Who provides the best 12 volt refrigeration systems?

[OzePete]

Originally Posted by rgleason

My experience with the ozifridge eutectic system and some informal testing to get the right solutuon of antifreeze/water is that the solution does not all freeze at exactlty the same temperature. You might think it should but it doesn't. There as if freezes there will be a range of a couple of degreesC and I forget exactly how much.

Since doing this many years ago there have been new companies specializing in eutectic solutions. Has anyone tried discussing our particular needs to come up with a better solution that might be more efficient, precise, or hold motre btus?

Great subject RG.
Once glycol or any dissimilar material is mixed with water the phase change temperature widens and that is of great co-incidental benefit.
As we know when we freeze water it expands with considerable force if contained. The mix allows expansion to occur while still a slurry only mostly solidifying once expanded. If the eutectic mix acted like water our eutectic plates would look like pumpkins!

One trap if using auto coolant is the confusion of the labelling. The temperature referred to on the coolant pack is the temperature before any solidification occurs not the freeze point. Best to relate to the glycol % and mix a brew accordingly and always make sure a florescent colour is present, better still use food grade glycol!

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[a64pilot]

Very few “eutectic” systems use an eutectic fluid.
I think you can get a eutectic fluid with salt, but have to deal other properties of salt of course.

Getting a eutectic system “right” is tough, you have to match it so that the freezing temp of the plates result in the temp you want your freezer or fridge to be at, or accept the temps that you end up with.
A true eutectic system won’t have an adjustable thermostat, cause if you change the temp, it’s not a eutectic system anymore.

This is not to say that cold plates don’t work, or course they do, just not many are really eutectic systems is all.

[Richard Kollmann]

Originally Posted by rgleason

My experience with the ozifridge eutectic system and some informal testing to get the right solutuon of antifreeze/water is that the solution does not all freeze at exactlty the same temperature. You might think it should but it doesn't. There as if freezes there will be a range of a couple of degreesC and I forget exactly how much.

Since doing this many years ago there have been new companies specializing in eutectic solutions. Has anyone tried discussing our particular needs to come up with a better solution that might be more efficient, precise, or hold motre btus?

Rgleason, Glycol and water are not a true Eutectic Solution as the specific gravity of each is different allowing them to separate over time. As long as the plate is frozen water and glycol remain as a solution. It has always been believed by those of us in the eutectic plate business that the dynamic motion of a boat will keep the solution in a balanced specific equal gravity state. Glacier Bay Marine refrigeration experimented with the so called Super Eutectic Solutions and that may have contributed to their getting out of the refrigeration business.

The refrigerated trucking industries are the ones who introduced Eutectic plates to the mobile refrigeration industry and the marine refrigeration groups. Dole a company in Tennessee built the holding holdover plates for Crosby and Grunert as well as many private boat owners. These true brine solution eutectic plates were constructed from carbon steel using evaporator coils attached to plate inside surfaces. Dole’s designs eliminated inside corrosion failures by adding additional neutralizing solution chemicals. Removal of air from ice expansion space replacing it with nitrogen then permanently sealing the solution tank is why 35 year old plates are still in service today. These Dole plate are easy to identify as they were cold galvanized gray or white with liquid fill plug welded shut.

You can take a horse to water but you can not make him drink...

[OzePete]

Originally Posted by a64pilot

Very few “eutectic” systems use an eutectic fluid.
Great subject, but hard to keep simple! .. Using water (The purest eutectic material) would see the eutectic tank expand hydraulically and be damaged, besides water phase changes at 0c so not much good for fridge / freezer application. Adding a % of glycol to water shifts the phase change temperature lower, relative to the mix rate, but does reduces it's 'thermal storage' ability slightly. .

I think you can get a eutectic fluid with salt, but have to deal other properties of salt of course. Yes but as you suggest, at what risk?

Getting a eutectic system “right” is tough, you have to match it so that the freezing temp of the plates result in the temp you want your freezer or fridge to be at, or accept the temps that you end up with.
It can be done, we have been doing this for decades. We have found it best to offer two phase change temperature options. One for refrigerators the other for freezers. Thereafter if cabinet temperature needs adjustment, moving the SET point will alter cabinet temperature without losing the benefit of phase change. This assumes that the correct size eutectic plate(s) was supplied in the first place. And that is why we always insist on providing a heat load and power consumption estimate specific to each project, before supplying systems.

A true eutectic system won’t have an adjustable thermostat, cause if you change the temp, it’s not a eutectic system anymore.Not all, We fabricate all our eutectic plates with a 3’8 diameter ‘dry well’ that allows the sensor probe to sense the centre of the eutectic mass. The SET point (off) is lower than the freeze temperature of PCM and the HYS is 8C meaning the restart is only after the PCM has thawed, providing proper control and the full efficiency benefit of the phase change from every cycle.

