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Old 20-07-2010, 14:10   #1
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Refrigeration: Self-Contained or Ice Box Conversion ?

I have already posted this over on Kollmanns board but figured I would ask here as well:



I want to replace our current refrigeration/freezer system with one that will be better suited for our needs. Below I will try to list the constraints and our needs. I am considering all options at this point so standalone self contained units I are an option so are 2 comletely separate units.

43' Ketch, liveaboard cruising, 2 adults, 2 kids, tropics, very little to zero time plugged into shore power,800 ah house battery bank consisting of 6volt agms (this may be able to expanded to 1k AH), would like to be able to leave boat and have wind and solar meet energy needs. Initially thinking 300 watt wind unit and (4)120 watt PV.

Not sure how big of a fridge and freezer but am thinking I want to stay with a 12v dc system and not use an engine driven holdover plate. Was thinking I would build a new box where the existing one is and use a combination of foam and vacuum panels for insulation to balance $$ and space requirements with need for effeciency. Was thinking I would build a separate freezer unit and use a spill over door to cool the fridge side, but maybe just two separate units all together. Was also thinking a top loading freezer but side loading fridge as top loading fridges are a pain to load, clean, find stuff etc.

I was considering a frigoboat system with a keel cooler to provide the cooling but I am open minded and want to design something that is robust, effecient, and as big as possible given the desire to meet the robust and efficient requirements.

Would a selfcontained unit like a norcold be a good option? Maybe separate freezer and fridge units? How well are these insulated and how effecient are they in the tropics?

This is a big project but given that this equipment is the most energy hungry system on the boat I want to do it right. Thinking my budget here will be $5-8K.


Thanks,

Ted Reshetiloff
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Old 20-07-2010, 14:28   #2
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The holding plate and engine-driven compressor will be by far the best from point of view of your energy budget, but you seem to have already rejected that so I'll say no more.

You seem to have decided on a normal conventional system and I think there's nothing wrong with that as long as you've got the means to put in enough power every day to keep it running. Two separate boxes with separate compressor is the luxury solution which will allow you to store frozen food (huge benefit) and regulate each box individually, but it will consume double or even more than double the power of a single box. But, you know, you can do the math and decide for yourself whether your energy budget can handle it. That's what we have and I wouldn't change it. The separate freezer is so great. But we we have heavy-duty generator, heavy-duty alternators, and lots of diesel tankage -- got the picture? Cooling luxury doesn't come cheap, energy-wise.

I don't think there are huge differences in efficiency between the various modern compressor types. We use Isotherm SP, which use special through-hulls (used for cockpit drains) with condensor coils built into them. SP means "self-pumping" -- the water oscillates through the through hull creating natural circulation. Works great.

The Frigoboat is also supposed to be pretty good, but the conventional keel cooler type condensor means more holes in the boat, and is not supposed to be quite as efficent, as the Isotherm.

I would personally go with either Frigoboat or Isotherm which in my opinion are better than the conventional type which circulates sea water through the condensor. You've got a pump to run (feed with power, replace when it breaks) and you've got sea water flowing around in hoses which can break. No thanks.

I heard somewhere that there's something new out which has a holding plate and a very smart controller which will suck down lots of power and freeze the plate when it senses that there is abundant power, and will hold off and not consume power beyond absolute minimum required, when it senses that you are on batteries. Maybe someone here has heard about that in more detail; I don't know. Sounds very interesting.
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Old 20-07-2010, 14:35   #3
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Ted,

I think you need to do the energy math to really get a handle on this project. The size of the battery bank is not important since you want to recharge the battery bank to as close to 100% when it reaches 50%. This is optimal lifespan for those batteries. Adding more batteries won't help what so ever. You need to look at your charging ability being increased not the size of the bank. You bank you have sounds pretty good and the bulk of your power will be for the fridge / freezer. The dual system approach for a family makes sense but this does not really work like you use in a home so your usage patterns come into play. For max efficiency you need max insulation. For dedicated freezer it's hard to imagine too much. Again you don't want the largest possible sized fridge / freezer because the energy load will be important. You want the smallest fridge / freezer that will serve you so you can add the most insulation and use the least amount of power. It's the way that works best.

