The Worst pleasure boat refrigeration.

[Uncle Bob]

Originally Posted by Pete7

I had to google it, but you have a similar climate to us. I must measure our fridge sometime (Isotherm GE80 kit), but it's about 2cu ft, say 55 litres. During an average summers day I see the fridge using 3A when running for perhaps 2-3 mins every 10, less during the night. So the fridge uses about 20 - 25A a day.

The portable 20 litre freezer uses a similar amount (3A) but runs much longer 4 mins in every 6 mins, despite only being opened a couple of times a day and has a bath towel over it.

Pete

Pete, I have a 40 litre portable that I only use as a freezer and I have found that the travel cover supplied with it made a small improvement in power consumption, then I bought a 10 mm thick high density foam camping mattress roll and cut it into panels that fit snugly inside the travel cover, leaving all vents open of course, it's a bit of a squeeze but works well. Reduced power consumption and run time duration.

[Uncle Bob]

Originally Posted by Richard Kollmann

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.

Richard, I couldn't find the original test results so reached out to Ozefridge for clarification. Here is part of the response regarding the order of the test.
The original thread with the test data (now removed from CF!!!) clearly indicated that the tests were done in sequence starting with the EUTECTIC system first, and therefore the cyclic system period benefited from the hold-over from the eutectic plate period.
This would seem to indicate to me that if either system had an advantage it was indeed the plate not the eutectic. Surely if the plate needed more power to keep the box at the existing temp that it was at the start of the test the results are clear.
As to your other points, yes the fridge needs to be switched on prior to use, preferably the day or evening before and as to you describing the system as a cycling plate, not a eutectic system, just pray tell what is the practical difference. It cools down to a predetermined point, switches off and switches back on when the temp rises to another predetermined point, keeping the box and it's contents within the selected temperature range.
The published results have apparently been mimicked by a number of happy customers who have put their hands up and said so, along with some that I have met on their boats who are also very happy.
Please, no more snow to confuse the issue, I just cannot understand your many and varied objections to this published test. I have no intention of participating in a rerun of the original bun fight so I guess I will leave it here.
Cheers.

[a64pilot]

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?

If you look I’m that thread at some point Pete stated there the thin plate he had, had the compressor operating at a lower COP due to it having to be colder than the cold plate in order to maintain the same box temps.
Now some of that may be due to the operating principle of a thin plate, that is it’s only cold when the compressor is running and a cold plate remains cold as that’s it’s purpose.
However I took it to mean that if the thin plate had a larger surface area, then it could operate at higher temps, and higher temps mean a higher COP for the compressor.
If your curious, Danfoss publishes the COP vs temp in a table for each of their compressors.

Then just as a comparison if you look at an Engle, a portable of course, but it’s a thin plate evaporator, but the evaporator wraps around the interior of the entire box, only way it could get more surface area if it also was on the floor and lid.

The whole point of my post was to try to say that there is nothing about a cold plate that makes one more efficient than a thin plate, that in fact a thin plate can be just as if not more efficient, if properly designed in a matched system.

Now just to make things clear, I have a cold plate system, a dual cold plate, that I am very happy with, but I do understand that it’s possible to design a thin plate system that could be as efficient, but I went with the system I did for it’s simplistic design, ease of service and reputation, not because it had cold plates.

However any conversion fridge manufacturer meaning one that manufacturers a system meant to be put into an ice box to convert it to a vapor cycle refrigeration system, can’t control the most import part that more than anything determines the efficiency, and that of course is the insulation of the box itself, I believe to a large extent that’s why some are very pleased with their systems, while someone else may have the same system and be very displeased, because their insulation sux.

But to get back to the test, any test comparing two different types of evaporators, In order to be a “fair” test, all the operating conditions need to be the same, to include the COP the compressor operates at.
If the COP is different, then of course the one with the higher COP will be more efficient, that is what COP measures.

Now that may be difficult to do, to match components like that as many of course pick components based on price and availability as well as other considerations, like will it fit in the box etc.
Manufacturers of almost anything don’t actually manufacturer everything of course, most is bought off the shelf and they cherry pick components to make a system.
If you have ever “built” your own computer it’s a lot like that, your really an assembler not an actual manufacturer.

[a64pilot]

For those that want to “improve” their system, buy an AEO module.
It really reduced my electrical consumption, and it’s probably wishful thinking but I swear it now cools down faster as well, but I admit that’s probably the placebo effect

My system is a 14 cu ft spillover, roughly half and half, it has a BD80 compressor to try to cool that huge box, the compressor by use of the resistor in the thermostat wiring had the compressor running at max RPM, but it has a thermal expansion valve that based on temp of the evaporator will regulate refrigerant flow, so it mechanically controls refrigerant flow, and therefore the load on the compressor, so even though the RPM is fixed, the load and amp draw would vary with how much the TXV was open.