This is not to say that cold plates don’t work, or course they do, just not many are really eutectic systems is all.Absolutely agree 100%. Eutectic systems get bad press (fake news!) because most are simply not phase changing therefore not much more efficient than a thin cyclic plate. If a ‘Eutectic plate system is not allowed or controlled to freeze the mass solid on every run cycle and then remain off until it has absorbed enough heat from the cabinet to thaw that mass, then IT IS NOT OPERATING AS A EUTECTIC system. Period!

More on eutectic systems and correct control (Sure-Thaw) here: Why Eutectic | Ozefridge

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[Richard Kollmann]

Originally Posted by a64pilot

Very few “eutectic” systems use an eutectic fluid.
I think you can get a eutectic fluid with salt, but have to deal other properties of salt of course.

Getting a eutectic system “right” is tough, you have to match it so that the freezing temp of the plates result in the temp you want your freezer or fridge to be at, or accept the temps that you end up with.
A true eutectic system won’t have an adjustable thermostat, cause if you change the temp, it’s not a eutectic system anymore.

This is not to say that cold plates don’t work, or course they do, just not many are really eutectic systems is all.

If you freeze water inside metal tank you have stored 144 Btu of energy per pound of ice. As long as there is some ice left in tank the liquid left will be held at 32 degrees F.
If a zero degree F mixed eutectic solution is frozen in the same tank there will also be near 144 Btu of energy stores per pond of ice. The difference water ice and eutectic solution ice is in a tank is the length of time the desired refrigerator temperature is controlled..

If eutectic Glycol solution stays premixed so all of it has a zero degree F eutectic freeze point and then exposed to a temperature of – 20 degrees F solid ice. This is what temperatures will actually be inside plate if compressor is not allowed to cycle normally. At minus 20 degrees ice temperature only ½ of a Btu per pound per degree is stored so within a very short time plate temperature will reach the zero eutectic freeze point. Once at the eutectic temperature point the eutectic solution starts melting at a much faster rate than water ice alone. With loss of ice volume temperature of plate will continue to rise until ice volume is low. When ice can no longer produce needed Btu heat absorbing temperatures will rises rapidly consuming only one Btu of energy per pound per degree of cold liquid solution.
When eutectic plate on small less than 1000 btu compressors can not maintain desired refrigerated box temperatures the unit becomes a cycling eutectic plate system and no more efficient than a standard evaporator.

Energy to be stored in eutectic plates is not created by the eutectic plate as some believe. Only the compressor can produce surplus energy to store in holdover or even compressor cycling eutectic plates. The only way to justify eutectic plate refrigeration when compressor is too small is to have alternative energy wind or solar. Eutectic cycling single plates are useful in coolers but they are less reliable as food storage freezers.

[john61ct]

I sure wish someone could rewrite that in a way that I could understand it.

I tried, I really did.

If you grok that Pete you think you could give it a go, in the name of coopetition?

[Singularity]

Originally Posted by nmccubbin

We are about to buy a small compressor/condenser using with an evaporator plate to add to out mechanical system. Reason is backup and to let our solar panel and windmill do some of the work.....

Much of the information here is from the vendors. While very useful on the technical side, it does not provide independent opinions.

From what I can see, you expressed your concern that you had surplus solar energy that you wanted to bank, and then asked for independent advice on refrigeration.

What I see happened is response is that a few tried to help, but then the vendors jumped in and all over each other, none of the vendors giving you anything other than a sales pitch for their products. [mods, please don't close the thread, if anything leash them]

In my opinion, you need none of their products and should not give them your business (regarding refrigeration) unless you have some very specific and peculiar concerns. Why? LiFePO4.

Option A:
$2500 pretty marine grade refrigeration unit, lasts 20 years, need to build and install box. Replace house batteries every ? years.

Option B:
$2000 400AH (12v) LiFePO4, <$500 pure sine converter, $300 dorm/office 100v fridge. Replace house batteries every ?+5 years, replace $300 fridge every 3-5-9 years. And you have a LiFePO4 bank!

[newhaul]

Originally Posted by Singularity

From what I can see, you expressed your concern that you had surplus solar energy that you wanted to bank, and then asked for independent advice on refrigeration.

What I see happened is response is that a few tried to help, but then the vendors jumped in and all over each other, none of the vendors giving you anything other than a sales pitch for their products. [mods, please don't close the thread, if anything leash them]

In my opinion, you need none of their products and should not give them your business (regarding refrigeration) unless you have some very specific and peculiar concerns. Why? LiFePO4.