Compute the maximum charging ability you can install for solar first. You just won't find many anchorages in the shade so that will be a good number and investment. They don't break down often. A wind generator can do well in 15 to 20 knots but who wants to anchor in a place like that? A wind gen is great on a passage when you are sailing. The idea is if you can't recharge it don't install more batteries! You have to pay back the batteries regularly and more of them just takes longer. I would compute batteries based on a 24 hour period where you draw down to 50% then get back to 90% or so since the last 10% takes a long time. AGM's do absorb faster but require tight regulation else you will trash them quickly. Your 8K budget needs to include the charging gear. That costs more than the fridge. The big ticket is power usage. With a water maker you can add even more. A water maker is almost a fridge as far as power. Use patterns govern here as well. Long showers gets to be very costly.

Look at the power budget and match it to the fridge capacity to get the best overall system.
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Old 20-07-2010, 15:26   #4
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Paul;

Taking the batteries down to 50% ?? I thought running in the upper 25% range was optimal for long life... I read on here somewhere that 50% was a killer for battery life, cutting a 10 yr lifetime down to something like 2-3. Is that the same for his type of batteries?
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Old 20-07-2010, 15:57   #5
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Thanks Guys. Lots more to ponder here but the charging budget is a separate project. Currently the charging system includes a 120amp alternator and a 6kw genset that I am hoping to not run too often. The reason for not wanting an engine driven holding plate system is I want to be able to leave the boat for a few days have the system take care of itself. Maybe that means shutting down the fridge and just supporting the freezer? My comment about wanting the biggest box possible was in the context of available energy contraints. Good thought on the wind genny and calm anchorages I had not thoguth about that point. I am hoping to achieve pretty high R values for the both boxes. Maybe a better question is what is a reasonable assumption for Amphours produced from (4) 120 watt panels in a given day in the tropics, yeah I know, "it depends.."
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Old 20-07-2010, 21:14   #6
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Quote:
Originally Posted by cdennyb View Post
Paul; Taking the batteries down to 50% ?? I thought running in the upper 25% range was optimal for long life... I read on here somewhere that 50% was a killer for battery life, cutting a 10 yr lifetime down to something like 2-3. Is that the same for his type of batteries?
If you look at the battery manufacturers battery cycle life graphs you will see that it is a curve, not a straight line. The deeper the discharge the less "cycles" you get out of the battery. Battery life is now regarded as the number of discharge/charge cycles rather than fixed months/years. From the graphs you will see you get more cycles (life) with less than 50% discharge before recharging. But it is a curve with the optimum life being between 25% and 50%. More than 50% discharge before charging shows a real decrease in cycle life. And recharging with less than 25% discharge gets a little excessive as you are forever cycling the charger. So the happy medium is somewhere between those two numbers and it really more personal preference than anything else, kind of like the what anchor to use debates.
- - Different battery technologies/types/chemistry each have their own cycle life charts, so the %'s change.
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Old 21-07-2010, 02:18   #7
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Here is that refrigeration system I was thinking about:

Marine Systems

They call it a "hybrid" system because it has a euctetic holding plate. The system senses when there is abundant power (engine running, genset running, wind generator spooled up well, shore power, etc.) and will use the extra power to freeze the plate.

The idea is fantastic, I think. It means that power will be used to freeze the plate which would otherwise be wasted, which means using less power when you're "coasting" on batteries. It should help a lot with your power budget.

However, I have heard a number of negative things about the maker, Glacier Bay, so you should proceed with caution.

