The Worst pleasure boat refrigeration.

[pbmaise]

My water cooled Danfoss has been a pain for two reasons. The water cooling has clogged with shells?, and the condensor was mounted under the sink where it got corrosion from water from spray hose.

I would much rather go inverter air cooled using AC system.

[Richard Kollmann]

If you followed this complete thread there are no pleasure boat refrigeration unit reported as the worst. There were a number of products that were not so good and others that were unfriendly like water cooled condensers on small 12/24 volt systems. There is always going to be an application best suited for each refrigeration unit manufactured. Companies that experimented in the past with not so good refrigeration ideas have now shutdown or diversified to other than refrigeration products.

Noticeable after reviewing this long boat refrigeration thread that pleasure boat refrigeration has different meanings to the different types of boaters. The majority of boaters only want a single temperature box used primarily as a drink cooler, others want a colder single temperature zone refrigerator box. Most any insulated box with any type large enough evaporator sizes to satisfy a single 36 degree F temperature zone box is except-able. When a boater wants to use refrigeration for more than day trips and wants more than a single temperature box the evaporator selection always should comes before selecting refrigeration condensing unit. Four cubic foot boxes can have a freezer section with the right evaporator. For any freezer evaporator compartment to be affective over more than a two weeks period the evaporator needs to surround all product in freezer section.

When a energy storing plate is used in single temperature freezer section it is best that frozen meats be in contact with plate or there are two energy plates directly opposing each other with product in the middle. To insure product in freezer remains frozen enough to maintain best taste of food it is recommended that cold air be allowed to move down and around frozen product. Wooden rail running down the side of freezer across the bottom and up the other side will provide the path for natural air tumbling necessary for colder air to descend and warm air to rise.

Spillover refrigeration has been used for as many years as ice boxes by put the heat absorbing ice or refrigerator evaporator in the top of a box where cold air descends and warm air rises to be captured by the colder ice or evaporator. Spillover refrigeration in pleasure boat refrigeration is much the same induction air cooling but when it comes to top loading boxes and vertical wall evaporators heat flow is horizontal near top of box and cold air also moving in the other direction lower in box. Natural induction horizontally air movement was never the best so today we use conventional thermostat controlled fans to regulate cold freezer air into refrigerator. On larger boxes with small 12/24 volt refrigerator and freezer boxes are side by side two totally independently compressor systems are the best solution.

It seams like the old idea of keeping it Simple, Reliable, Energy efficient without daily monitoring has given away to unnecessary troublesome gadgets generated by creative marketing. When told you need water cooling on a small refrigeration system means the design of system you are looking at is not designed for application installation in your boat. Boat refrigeration marketing companies in the US no longer are showing an interest in conventional water cooled or even eutectic plates in small boat refrigeration systems.

[Cheechako]

-The old Norcold units put in powerboats often were terrible, they were just super unreliable. No idea why. A joke really.
-I did not find a tinkers damn bit of difference in two units I had that had water cooling and fan cooling.. temp or power usage. Turn the pump off you never knew the difference.
-In the 70's the hip thing became using a 1/2 HP DC motor to belt drive a quality compressor. Hah! What a waste, power hog comes to mind.
-In my 47 footer I had a huge fridge freezer ? 8-9 cu ft?? (with the above noted 1/2 hp belt drive) I also had a ~ 2 cu ft refrig in the middle of the salon table. I decided to insulate the little one with those metal vacuum panels. It was a PITA to do. I found it not better, from a "time to run the engine to charge" standpoint than no vacuum panels. You still had to run as long to keep it cold.

[Uncle Bob]

Originally Posted by a64pilot

I can explain why Richard keeps referencing a Eutetic system as one that is best used when there are alternative systems available, often Solar.
It’s because the other name for a Eutetic system, is HOLD OVER system, the tanks are a large thermal mass and the original designs for these systems were to take a whole lot of energy out of a large thermal mass (the tanks) and by using the properties of a Eutetic fluid being able to absorb a large amount of heat when they melt to “hold over” for a day or so, then when there was excess power available whether from running an engine or the middle of the Solar day when your batteries are in absorption, you take that excess power and freeze those plates back down.

You have a system that is capable of storing excess power when it’s available, assumption of course is that excess power is available at some time of the day.

However many eutectic systems aren’t really Eutetic systems anymore, meaning that the fluid never phase changes, so while they have “hold over” plates, they aren’t being used that way. Doesn’t really matter so long as it works and is energy efficient.

If you don’t use the energy storage of a “hold over” plate, then there in no technical advantage to the things, as was stated then they just take up more space in the box.