Enter the new AEO Danfoss module, based on the last cycle it will vary compressor speed, meaning that if it doesn’t have run at max RPM, it won’t, it will only run at the speed necessary. It can’t look ahead if you will, it only knows what to do this cycle based upon the last cycle, but really and honestly when everything in the box is fully cold and I haven’t added a lot of food to it, the compressor system will slow down and only draw 4 or 5 amps, and that’s quite low for a 14 cu ft box and a BD80 compressor, the compressor is also running much cooler, just a little warm to the touch.

Slowing it down is much more efficient than leaving it at max RPM and throttling it with a TXV.
I prefer a TXV over a fixed orifice though, but back to if perfectly designed, nothing wrong with a fixed orifice, it’s just tough to be perfectly designed as a manufacturer if you can’t control box size and insulation.

Take your old module and put it in spares, you need a spare one anyway, as they are hard to get out cruising, and I believe compared to the other components, they have a high failure rate.

The AEO is also a soft start, if you watch your amp meter, you can watch it ramp up RPM, it doesn’t start wide open like the old module.
Also at least mine has no detectable RF, my old one to use the SSB I had to turn it off, it was incredibly noisy, the new one I can’t tell any difference if I turn it off or not.

[Coolerking]

We build what you all are referring to as a "thin plate"
It has thermal mastic (paste)/copper tubing assembly encased in a very thin seam welded stainless steel box.
They work great for non holdover applications in what are usually small vessels, in drink boxes and such..
The white thin plates you see in your fridges/freezers are called roll bond dry evaporator plates, they are the most widely produced evaporator plates in the world.
Its amazing the abuse they can take, being so seemingly fragile, you would be amazed at the stuff I've seen...
What most folks outside the actual marine HVAC biz fail to realize is that the insulation and its install are the biggest thing in any system.
If I cant keep the heat out of the box, then I have a problem.
If I can't get the heat out of the boat, problem.
This is exactly what Yeti, and all the copy cat coolers have keyed on, good heavy multi angle seals, stout gaskets, an absolute vapor barrier.
Of course that comes at a price.
The smallest compressor can remove and maintain temps in nearly anything that has nearly zero heat energy input.
There is no such thing as "cold".
Only the lack of heat.

[GILow]

[QUOTE=nilespf;3087285]

Originally Posted by GILow

Just one more bit of info and that is the current draw when the reefer "system" is on from that I can compute the DC. ***********If I assume your DC is identical to mine that would put your draw at 5.5 A which is the same as my BD50 @ 3K RPM and the plate running @ 0 deg You may be correct, I'm inclined to think this data suggests it is about as good as it gets.


Pn

Close enough.. my draw is between 7 and 8 amps, but the DC is a bit under 30%. The lower DC is, I assume, a byproduct of the eutectic tanks. The tanks run between -14 C and -22 C.

[Buzzman]

GiLow and Richard K

I think you are both talkiing at cross-purposes. No-one is saying or implying that any energy is being created.

The CRUCIAL (and perhaps ONLY) advantage of the hold-over or eutectic plate system is that (and read this point carefully) when one has an excess of solar availability (i.e. full sun all day) and once the batteries have been topped up via the solar array, there is an "excess" (or remaining availability) of energy from the sun that could be utilised by being convereted into 12V electricity and that additional energy being used to drive down the temp of the eutectic/holdover plates.

that 'stored energy' can then be accessed at night to 'suck' heat out of the box, without having to run the compressor further, at which time it would obviously be running of the stored electricity in the house battery.

So the "extra energy" is that which can be accessed once the vessel's battery is replete, converted to 12V and then converted again via phase change into ice at the plate/s.

I'm thinking the only real advantage to this scenario would be for someone who ahs a small battery capacity and additional high usage in evening. For example, a TV, or stove or whatever.

For such a vessel, being able to "store" energy in the holdover plate would be advantageous.

But, as has been stated (over and over) it's way more efficient to increase the size of the storage battery and simply use 12V to run the compressor when required.