Option A:
$2500 pretty marine grade refrigeration unit, lasts 20 years, need to build and install box. Replace house batteries every ? years.

Option B:
$2000 400AH (12v) LiFePO4, <$500 pure sine converter, $300 dorm/office 100v fridge. Replace house batteries every ?+5 years, replace $300 fridge every 3-5-9 years. And you have a LiFePO4 bank!

???? What does a dorm fridge and an inverter have to do with augmenting his current installed engine driven system? They need a 12 volt system to take advantage of the afternoon excess solar output. I stated my personal preferences and experiences wrt the companies and systems I have experience with. A dorm fridge won't do the op any good .
What are your experiences with 12 volt ice box conversion systems? That is what the op is looking for.

I do agree with you that there is to much of a measuring contest going on here now .
I however have a feeling the op has made a decision by now .

[rgleason]

I find the eutectic system to be ideal because it can be run at opportune times when the engine is on (turn unit on to full power) or solar pv is available and then with the 12hr period varying with the outdoor temp, it will not need any energy for a long time. Our system does not have solar yet, but we need to recharge the batts every other " freeze-up" so basically we can run the engine 1 every day. We usually get the fridge going earlier in the morning for a cople of hours, the turn the engine on motoring out of harbor and the volt sensor kicks the compressor to full power. Then after an hourc or so we will have wind and turn the engine off having brought the batteries up to 85-90 % charge. This is where we need more solar, the refridge will operate a little longer at a more efficient speed until the eutectic is frozen, For our solution that cut of is -6c or -7c, because the eutectix freezes over a couple of degrees.

With the ozifrige only needing less than 5 amps to operate, solar is a very good match with a eutectic system. If you could have panels that ran the refridge and would charge the batteries from 85%SOC on most days you would hardly need the engine. At sea it is a different story, generally with higher demands from nav equipment etc.

[longjonsilver]

To all: this has been a very good discussion especially for someone who has a little science/engineering background. While i know what a eutectic solution is, i had to look up hysteresis, and i am not sure yet how it relates to a eutectic solution. Anyway, in spite of the emotional outbursts of some of the participants, we have had a good exchange of ideas. i recently bot a compressor and a holding plate at a good price with the idea that i could use it in a boat that i was planning on buying at that time. Since then my plans have changed, and i have learned a lot more about refrigeration from threads like these. i guess i have two questions: 1) Would i be better off going with a more expensive system from ONE supplier, or buying components to match that which i have already bot? 2) Can anyone enlighten me on a water cooled compressor that uses the water tank on the boat instead of seawater? Until today, i never heard of such a thing.
jon

[weavis]

Originally Posted by longjonsilver

, I had to look up hysteresis, and i am not sure yet how it relates to a eutectic solution.
jon

I did too... As a medic I thought it applied to menopause...

My bad.

[a64pilot]

Hysteresis is usually used to to explain play or slop in a mechanical system, as well as even electrical, it may be misused, I likely used the term.
In a mechanical system for example a throttle cable can be said to have hysteresis as its being used to both push and pull, and when you change from pushing to pulling, you have a lot of slop.

I’ll try to explain what I think the gist of Richards post was, but I’m not going to dissect it.
1. Very few if any eutectic systems are actually eutectic, a true eutectic system will freeze completely and thaw completely holding the same temp, that is largely why it’s desirable. Most systems use a mix of Glycol and water and begin freezing many degrees before they become a complete solid, if they ever become a complete solid.
2. As this non eutectic mix begins to thaw it is absorbing less and less heat, making it less and less efficient as it thaws, where it would stay closer to the same if it were a true eutectic fluid. Same as it’s freezing, it’s a less desirable storage medium, however it is spread over several degrees, not just one exact temp like a true eutectic is. Reading into what Richard has said is what give Pete’s system the ability to adjust the temp within a rage of temp, if it were a true eutectic, you really can’t adjust temps much at all without losing the eutectic’s advantages and Richard explains why, cause once frozen, the solid will absorb much, much less energy per degree of temp change. It still works, just your maintaining RPM of that flywheel as opposed to spooling it up and letting it slow down
Remember to use a mechanical explanation, the eutectic tank is a huge flywheel.
3. Once a fluid is completely frozen, it’s ability to become an energy storage medium decreases drastically, it’s the phase change that absorbs and releases the heat, way more than just mass, so if your turning the temp down past the freeze point, your losing some advantage of having a eutectic system.

Actually what Richard was doing was merely explaining in a little more technical terms the operation of a true eutectic system, and what is usually sold as a eutectic system, but he was just stating facts, however he was also explaining in technical terms, why Pete’s system works to a great extent, he explained why / how Pete’s system can have an adjustable thermostat and still function to some extent as a eutectic system, not a pure one, but a system that can take advantage of the energy storage medium of a cold plate.