From a pure thermodynamics point of view it’s more efficient to remove heat from a mass with a thin plate evaporator as it’s doing so directly, a hold over plate, you remove heat from the fluid, and the fluid removes heat from the food and that is slightly less efficient than removing heat from the mass directly.

Now so far as this or that test that “proves” a Eutetic system is more energy efficient than a thin plate evaporator, the test is flawed, unless the operating conditions are the same, and I’m not talking box size, temp or insulation etc.
I’m talking system design, if one system requires the compressor to operate at a much lower COP due to its evaporator being undersized or at least smaller than the other system that is allowed to operate at a much higher COP, then of course the system that is operating at the higher COP will be more efficient and use less power, cause COP means coefficient of performance.

The difference however is not due to being Eutetic or thin plate, it’s the system is operating at a higher COP, due to the design differences between the two “identical” systems, in other words they are not identical.

But at the end of the day whether Eutetic or thin plate, the system that uses the least amount of energy will be the system that is properly designed, with properly matching components, that allows the compressor to operate at an efficient COP.

Took the liberty of researching the test that Ozepete did and I believe that the thin plate was in fact larger at 400x400 than the holdover tank at 400x300, would that make the holdover tank or the thin plate more efficient?

[Richard Kollmann]

Originally Posted by Uncle Bob

Took the liberty of researching the test that Ozepete did and I believe that the thin plate was in fact larger at 400x400 than the holdover tank at 400x300, would that make the holdover tank or the thin plate more efficient?

Uncle Bob, Any one who understands the heat movement through different metals, water, and ice would need to question this analysis. This test had two major flaws. The energy consumed and excessive compressor cycling during standard evaporator test was a result of having to remove heat from the eutectic plate left in the box. Technicians intentionally use water containers and cold packs in boxes to store more energy, and yes it does require compressor to run longer.
The second flaw in this test comparison was when eutectic plate was used as a cycling plate the standard test between two different evaporators is by comparing actual K value rating of each,one at a time under the same conditions. There are simple formulas to find refrigerator evaporator K values on the web if you want a true comparison of eutectic
versus Rollbond evaporators.

Another problem with this comparison for day or weekend boaters is the slow response in freezing eutectic solution at warm start up when using a capillary tube as all other system manufactures use rapid response Thermo Expansion Valves and refrigerant Receiver.

[waterman46]

It is clear that when a yacht is equipped with a reliable inboard generator and has difficulty finding good mounting places for more than a couple hundred watts of solar, then eutectic holding plates are a better solution than evaporator plates since basically you are using the holding plate as an energy storage (actually heat sink) location to avoid battery usage. And holding plate systems avoid the efficiency losses of compressor start-up which is constantly happening in the simple evaporator system. Far as I can tell, the only advantage of the simple evaporator for boats not running quite large solar and wind installations, is that it just costs less. And it's just as good as any holding plate system, while at the dock.

As for water cooling vs air cooling, consider the heat capacity of water vs air. You better be blowing one H of a lot of air over a large radiator to equal what a small water pump and heat exchanger can handle. And it is simple to locate the sea water heat exchanger very close to the compressor output. An air radiator along with it's duct and clearance requirements is much larger and would have to be in a location where it's heat can be dumped outside the boat, so that must limit your choice of location. Many boats have enough thru-hulls for other purposes that it is no big deal to tee off one of them to get your cooling water for the refrigeration. Ours is teed off a 2" cockpit drain thru-hull.

If air cooling is so good, then why don't we air-cool our diesel engines? Is there any reason why air cooling is more desireable than water cooling for smaller heat loads while less desireable than water cooling for large heat loads?

Perhaps on catamarans, more room can be found for the larger volume required to house air coolers and certainly there is more room for solar panels as compared to monohulls. So on the cat, really the advantage goes to constant cycling systems.

[waterman46]

Originally Posted by a64pilot

From a pure thermodynamics point of view it’s more efficient to remove heat from a mass with a thin plate evaporator as it’s doing so directly, a hold over plate, you remove heat from the fluid, and the fluid removes heat from the food and that is slightly less efficient than removing heat from the mass directly.

I think I would take exception to this statement. In theory there can be no efficiency difference simply caused by use of holding plates vs evaporator plates. What happens is that it just takes more time for the same heat to be removed from the food in the holding plate system.

During holding plate cool-down, yes the energy of the compressor is being used to cool the eutectic fluid first, then later that fluid absorbs heat from the food. But after the compressor shuts off, now you have a long time period of no energy usage by the compressor yet the food is still giving up heat to the eutectic solution. So its just a matter of delay of cooling of food in the holding plate system.