[Richard Kollmann]

Originally Posted by Uncle Bob

Richard, I couldn't find the original test results so reached out to Ozefridge for clarification. Here is part of the response regarding the order of the test.
The original thread with the test data (now removed from CF!!!) clearly indicated that the tests were done in sequence starting with the EUTECTIC system first, and therefore the cyclic system period benefited from the hold-over from the eutectic plate period.
This would seem to indicate to me that if either system had an advantage it was indeed the plate not the eutectic. Surely if the plate needed more power to keep the box at the existing temp that it was at the start of the test the results are clear.
As to your other points, yes the fridge needs to be switched on prior to use, preferably the day or evening before and as to you describing the system as a cycling plate, not a eutectic system, just pray tell what is the practical difference. It cools down to a predetermined point, switches off and switches back on when the temp rises to another predetermined point, keeping the box and it's contents within the selected temperature range.
The published results have apparently been mimicked by a number of happy customers who have put their hands up and said so, along with some that I have met on their boats who are also very happy.
Please, no more snow to confuse the issue, I just cannot understand your many and varied objections to this published test. I have no intention of participating in a rerun of the original bun fight so I guess I will leave it here.
Cheers.

You can paint that test any color you want, if it passes the smell test for you that is all that is important. Running eutectic test first then with the frozen plate still in the box the other compressor/ condensing unit ran in the same box without removing frozen eutectic plate. How could anyone rely on this methods of testing.

[GILow]

Originally Posted by Buzzman

GiLow and Richard K

I think you are both talkiing at cross-purposes. No-one is saying or implying that any energy is being created.

The CRUCIAL (and perhaps ONLY) advantage of the hold-over or eutectic plate system is that (and read this point carefully) when one has an excess of solar availability (i.e. full sun all day) and once the batteries have been topped up via the solar array, there is an "excess" (or remaining availability) of energy from the sun that could be utilised by being convereted into 12V electricity and that additional energy being used to drive down the temp of the eutectic/holdover plates.

that 'stored energy' can then be accessed at night to 'suck' heat out of the box, without having to run the compressor further, at which time it would obviously be running of the stored electricity in the house battery.

So the "extra energy" is that which can be accessed once the vessel's battery is replete, converted to 12V and then converted again via phase change into ice at the plate/s.

I'm thinking the only real advantage to this scenario would be for someone who ahs a small battery capacity and additional high usage in evening. For example, a TV, or stove or whatever.

For such a vessel, being able to "store" energy in the holdover plate would be advantageous.

But, as has been stated (over and over) it's way more efficient to increase the size of the storage battery and simply use 12V to run the compressor when required.

Actually, I am not advocating one system or the other. I have no horse in the race as I don’t sell or service this stuff for a living. All I care about is that the systems are represented accurately without a whole lot of emotive words and expressions with no factual backing.

This whole thread is dotted with silly phrases trotted out in the absence of hard facts. I would have ignored it completely if it were not for the clear invitation for anyone who’d had a good experience of the Ozefridge systems to step forward. I provided not only my positive experience but a couple of simple numbers for comparison, with no idea if those numbers are good or bad. They are good enough for me, but for all I know I may be using twice as much power as another system of the same size and function.

Those numbers have been ignored and instead a bunch of banal phrases and hackneyed adages have been trotted out to try to imply that there is something fundamentally wrong with a system that works perfectly.

This thread feels like a bit of gaslighting disguised as a real discussion, and with the leading questions in the opening post I am not surprised.

It’s a pity, because it was a good idea to collect the bad experiences as a way of helping others avoid the same pitfalls.

[RaymondR]

To my way of thinking the only items which matter in the tests Ozepete's company ran were:

Did the refrigerated enclosure stay at the same temperatures during the tests.

How many amp hours did each system, the eutectic, and the evaporator plate,
consume during the same periods at test.

If there are questions regarding evaporator plate sizing etc then the only way to resolve them properly is for the dissatisfied party to set up their own test bed and run their own tests. Anything else is just speculation.

Is my memory failing me or were the results of the tests re-posted here in an earlier post and are now missing?

[Q Xopa]

[QUOTE=Richard Kollmann;3087225]

Originally Posted by Q Xopa

First the second rule of thermo dynamics is Energy can not be created or destroyed.

Twelve volt electricity in watts of power is converted to Btu of energy in a compressor and at its highest Rpm there is a slight increase of energy Watts to Btu.energy. If compressor speed is reduced its volumetric efficiency of gas vapor is more efficient resulting a higher Coefficient Of Performance (COP). Reducing compressor speed achieve more efficient use of energy but will require compressor to run longer. There are some cases where compressor speed set to run at minimum speed can reduce daily energy consumption by 50%. You may have the correct matching energy capacity compressor, condenser and evaporator but efficiency is determined by compressor speed.