If you decide to research this, and you in fact find out more about it, please do share with us.
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Old 21-07-2010, 04:12   #8
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Escape Plan, I am in the middle of doing exactly what you are contemplating, I am about to order an ozefridge system www.ozefridge.com.au the package 5 with twin tanks, and adding the The ECO-2 optimizer, it is a power management unit that reduces battery demand by operating as follows: (copied from their site)

1.) Whenever power supply is abundant (Mode A), the ECO-2 automatically triggers the system's controller into run mode starting the Ozefridge system, forcing it to consume, convert and store the abundant electrical energy into the eutectic plate(s) as thermal energy for future use.
2.) When engaged ECO-2 also operates the Ozefridge system at maximum compressor speed to convert the most refrigeration into eutectic storage while the power supply is abundant.
3.) When ECO-2 takes control the eutectic mass is maintained in a frozen state within the lower half of the pre-set temperature operating range to maintain the most eutectic thermal mass into storage while the power supply is abundant.
4.) During normal operations the ECO-2 checks constantly for the availability of abundant power. This ensures that any abundant power is always detected.
5.) Whenever only limited power (Mode L) is available, the frozen eutectic mass will hold-over the cabinet temperature for up to a day or so and if no further opportunity to use abundant power occurs in the meantime, the system automatically reverts to using the limited battery supply as further refrigeration is required.

this is the same type of system $3850 + extras as Dockhead is describing in his post, the quote for my system was $2130 AUD or $1870 US, in their testimonials there are some people from the states who have bought these, may save you some dollars to put towards solar/wind. so far they have been great to deal with. Hope this helps!!
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Old 21-07-2010, 04:38   #9
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A tip: Whatever you do try to use generic refrigeration parts wherever possible. Refer troubles are common in cruising. Vibration, salt, heat: it's a tough job. But generic parts are widely available. Fancy custom ones, not. Make sure you have a standard fill port and a sightglass where you can see it.
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Old 21-07-2010, 06:25   #10
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We have the Frigoboat system and we love it.
We went to the Miami boatshow and all the refrigeration experts there told us that the modern evaporator systems are so efficient, that they use the same amount of power in a day as the holding plate systems. The advantage of the evaporator is that you have a constant temperature in the fridge all the time. So there's never a question if the frozen chicken defrosted and refroze.
With the Frigoboat system you get a digital thermostat, which is awesome. You can see what the temp is without having to open the door. It also has a smart speed control that changes the speed of the compressor with the amount of power you have available.
We initially bought the aircooled unit, as we are on a steel boat. But we have since added the keelcooler. It's fantastic. The other systems with the coil in a thru-hull is IMHO not the way to go. We met a guy in a boatyard who had that system and the coil was covered in barnacles after only a few months in the water. He had a heck of a time trying to get the barnacles off. The Frigoboat is flat, much better.
Our friend also has the Frigoboat with keelcooler. He regularly leaves his boat on anchor for a week, and when he comes back the batteries are still full and the fridge is cold.
We love our system and would recommend it.
Good luck.
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Old 21-07-2010, 06:46   #11
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We did this and agonized over this as we cruised with a great Glacier Bay holding plate system with D/C compressor that was a miser on energy and wanted to do the same thing. Unfortunately Glacier Bay doesn't make that system anymore the one on their website was not being made last summer so they weren't selling them.
I ended up going with a Sea Frost unit for both freezer and refer that was air cooled (much against my basic instincts but on the advice of many) and love it. They really do as well as they are estimated. I have been using it during this heat wave with 100 degree temps and getting usage as good as was calculated or better every day. The interesting thing was the calculation for water cooled vs air cooled was not much different for my use and the air cooled are certainly easier to install and maintain without the through hulls and pumps.
I kept hearing about modern compressors being so much better then they were when I last cruised that the energy from the water pump becomes more of a concern but just didn't believe the folks that were touting them but I have to say I am now convinced through my own testing and they really are an alternative to water cooled even in the summer.
Your mileage may vary but it is worth talking to Cleave at Sea Frost before buying. I am glad I did.

Jim
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Old 21-07-2010, 07:00   #12
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KISS!!!!