Now this is my opinion, and very often people do not hear what has been said or written, we put our own spin into it, it’s human nature

[a64pilot]

I’ve been in this thread a lot, and I enjoy greatly the technical explanations, cause it goes along with what I did for a lot of my adult life, but it really doesn’t have a whole lot to do with choosing a fridge.
In my opinion you want to chose from the following in no particular order of importance.

1. Simple, COTS system COTS stands for Commercial Off The Shelf, meaning you can get the parts from many different sources, also ideally a system if possible that can be operated in a degraded mode if some of the components fail is desirable, but really it’s as simple as KISS is desirable. You want a system that is easily serviceable, isn’t real critical as to charge level and comes with fittings that allow you to connect to, to replace a charge and you don’t have to cut into the system to solder in connection ports. Sight glasses are nice.

2. Customer support, you want to if at all possible to be able to call on the phone and speak to the person that can really help you trouble shoot and has the authority to break policy if you will and expedite you a part if you need one, and ideally tell you where you may can get the part cheaper and faster if possible yourself. You do not want your call to go to a call center where you hope to eventually escalate it to a level where you can get help.

3. Maybe a system that there is a lot of them out in the field, so that if you don’t do your own work, the there is a lot of knowledge about that system among fridge techs.
However a fridge once you understand it, is such a simple system that if you haven’t gotten one that is unnecessarily complex with neat features and lights and solid state electronics, You really need to learn about it and do the work yourself, and that is where a knowledgeable person on the phone that will walk you though the steps is priceless.
If you get a complex one, maybe consider carrying a spare electronics module, cause most require replacement with the identical part, they are tough to work around without extensive knowledge, sometimes.
Broken down to its simplest form, a fridge will still have one proprietary component that you can’t do without, that is the compressor electronics module, I’d suggest carrying a spare one of those, and maybe a condenser fan, a can of refrigerant and a service hose. Compressors are extremely long lived and reliable and are beyond most to replace anyway, not that I have seen all that many systems, but I don’t think I have ever seen a compressor fail.
4. Efficiency, you don’t want to buy an inefficient fridge, but in truth they are all probably pretty close to each other, at least the quality ones anyway, there are many ways to skin a cat, and in my opinion, the R value of your fridge box is where you gain efficiency, not by features of one fridge over the other.

Oh, and a lot has been said about the energy storage ability of a cold plate, and that is real, it exists and is a strong advantage of one.
However a very similar thing can be accomplished with another battery in the bank, store the excess power chemically as opposed to temperature. So you can emulate if you will the hold over ability of a cold plate with a battery, but don’t have to give up all that box space.

There is more than one way to skin a Cat

[a64pilot]

Originally Posted by longjonsilver

To all: this has been a very good discussion especially for someone who has a little science/engineering background. While i know what a eutectic solution is, i had to look up hysteresis, and i am not sure yet how it relates to a eutectic solution. Anyway, in spite of the emotional outbursts of some of the participants, we have had a good exchange of ideas. i recently bot a compressor and a holding plate at a good price with the idea that i could use it in a boat that i was planning on buying at that time. Since then my plans have changed, and i have learned a lot more about refrigeration from threads like these. i guess i have two questions: 1) Would i be better off going with a more expensive system from ONE supplier, or buying components to match that which i have already bot? 2) Can anyone enlighten me on a water cooled compressor that uses the water tank on the boat instead of seawater? Until today, i never heard of such a thing.

jon

I don’t see any compelling reason that any water cooled system can’t be plumbed into the fresh water tank.
It will add some heat of course, about as much as a 60W light bulb when it’s on, if it’s only water cooled, much less if air and water, how well insulated your tank is will have a lot to do with how easily it removes the heat. I doubt that many notice the additional heat

[john61ct]

Originally Posted by Singularity

you need none of their products and should not give them your business (regarding refrigeration) unless you have some very specific and peculiar concerns. Why? LiFePO4.

Option A:
$2500 pretty marine grade refrigeration unit, lasts 20 years, need to build and install box. Replace house batteries every ? years.

Option B:
$2000 400AH (12v) LiFePO4, <$500 pure sine converter, $300 dorm/office 100v fridge. Replace house batteries every ?+5 years, replace $300 fridge every 3-5-9 years. And you have a LiFePO4 bank!

Having a big higher CAR storage bank is no reason to accept lower efficiency in the fridge.

There are mains home fridges more efficient than 12V compressor portables like Engel, but not sold afaik in NA market.