezer plenty but 4 cubic feet of fridge too small? How do you like it? Do you live aboard and with how many crew? I had a feeling the vacuum panels would destroy my budget. But from reading Calders Refridgeration book (okay a little dated now) it seems like the lids the hardest part of the box to build so Im likin gyou r idea of buying the lid andf rame. I really want a side opening door too. I know they lose a lot of cool but I like to be able to clean the box easily and load easily. Would probably go with both a top and side lids for the fridge but top only for freezer.

Osiris how are you cooling the box? Do you have a divider and fans or spill over door? How many AH does your system consume in a day?

Thanks,

[osirissail]

On my boat I put the frig/freezer along the sidewall in the galley. There was a five foot long section available. I built up the area underneath the planned box with blue/pink insulation board until I could get a depth of 6 inches and then put a piece of plywood for the bottom inside of the frig/freezer.
- - I then went out and purchases the plastic bins that would be inside the frig/freezer and hold the foodstuffs. These I placed on the plywood and they set out the final dimensions of the inside of the frig/freezer. I wanted at least 5 to 6 inches of insulation boards between the box and the hull and no less than 3 inches in the front and sides.
- - Once the interior dimensions were set then I proceeded to built the layers of insulation boards and R-Max Plus to achieve the maximum R-value possible.
- - The top of the box thickness was set by the thickness of the Glacier Bay vacuum panel refrig hatch and frame.
- - I wanted redundancy in the box so purchased two CoolBlue 12VDC pallet style air cooled units - one set for freezer (5 deg. F) and the other set for the refrig at 35 deg F. Cold plates were then installed on ledges built into the box and the pipe routed to an area underneath the Force 10 Galley stove where I mounted the pallets. Because the hull was curved outward - as the box's vertical height grew I could build an offset ledge for the cold plates without interfering with the plastic bins that were to hold the foodstuffs inside of the unit.
- - I made a "false divider" wall out of R-Max Plus and kitchen laminate material that divided the freezer half of the box from the refrig half. The idea was that if one CoolBlue system failed I could remove the false wall and make one large refrigerator until the bad system could be fixed or replaced.
- - As it turned out when one system did fail all I had to do was hole drill some 2 inch vents between the freezer and refrig and I was able to keep the freezer section operating. There was no need for fans or other devices to circulate air as the cold plates extend the whole length of the outboard wall.
- - Over the years (10 so far) the unit has degraded somewhat and now needs half a day of running to keep things properly frozen/refrigerated. A lot of that has to do with how many times we open the box and remove things. AH draw for 8 cu ft is about 100 to 150 AH per day depending upon ambient temperatures and how often we open it to get a cold beer or soda or food.
- - The whole system was designed for KISS - that is single pallet air-cooled compressor/condensor and controls and one holding plate per box section. I only wish I had been able to get more insulation thickness in the front and top.
- - One major minus was I did not wrap the whole box in clear plastic sheeting between the actual internal box and the layers of insulation panels/boards. Kollman is adamant about preventing any water leakage to get into your insulation layers. Dropped cans and other sharp objects have put some fractures and holes in the bottom of the box over the years and I fear water has leaked into the layers of insulation.
- - After thoroughly researching all the online ideas and examples of how to build a boat refrig/freezer, it became apparent that any side opening door would be a major problem with keeping the cold inside the box. It makes sense as the freezer unit my mother keep in the garage is always a top loader/opening. The hours needed to keep the whole system proper would escalate dramatically if there was a side opening door.

[rourkeh]

I am going through the same refrigeration debate and have decided on the "Cool Blue" system Technautics Inc. Marine Holding-plate, Refrigeration, Boating, very low power consumption, very good reliability. I am using one box 42" x 18" x 30 deep and going 1/3 freezer 2/3 fridge. Have a look at there web site and testimonials. Not the cheapest system but well within your budget. Cheers

[SV Demeter]

Osiris, wow 100-150 AH per day for an 8 foot box, that sounds like a lot. My current set up is about that big with a horizontal evaporator and crappy insulation and on the worst 100* days here on the chesapeake Im still only pulling 70-80AH.

Cool Blue is interesting. I need to evaluate the holding plate vs thin plate evaporator topic I suppose. 24 AH in a day for an 8 foot box 2/3 x 1/3 sounds pretty good but I am always leery of these sort of statements.

The more I think about it the more i am leaning towards a single cooling system, two boxes, and either a spillover door or cooling fan to cool the fridge side.

I did some more measuring last night and I looks like I can within the existing footprint do 3" on the top, front, and sides, then 6" on the bottom. If I do more I will lose interior volume but that may be neccesary to get the R values where they need to be for fridge and that is my goal. Plenty of room where the freezer is going to get 6" all around. Now I need to research the insulation topic.

[SV Demeter]

Guess i need to do some more reading but what sort of R value should i be shooting for in the fridge side? I was thinking 30 for the freezer. What does the group think about this for insulation:

http://www.rmaxinc.com/downloads/Dat.../TSP-3.doc.pdf

[osirissail]

Insulation is the single biggest factor in cycling time and total AH usage. Second is how many times people open and close the lid letting in hot air. Third is how full you keep the box, empty boxes seem to take more AH to keep the temp where boxes full of food, etc. seem to take less.
- - The CoolBlue units I use actually draw 7 to 7.5 amps on my digital meter - each. So you can see if you are needing double the "run time" to keep the box cold there is a rather significant difference in AH per day.
- - For space for only 3 inches of insulation available I would suggest really researching thoroughly to get the max possible total R-Value. The bottom and outboard sides of the box need serious insulation because of the "heat sink" of the outside ocean/bay waters. What is around the outsides of the box can make a significant difference especially if there are heat generating equipment next to the planned box. The more time you spend "thinking" things out and considering all the parameters and possibilities of the box, the happier you will be when the whole thing is finished.
- - The link above to R-Max board is what I think used to be called R-Max Plus board. I used 4 inches for the R-26.4 value on the front and sides. Anyway, that is the stuff I was talking about earlier. Just be sure to install some kind of water barrier between the boards and the actual box in case a seam leaks.

