Cold / Eutectic / Holdover / Holding plates and Energy Accumulators...

[ErikFinn]

Oh boy, did I miss a term?

I'm trying to refer to the same and one thing, the big metal box some of you may have inside your boat's fridges and/or freezer boxes... I suppose those terms all refer to the same item, but I might be wrong..

yea, this is what I'm referring to

Ok, so I'm in need of some education please. I need to re-do my fridge box from scratch and I'm trying to research and find out my best options.

In the old 200 liter freezer I have 4 (four) cold plates, but this thing was powered by a huge lump of a 12 volt noisy electric motor driving a huge compressor and I just don't want to have anything to do with that boogie man system.

But I want to learn more about the cold plates please (I also have one in the fridge, plus a plate evaporator). Apparently these are not so cheap, starting at around 400 - 500 USD each, depending on source and size, and I'm trying to find out if I should re-use these cold plates for my fridge, and later maybe for the freezer. Or just toss them.


I'd have some questions please:


1) Do these things have a short service life or do they essentially last a very long time? Are they prone to corrosion for example? What usually goes wrong with them if anything? Do they develop leaks? What is your past experience with these things?


2) I understand every cold plate requires it's own controller? Or how is the operation of the cold plate controlled and timed? Not just with a thermostat? I know you can have different solutions of Propylene Glycol inside them for different temperatures of thawing/freezing of the solution, but how do you control the running of the compressor?

For example, this WAECO VD-06 Energy Accumulator has a separate controller .

These Ozefridge Eutectic plates (about 1/3 down the page) seem to use the controller which is incorporated in to the compressor/condensing "mother unit" A480?


Where can I find and compare and buy these controllers separately? I have not found one single shop or source for the controllers so far.. Do they even exist?

[Neptune's Gear]

Here. http://www.neptunes-gear.com/index.p...igeration.html
Let me know if you need any further info.

[Richard Kollmann]

I want to learn more about the cold plates please (I also have one in the fridge, plus a plate evaporator). Apparently these are not so cheap, starting at around 400 - 500 USD each, depending on source and size, and I'm trying to find out if I should re-use these cold plates for my fridge, and later maybe for the freezer. Or just toss them.

Question: Why Eutectic holding plates instead of a more efficient standard evaporator plate?
In mobile refrigeration energy is not always available 24 hours a day to run a mechanical refrigeration unit. Direct current on board power grids 12 or 24 volts on boats under 50 ft are limited to smaller refrigerator/freezers daily energy demands.
Eutectic holding plates serve only one purpose and that is to STORE SURPLUS energy. