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Old 23-07-2010, 08:27   #31
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Thanks a lot guys all very good info here. A few thoguhts:

1. Insualtion, I wonder if I laminate the R-max panels with fiberglass cloth (vacuum bagged) thus encapsulating them from moisture? I cant afford the vacuum panels for the whole box but was going to use them for the lid as that seems to be the hardest part to build. I have 3" of crappy insulation now and will most likely go to 4 but want to maximize the R-value per nominal thickness. I get the moisture concern. When you all say seal the R-max stuff in Polyethylene what exactly do you mean? Wrap it in plastic sheeting and tape the seams? Why not just get 4" thick R-max and vacuum bag it with fiberglass cloth? Maybe the epoxy will react with the foam and dissolve it? Still wondering what is an ideal R-value for the fridge. I read that R-30 is where you want to be on a freezer so im at 26 or so with 4" of the R-max foam on the sides and 6" on the bottom of the fridge I should be in good shape right? Use 6" all around on the freezer.

2. Osirisail: 7-7.5 amps is the reason I am not interested in holding plate systems, that and the irregular temps. My air cooled grunert unit I have now is pulling 5.5 at start up and one cooled its around 4.5 -5 amps. No way can I support 14-15 amps, especially if it needs to run half of the day so 12 hours , thats like 170AH in a day. I would like to keep the demand around 70-80ah and would hope for 50-60.

3. The side door. I am considering using one in addition to top loading but the side door would only be used to load and clean the box not day to day access. Although this means likely another vacuum panel so maybe we'll bag the whole idea. I just hate the friggen contortionist moves needed to clean the box and having to pull a bunch of crap out to get to the stuff I want. Sure better loading and organization would help but I'm sure we have all be where Im talking about.

4. Separate boxes. I think I am just about ready to rule out that option as I dont want two systems to worry about. That would mean I either have to find space for 2 compressors and the related equipment, plus deal with the AH loads of running 2 units, or use a self contained unit like the Engle, but still have the dual AH loads. Curious though billyehh what does your Engle draw?

I ordered Kollmanns 12/24 volt book and have read Calders older book on refrigeration. Any other book reccommendations for box construction? My plan is to use a combination of foam, glass, marine plywood, vacuum panels for the lid(s).
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Old 23-07-2010, 08:49   #32
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I am still using my Engel 35. It may be to small for your needs but it is IMHO as bullet proof piece of equipment as there is. Mine has been running 24/7 for over 3yrs at a draw of 2.7A. If I turn it way down I can freeze a gallon jug of water hard as a brick overnight even when the fridge is trapped in my sealed up cabin at about 90F.

I'm not sure about ugly but in my twisted perception 1 moving part keeping my beer cold for 3years without so much as a hiccup is a thing of beauty.

Of course I can't hear all the noise an AirX makes either. Odd huh...........m
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Old 23-07-2010, 09:57   #33
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Three things are on my mind regarding fridge/freezers:

1. Can I get more value by reducing the cold losses and learning to be smarter about what needs to be stored in the cold?

I'm looking at an older vessel that has 12V cooling. It draws more amperage but is in very good condition. I'm actively researching replacing the insulation with some top shelf stuff, hoping to keep the heat transfer minimal.

Heat transfer works both ways, though. Adding lots of hot items will raise the internal temperatures as much as an insulation leak. In the past I had a deep fridge and kept several gallon containers of water stored in the bottom. The water acted as a cold source and if the added mass was small compared to what was already in the fridge, the temperature rise was slower than filling the fridge with warm objects.

From my research I've learned that a lot of items don't need to be kept refrigerated, and that many others last far longer by being kept chilled. And while there's no denying that a cold beverage can be a fine reward for hard work, I wonder if a cool one isn't as good. So, I'm working on a list of priority items that I consider necessary for cold storage.

Better insulation leads me to not want a front loading fridge since the cold loss is far more than a top loading unit. While it can be quite convenient to open a door and look in, again I'm not sure I want to pay the energy cost. I'm learning that by carefully loading and arranging the contents of the fridge, I can get to most everything with little effort.