[daddle]

Originally Posted by SV Escape Plan

...What does the group think about this for insulation:

http://www.rmaxinc.com/downloads/Dat.../TSP-3.doc.pdf

The 'group' has some odd ideas. I think PolyIso foam is a second choice. As I stressed repeatedly in another recent thread some of these foams are hydrophyllic - they absorb water. The R-Value heads for zero. That's why there is foil on the surface.

Look for Extruded Polystyrene. Blue boards made by DOW. Completely hydrophobic. No absorption. Build with staggered and tight joints.

I've used PolyIso for a boat fridge. But each piece and the whole thing was wrapped and taped tightly with stout polyethylene sheet to keep the moisture out. I was in a hurry and couldn't find PS board.

[osirissail]

I looked up Dow's polystyrene blue board and got a tech sheet that said "As previously stated, expanded polystyrene is not a suitable insulation for moist environment. " And also that the R-value was 3.84 per inch which is lot less than R-Max's R-5.9 value per inch. Here is the link: Dow Product Summary
- - I do know they changed the color from blue to pink some years back. I used the blue board to insulate the inside walls of my boat completely around the above water parts of the hull. It was much cheaper than R-Max and more flexible.

[daddle]

I should have stressed Extruded Polystyrene. Expanded is the coffee cup junk.

From your link:

Styrofoam Square Edge (extruded) - This product is often called "blueboard" due to its light blue color. In spite of its relatively modest "R" value (4.92 per inch), Styrofoam SM is our overwhelming recommendation for foam ice box insulation in marine applications.

[osirissail]

Yeah -I thought you were talking about something else as I used the old blue board stuff on my boat and it was smooth and definitely not the coffee cup stuff. Speaking of which that white or whatever color, big "granular" boards that causes the little white pieces to fly everywhere when broken - is a big No, No on a boat. The large granular structure allows mold and algae to permeate into the material and grow. However, the "extruded" stuff is totally different and does not have any problems - except - that the R-value is still 20-25% below R-Max for the same thickness.
- - So it would roughly take 5 inches of blue board to equal 4 inches of R-Max. Where space is a major limiting factor finding the highest possible R-factor is the target measured against the cost of the material. That is, $5000 worth of vacuum panels is not as cost effective as $50 worth of R-Max. Unless, you do not have any choice due to space constraints. I even made the passage way smaller in the area by the new refrig/freenzer so I could get another inch or two of insulation around the box.

[daddle]

Seal that R-Max in polyethylene or in a year you'll just have a R-1 wet sponge.

[billyehh]

I approached refrigeration from a different angle. My catamaran had a front opening fridge and a chest freezer both around 7 cu ft. It was powered by two Cold Machines going to cold plates. It only had shore power which was rarely used and 130 amp alternators on each anchor. M cruising area is the Eastern Carribean around 12 degrees north.

After the first season of running the engines many hours a day I had enough. First to go was the front opening fridge. It frosted up so badly that the holding plate had to be defrosted almost twice a week. It took forever to freeze the holding plates and the freezer really just barely kept things frozen.

The second season I installed 4 130 watt solar panels and a Blue Sky controller. The panels were installed flat above the bimini and with about 4 ft. between each pair to avoid being shaded by the boom. On sunny days it starts producing power at about 0630 and reaches 30 amps by 1000. At about 1430 it slowly decreases until 1800 hours. Mind you this is on sunny days whichis the norm.

I tore out both holding plates and turned the front opening fridge into storage which I needed. The top opening freezer was turned into a fridge by replacing the holding plate with an L shaped evaporator about 32 inches long fed by the existing air cooled compressor. The result was i only had to run engines twice during the season to charge the batteries. This meant I had a fridge only but no freezer.

The third season I added a small Engle portable freezer under the chart table. It is barely 1 cu ft. but is amazing how much meat you can get into it. Again the solar panels did the lions share of charging. Over night I was down between 70 and 130 amps depending on howmany movies I watched. This kept me in the upper 25% of capacity of my battery bank of 600 amps. By the way the batteries are AGM's and are 9 years old this season.

This year I am putting an exhaust fan in the compressor locker to help cool and improve efficency. It only draws 0.4 amps so I should get some energy savings. I am also lookingat recomissioning the Spectra 8 gallons per hour watermaker.

I agree that the most important thing you can do is insulate the box. All that is for naught if you have a front opening box. If possible I would consider a longer shallow box rather then front opening. It is not as effiecent as a deep box but beats the heck out a front opening one.

It used to standard to run watercooled systems in the tropics, but the newer 12 volt air cooled compressors seem to be Ok on their own. Good ventlation is a must.

I am lucky that I have so much acerage above my bimini to make this system work. Your plan with 480 watts of panels plus a wind generator should give you lots of power for both a top loading fridge and a freezer.