When we bought our boat 16 years ago, it had an adler-barbour air-cooled refrigerator with a spill-over system. It had a box evaporator which kept the meat inside it frozen, and the surrounding box stayed at 30-40 degrees. The spill over box was more like 45 degrees. I thought that upgrading this system would be one of our priorities, but I got busywith other things and decided to wait till the admiral complained or the system had a breakdown.

After 16 years, mostly in the tropics, the Adler-Barbour finally died last month (it had been on the boat 10 years before we bought it). I just replaced it with an identical system (well, they don't use R-12 freon any more, so its almost identical).

One of the reasons I didn't go with a more sophisticated system is that I have spent the last 15 years watching my friends deal with refrigeration problems. For example, I spent a week on a boat in Israel, where the refrigeration 'expert' came back for the FIFTH time to fix a system which had two air-cooled compressors, one for a freezer and one for a refrigerator. He had already replaced both compressors, driers, one evaporator, and the lines, and his bill was over $3000 and the system still didn't freeze, even though the compressors ran continuously. I have also seen the engine driven systems have seal failures, and line failures, cooling water blockages and pump failures. Our air-cooled system runs just fine on the hard, and according to PS, is more efficient than the AB water-cooled system until the air temperature exceeds 104 degrees.

One of the reasons that my system ran so long was that it never was near salt water, and only had two moving parts--the compressor and the fan.

As far as energy usage, maybe I can't keep ice cream, but with 230 watts of solar power and a wind generator, I end up running the engine for an hour about 1 day out of 4, and most times that is to move anchorages or heat water for showers. I would think that 480 watts of solar would be more than enough--on average I get 75% of my power from the panels, but the wind generator comes in handy on windy and cloudy days (beware the advertising gimmicks on wind generators--swept area is the key to power generation, not misleading graphs).

We also keep the boat loads down--I'm typing away on a netbook, which only draws 1 amp, we have converted most of our lighting to LED, and we watch our movies on a portable DVD player instead of the big TV.
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Old 21-07-2010, 08:05   #13
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Lots of good info here folks. Last night I did some measuring and it looks like the current box is about 6.8 cubic feet. It has a horizontal evaporator in it now and is in general a lousy box but I would like to end up with the fridge being close to this size, say 7 cubic feet, but with better insulation. Im thinking the frezzer would be nice to be about 1 cubic foot and will either be a totally separate system or will be connected to the fridge box and use a spillover door to cool. The fridge will have bot top and front loading doors and in practice we will try to minimize the use of the front door. I am still leaning toward this type of set up as opposed to two separate compressors and evaporator systems. I am also still leaning towards a Frigoboat style system with the keel cooler, although I would like the ability to use the system when on the hard so maybe an aircooled option? Im not worried about the need for another through hull as I have a few extras left over from the OEM head systems which had direct discharge capabilities that I have since done away with.

I still have the question of how much energy (either watt hours or amp hours) should I expect in a give 24hours from (4) 120 watt solar panels?
And of course how many amp hours will the above referenced refer system consume?

Thanks again to all who have responded.
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Old 21-07-2010, 09:08   #14
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Energy usage is probably the largest consideration in refrig/freezer's installations. Insulation plays a major part of that equation.
- - I have a reservation about engine driven refrig/freezer installations as running the main diesel "unloaded" for several hours every day or so is not IMHO a good thing. The air-cooled total unit on a steel tray system are sometimes less efficient but considerably more serviceable and replaceable. Even amongst the air-cooled "single pallet" units there can be quite a difference in advertised power usage.
- - Of new interest is the units from the "$500/month" thread - Compare Engel 12-Volt Fridge Freezer Technical Information
Everything is solved as far as insulation, etc., with only the challenge of finding a place to put it and a way to provide the necessary airflow to the compressor/condensor part of the box.
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Old 21-07-2010, 09:34   #15
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Man those things are hideous! Maybe efficient but ugly as hell. They dont look very large either. Even the 84 quart model is only 2.8 cubic feet. Am I missing something here?
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