By keeping the fridge lightly loaded, the cold air is allowed to circulate better, reducing cold and hot spots and allowing the system to be more efficient.

2. Can I live with a smaller box and do I need a freezer?

I'm under the impression (and possibly wrong) that a freezer is the biggest draw of cold power despite the thicker insulation. I've learned from hard experience that loading the freezer can lead to expensive problems when it fails. Ice and ice cream are a real luxury and I'm not sure I want to pay the price.

It seems to me that the higher the temperature difference, the greater the flow of temperature. A freezer at 5F and the ambient temp of 90F has a higher temperature difference than a fridge temp of 40F and the same 90F ambient. In this case, the freezer difference is about twice the fridge and since I don't have twice the insulation, there is the chance of more cold loss.

I do want to keep items that don't seem to have a long shelf life in the freezer. Those tend to include meats, veggies, and caught fish. These items seem to taste better than their canned competition. By having a freezer I can keep the food costs more in line with my budget and have treats when the fresh produce is long gone (I have a slow boat).

3. Can I keep the energy costs reasonable?

Insulation, smarter positioning, and understanding what is best to be kept cold seem cheaper than a bigger compressor, more batteries, or more power generation. Having used engine driven compressors, and very much liking how fast these pulled the cold plates down, I'm still heading for a 12V system. I can leave it alone and go away for a day or two and not worry about these valuable items thawing or spoiling.

I'm also wondering if adding a bigger cold plate would allow the system to keep contents cool before having to start. The downside, I think, is that the compressor will have to run longer in order to bring the larger plate down to temperature.

One thing I did learn was to have the fridge/freezer running when I added new, and sometimes warmer, items to the units. This way, the system has a good chance of getting the contents cold, suck out as much heat as possible, and slow down the cooling time. Where I normally ran the engine for an hour/day twice a day to keep the system cold, I'd run the engine for a couple hours or a couple of cycles when adding lots of warmer items to the system.

As interesting the idea of using the fresh water tankage as cooling for the chiller system is, I'm very leery of this due to the potential of catastrophic water loss or contamination. I wonder if I might prolong the heat exchanger by scheduled flushing of the system with fresh water and a salt removing solution.

I'm thinking that for the cost of a bigger/newer/more efficient cooling system I'd get a better ROI by improving the insulation, making sure the compressor system was running as efficiently as possible, keeping the items stored in the cooling system to the necessary items, and accessing the system as little as possible. I'm also becoming a convert to canning. This simple, inexpensive, and well proven technique for preserving food items requires little energy (usually propane) and keep for long periods of time with no energy preservation requirements.

From my research, the fridge/freezer system is in the top 3 energy draw systems. Perhaps it's time to look at either modifying my cold requirements, actively preserve fresh items for long periods with low energy requirements, or use this expensive, but not necessary, system in a better way.
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Old 23-07-2010, 12:42   #34
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For my family refrigeration is not a luxury but a neccessity for live aboad comfort. I know lots of folks who live a cruise without it and thats fine, just not for me.
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Old 23-07-2010, 15:44   #35
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I know there are many who will disagree with me, but I don't feel you get that big a penalty with a front-opening fridge. The energy required to cool air is not that high. I did some calculations and to cool 8 cubic feet from 40C to 0C would be very roughly .3Ah. Round it up and call it an amp every time you open the door. Compare with removing half the contents of the top loader to get to the beer at the bottom, then picking it all up when the boat rolls and it's probably a wash.

My wife, who had a top loader on her old boat and suffers a top loader on our Catalina, will not allow me to put one on the new boat. My plan is to compromise and build a fiberglass or acrylic drawer for the fridge, top loader for the smaller and less used freezer. My hope is that the drawer will allow front loading with less air exchange.