After a complete cycle, there is no difference in total sum efficiency due to solely whether you used holding plates or evaporator plates. Any efficiency differences would be caused by how well matched the compressor is to the evaporator/holding plate, possibly lower efficiency of a smaller compressor used in a evaporator vs. the larger compressor for a holding plate system and the fact that energy is lost each time the compressor has to start up.

[GILow]

Waterman46, thank you for bringing some cold (pun intended) hard logic to the discussion. There are too many sweeping, unsubstantiated statements being made that demonstrate, to my mind, a lack of understanding of the basic physics involved.

Now I concede I don’t know enough about the subtle end of refrigeration to make any statement about the relative efficiencies of either system, but I do know enough to spot the obviously flawed statements such as the one you noted.

Thankfully I don’t lose any sleep over the relative efficiencies of either system because my Ozefridge works so efficiently that I barely need to consider the power consumption. It may well be that there is a system out there that would have used less power, but I’d be amazed if the difference was more than a few AH each day.

[RaymondR]

It's wrong because putting a warm mass into an insulated box which includes a large heat sink will result in a faster heat transfer than putting it into an insulated box from which the heat is being withdrawn comparatively slowly by a heat pump.

[Pete7]

Originally Posted by waterman46

And holding plate systems avoid the efficiency losses of compressor start-up which is constantly happening in the simple evaporator system.

Is it a problem though? our air cooled evaporator fridge runs for about 2 minutes every 10, so 6 start ups an hour. this drops to 4 start ups during the evening and night.

Originally Posted by waterman46

Far as I can tell, the only advantage of the simple evaporator for boats not running quite large solar and wind installations, is that it just costs less. And it's just as good as any holding plate system, while at the dock.

Our evaporator works just as well at the dock with shorepower or at anchor. Be pressed to notice the difference.

Originally Posted by waterman46

As for water cooling vs air cooling, consider the heat capacity of water vs air. You better be blowing one H of a lot of air over a large radiator to equal what a small water pump and heat exchanger can handle

I think this depends on location surely? PNW or European NW, air cooling is fine. Our compressor unit is located under a work top with a large area of GRP hull including below the waterline. Since the hot air rises cooler air must be drawn from the hull area below the waterline. The hot air is either cooled as it drops down inside hull or escapes behind the cabinets through the boat.

Originally Posted by waterman46

And it is simple to locate the sea water heat exchanger very close to the compressor output. An air radiator along with it's duct and clearance requirements is much larger and would have to be in a location where it's heat can be dumped outside the boat, so that must limit your choice of location. Many boats have enough thru-hulls for other purposes that it is no big deal to tee off one of them to get your cooling water for the refrigeration. Ours is teed off a 2" cockpit drain thru-hull.

The air cooled evaporator kits are even easier to install. Bolt down, and screw together two copper pipes, add power and it works. Ducting and vents, not needed.

I agree water cooling is super efficient at extracting heat having spent decades freezing my butt off doing decompression diving. The idea of putting a water cooling unit in the water tank is easy enough and warrants consideration if the Isotherm air evaporator fridge kit ever fails. However, it's 12 years old now and still functions perfectly, so we have had our monies worth out of it.

Would a hold town kit work better? Not sure, but we lack the ability for fast large power generation. Indeed being 50N we are set up to use the long daylight hours during the summer to meet our energy needs as we go, rather than banking energy in batteries or cold plates to use later. Should we ever head south of the Med which is unlikely, this may need re-thinking, but then so will lots of other stuff.

Pete

[RaymondR]

Because the small city I use to do my off-cruising-season maintenance is on a river away from the coast and it is summer in Australia the heat in the boat gets is stifling in the heat of the day period.

I have two 12 Volt auto radiator fans mounted in plywood which fit into the main hatches to pump outside air into the boat and a number of small circulation fans I can use to circulate it.

Provided I lie about and read during the hottest part of the day I can get by without aircon which I'm not a big fan of anyway.

The fridge condensing unit is under the sink in the galley and whilst I know intellectually that the small amount of heat pumped out by the air cooled condenser should not result in an appreciable increase in temperature it feels like the galley is at least 3-4 degrees C greater than the rest of the boat.

Oh for a water cooled condensor.

[nilespf]

For me it is all about duty cycle.



For comparison can we get the cubic ft of the freezer, if you can keep ice cream frozen - not soft during normal usage, current draw to run the system and finally duty cycle after temps have reached stabilized temperatures. How often the reefer is accessed will impact the data but with some luck it will be during evening hours after the parties.



We have covered every conceivable method to effect all kinds of efficiencies but I still can't answer the fundamental question "is a eutectic system going to yield a reefer system that will yield a DC significantly lower than my current system".