If the compressor at a preset speed is producing fixed Btu energy at a COP of 1.5 you would like to think each component of the complete Systems SCOP would match the compressor’s COP. It has been mentioned that eutectic plates improve the COP in a system but in fact they reduce SCOP because they are less efficient because they require more energy in the phase change of solution to ice. Again Eutectic plates used in conjunction with small 12/24 volt compressors are only of value if there is surplus energy from compressor to freeze them. Yes, on these small systems having energy stored in the box does help maintain box temperature when warm product is placed in box. Then the question is if you do not have surplus electrical energy is the loss of space taken by eutectic plate worth it.

Holding energy eutectic plates offer a good solution in off the grid applications that justify them. I have been asked to do a conceptual design for holding plates and refrigeration for 12 and 24 hours hold over time to be used for three walk in rooms. I am this week researching holdover plate companies for the refrigerated truck industry now.
There was a time the pleasure boat refrigeration industry Crosby, Grunert and many private boat owners with large cooling demands used these companies for manufacture ring their plates.

Yes now I agree with everything you have just said.

Previously you were saying other things about Compressors 'create energy' and Solar ONLY charges batteries and eutectic was only useful with solar.

[Uncle Bob]

Originally Posted by RaymondR

To my way of thinking the only items which matter in the tests Ozepete's company ran were:

Did the refrigerated enclosure stay at the same temperatures during the tests.

How many amp hours did each system, the eutectic, and the evaporator plate,
consume during the same periods at test.

If there are questions regarding evaporator plate sizing etc then the only way to resolve them properly is for the dissatisfied party to set up their own test bed and run their own tests. Anything else is just speculation.

Is my memory failing me or were the results of the tests re-posted here in an earlier post and are now missing?

Could this be what you are looking for?
https://www.ozefridge.com/trial-data
I also couldn't agree more about re running the tests by those that so ardently disagree, I look forward to viewing your results along with the testing methodology sometime in the next couple of months.

[RaymondR]

Originally Posted by Uncle Bob

Could this be what you are looking for?
https://www.ozefridge.com/trial-data
I also couldn't agree more about re running the tests by those that so ardently disagree, I look forward to viewing your results along with the testing methodology sometime in the next couple of months.

Yep that's part of it but there was also a log of temperatures posted with the first thread. you could see a small temperature rise in the eutectic trials when all the eutectic had melted.

If anything having the eutectic tank in the same test enclosure as the evaporator plate would assist in reducing the number of on/off cycles during the plate evaporator trial due to the hysteresis inherent in those systems and the thermal mass of the eutectic.

[Uncle Bob]

Originally Posted by RaymondR

Yep that's part of it but there was also a log of temperatures posted with the first thread. you could see a small temperature rise in the eutectic trials when all the eutectic had melted.

If anything having the eutectic tank in the same test enclosure as the evaporator plate would assist in reducing the number of on/off cycles during the plate evaporator trial due to the hysteresis inherent in those systems and the thermal mass of the eutectic.

If you want more send an email to pete at ozefridge and ask, he doesn't bite.

[a64pilot]

One thing to be aware of is that the majority of holding tank systems sold aren’t really Eutetic systems, in that the frozen liquid doesn’t melt at each cycle, and it’s not an Eutetic fluid either, it’s a mix of antifreeze and water, I assume because that’s easy and doesn’t cause corrosion, and food grade antifreeze isn’t toxic.
Mine for example is not, the fluid never melts, not unless you turn the power off anyway.
Only a few systems, and I believe the one in the test people are talking about actually phase change.

The purpose of and their best use is as they were originally designed, as a way to store excess power when it’s available and then to not run the compressor when it’s not, Back in the day before small very efficient DC electric compressors they were the bomb, you had a large compressor mounted to the engine Ala like in your automobile and whenever you ran your engine to charge batteries (cause Solar was only for rich people) you could freeze those plates down and they would keep the box cold until the next time you ran the engine to either motor or charge batteries.

But now that we have very efficient small DC compressors, the need of a hold over system isn’t as great as it once was.
Which doesn’t mean they aren’t good, just maybe aren’t the only system that will work anymore.
Pick a system that is simple, meant to be user serviced, good customer service, doesn’t have cool bells and whistles, has a good solid reputation and not because it has cold plates or not. Don’t get set on having to have one feature or not.

Ever wonder why even the newer very efficient house refrigerators etc don’t have cold plates? It’s because cold plates aren’t necessary for efficiency is why, if they were then surely Supermarket etc fridges would have them as that power bill has to be pretty large.

It’s a lot like water cooling, finally people have come to believe that you can have efficiency with air cooling, where before many thought due to waters greater ability to absorb heat, you had to have water cooling to be efficient.