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Old 24-07-2010, 08:38   #36
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When I wrapped my PolyIso (R-Max like?) panels I used moderately heavy polyethylene (like a heavy zip-lock bag might be made of...or more). Wrapped them like a gift package and fully taped with the best packaging tape. This was after making sure each panel fit perfectly because any little gap really hurts the end result. The tiny gaps, like a millimeter or two, were filled with spray in foam (which is a terrible insulator but better than a gap).

A friend has a front loading fridge in a big cat. If he's not down on his knees trying to find something he's down on his knees chasing things around the galley floor. One could mount it higher and solve the first problem while exacerbating the second. Great idea unless you plan on leaving the marina. Maybe if the door and interior were both proper bins, and not plain shelves, it would work.
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Old 24-07-2010, 09:02   #37
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Originally Posted by mikereed100 View Post
I know there are many who will disagree with me, but I don't feel you get that big a penalty with a front-opening fridge. The energy required to cool air is not that high. I did some calculations and to cool 8 cubic feet from 40C to 0C would be very roughly .3Ah. Round it up and call it an amp every time you open the door. Compare with removing half the contents of the top loader to get to the beer at the bottom, then picking it all up when the boat rolls and it's probably a wash.

My wife, who had a top loader on her old boat and suffers a top loader on our Catalina, will not allow me to put one on the new boat. My plan is to compromise and build a fiberglass or acrylic drawer for the fridge, top loader for the smaller and less used freezer. My hope is that the drawer will allow front loading with less air exchange.

Mike
I agree with the top vs front argument. It is the stuff you put in that needs cooling down that takes the energy not cooling the air since it doesn't hold a lot of BTUs. I thought that was becoming kind of "conventional wisdom" among the refer set?

Jim
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Old 24-07-2010, 09:17   #38
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Originally Posted by daddle View Post
A friend has a front loading fridge in a big cat. If he's not down on his knees trying to find something he's down on his knees chasing things around the galley floor. One could mount it higher and solve the first problem while exacerbating the second. Great idea unless you plan on leaving the marina. Maybe if the door and interior were both proper bins, and not plain shelves, it would work.
Absolutely. I had a front loader on my Catalina for a while but as you point out, it could not be opened at sea or anchor. Plus, when it would defrost all the water would end up on the carpet. That is why I plan a drawer type front loader. No door, just a large drawer with compartments to keep things from rattling around. The drawer will be longer than wide and could be fitted with acrylic lids over the compartments to help keep the cold in while open.

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Old 26-07-2010, 13:14   #39
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The front opening door if used would only be used for cleaning and occasional loading but at this stage its less of a priority in the project.

Im still struggling with whether to do two separate units, fridge and freezer or one combined with a spill over door between the two. Im also still looking at vacuum bagging the insulation panels with fiberglass to encapsualte instead of wrapping in plastic but am not sure how that will work in practice. Need to find out if the foam will react with the resin or not.

Right now Im leaning towards 4" of foam vacuum bagged in fiberglass for the fridge and 6" for the freezer. Will probably buy a custom lid from a vacuum panel maker and hope to get 6" of foam on the bottom of the fridge. Expect the fridge will be somewhere about 7 cubic feet maybe a touch smaller and the freezer 1.5-2 cubic feet. Was hoping to use a frigoboat system with a keel cooler and BD50 compressor and a thin plate evaporator bent around 3 sides of the freezer with the 4 side having a spillover door to the fridge. Unit would be for use in the tropics. I will have an 800 AH bank of 6volt AGMs with a 100amp Balmar alternator and smart regulator for charging. Also plan tohave 480watts of solar that will hopefully run the fridge/freezer while we are away from the boat. I have a second alternator on the engine that I am going to set up to charge the starting battery and serve as a back up alternator but it I believe is only about a 50 amp unit.
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Old 26-07-2010, 13:53   #40
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If you haven't done so already, you might check out Calder's Boatowner's Electrical and Mechanical Manual. The chapter on refrigeration is full of good stuff and more up to date than his refrigeration book.