The best I can get out of my evap coil system is 48% DC with an average draw of about 5A. Fridge (5 cf) cycles spill fan at 34 to 39 degrees and another controller keeps the freezer 4.6 cf between 0 and 26 deg. Short of rebuilding the box I think it's as good as it gets.


Cheers--hope some folks have additional info.

PN

[waterman46]

Originally Posted by nilespf

For me it is all about duty cycle.



For comparison can we get the cubic ft of the freezer, if you can keep ice cream frozen - not soft during normal usage, current draw to run the system and finally duty cycle after temps have reached stabilized temperatures. How often the reefer is accessed will impact the data but with some luck it will be during evening hours after the parties.



We have covered every conceivable method to effect all kinds of efficiencies but I still can't answer the fundamental question "is a eutectic system going to yield a reefer system that will yield a DC significantly lower than my current system".



The best I can get out of my evap coil system is 48% DC with an average draw of about 5A. Fridge (5 cf) cycles spill fan at 34 to 39 degrees and another controller keeps the freezer 4.6 cf between 0 and 26 deg. Short of rebuilding the box I think it's as good as it gets.


Cheers--hope some folks have additional info.

PN

It really isn't all about duty cycle. It's about how well matched the compressor is to the evaporator. Whichever type is in use. There is a method of adjusting the metering of the refrigerant into the evaporator at the expansion valve. Properly tuned and with a compressor matched to the requirements, the same amount of energy must be used by the compressor regardless of evaporator type, to keep the box contents at a given temperature.



So it is possible to have an inefficient system with either type of evaporator or even a low duty cycle.


You didn't specify the ambient temperature in your own experience. Makes absolutely huge difference. Some on this thread are in quite cool climates and I would not use their data. Raise ambient day/night sea and air average temperture to 82F or higher and we have a different story.

If I understand your average current to be 5A, then you are using 120AH per day. Your freezer is rather large, 4.5cf, and if you are meeting your criterion of keeping ice cream hard, and if you are in a warm area I'd say your system is about the same efficiency as ours was (before it died after 16 years of service). It required about 50AH for the freezer and 50AH for the larger refrigerator.

Keeping ice cream hard requires 0deg F inside the box. Our holding plates varied from -15F to -5F. Actual box contents were about 10deg warmer. But actually cruising in the tropics renders moot the question of hard ice cream. Once you are in the tropics, it is impossible to bring ice cream from the market back to your boat. It will turn into soup before the dinghy ride is over!

[nilespf]

[QUOTE=waterman46;3086806]It really isn't all about duty cycle.....


Thanks for the reply Waterman,
If I understand your point we agree there are many relevant items that affect the running DC of our systems. My hope is to compare using as few figure of merits as possible. I understand that DC will wander all over the place for any number of reasons. My fear is I'm operating way out on the bell curve indicating any number of possible problems. You have brought up a good point that GPS location should be considered.

The eutectic system sounds great but I don't know if a properly designed evap system will yield the same energy usage. If they both are the same then I still can consider the flywheel cooling effect during the night and put a price on that. If I have enough batteries to withstand evening drainage then it may become an issue of do I want to tear the boat apart to insulate the box (assuming the box is the problem). Currently I can get through the night only because I have 230 Ah of capacity.

Pn

[Richard Kollmann]

[QUOTE=nilespf;3086994]

Originally Posted by waterman46

It really isn't all about duty cycle.....


Thanks for the reply Waterman,
If I understand your point we agree there are many relevant items that affect the running DC of our systems. My hope is to compare using as few figure of merits as possible. I understand that DC will wander all over the place for any number of reasons. My fear is I'm operating way out on the bell curve indicating any number of possible problems. You have brought up a good point that GPS location should be considered.

The eutectic system sounds great but I don't know if a properly designed evap system will yield the same energy usage. If they both are the same then I still can consider the flywheel cooling effect during the night and put a price on that. If I have enough batteries to withstand evening drainage then it may become an issue of do I want to tear the boat apart to insulate the box (assuming the box is the problem). Currently I can get through the night only because I have 230 Ah of capacity.

Pn

An important fact to remember is all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor. No other component of refrigeration system creates energy especially a thin plate or eutectic plate evaporator. This means all energy provided to refrigerator's compressor comes from an electrical power source. The most energy efficient place to store energy for 12 volt refrigeration is in batteries. Neither the batteries or a eutectic plate can create energy. The best way to create and store energy is from an alternator or battery charging from alternative energy Solar, Wind and others secures of electrical power.

The old days of blaming excessive energy use do to compressor cycling no longer is true with variable speed high COP compressors.

It seams like Fake News is now a way of life these days