Mike
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Old 26-07-2010, 15:41   #41
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So how about the best of both worlds?
I have a thin evap/ air cooled unit that I salvaged from a dorm style refrigerator (about $80) I paid a refrigeration guy $100 to vac it down and add refrigerant after I did all the plumbing. This set-up works great dockside or when the genny is making 120V. I have a bunch of Gel-Ice packs, which can be picked up at any shipping supplier cheap. They work like a holding plate in that when there is power they chill down then absorb heat when there is none..... Also,they store many more BTU's than water ice without the mess.

My ice box is stock from the manufacturer and will hold 60# of ice + food for about 8 days before anything starts getting (too) warm. 20# of ice gel does the same thing. I have very limited battery storage and have found that I need about 4 hours a day of Genny time to maintain refrigeration, lights, and fans. I run 2 hours in the morning and 2 hours in the evening before turning in.

I have plans to build an arch for 2 solar panels and a wind genny (as well as dingy davits) in the next year or so before I cruise full time. Right now, I only get 14 day trips in every other month, so the fossil fuel generator works for now.
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Old 26-07-2010, 16:31   #42
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I have seen in the boat suppliers the systems with the thin evaporator plate as a very long "plate" which you can bend into a curve at the corners of a box - sort of wrap around versus the old pre-made smaller units.
- - For long distance cruising, I like having redundancy which means two refrigeration units for one box with a separator wall which can be removed if one unit fails. I also consider the freezer/frig a necessity of life and am not into eating canned beans and veggies for months on time. So I want a "back-up" system should the main system fail. That is why I liked the single pallet 12VDC air-cooled units versus the engine driven or keel cooled or water cooled or any of the older designed systems. They may be more efficient but if they fail what is the back-up?
- - A cold plate is merely a container of water with the cooling tubes in it. The water freezes and acts like that old-fashioned block of ice. I believe in the tech books including Kollman's he prefers holding plates. It has been a decade since I built mine.
- - The problem with the front opening door is the "seals" and frame of the door which uses two continuous frame of plastic from the inside to the outside and a rubber foam seal. My top lifting vacuum panel hatch seals are already totally shot.
- - My new suggestion which I want to use when I rebuild my system - is to make a fiberglass internal box sized to fit the pre-selected storage bins/containers for food. This continuous box - except for an opening on the top side for the access hatch and a hole in the bottom for the drain - and - holes for the refrigeration pipes - would have no seams anywhere. Sort of like a holding tank but made of thin skin fiberglass with a gelcoated interior. It could be made my taking a wooden mock-up mold of the internal shape of the box and laying the fiberglass cloth/resin to make the bottom and sides. Then gel-coat it. Then make a flat fiberglass panel with the hole for the hatch. Then install the evaporator and/or cold plates and seal the pipes. Then fiberglass the top to the box. This whole box would then drop down into position with the "R-Max" or whatever surrounding it.
- - I hope what you referred to as "foam" is the flat sheets of R-Max or something similar and not liquid two part expanding foam or the "can" stuff. The two part liquid foam is not uniform in density so has a horrible R-value. The "can" stuff shrinks and disappears with age and heat.
- - I mocked up the whole assembly with sheets to the maximum possible considering hull shape and used liquid expandable foam only to fill the voids outside the laid up sheets caused by the curve of the hull. This was primarily for support purposes for the flat sheets and not for insulation purposes.
- - I heard somewhere that Glacier Bay (Calif) got out of the marine refrig business, I don't know - - -but they had a 12VDC air cooled system that was much more efficient than the "CoolBlue" Technautics units that I bought. I was at a SSCA convention (GAM) and the Technautics guy was giving "half off" for the show so I couldn't resist and bought everything thing from them.
P.S. The whole process was a very thought and labor intensive project but since I consider it a major priority system in a cruising boat, it is definitely worth all the time researching and brain-energy necessary to make it the best you can devise and construct. I have encountered cruisers with a "bad" refrig/freezer set-up and they are definitely not happy campers.
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Old 27-07-2010, 11:43   #43
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Have read all of Calders stuff and am reading Kollmanns book now. Thanks all.
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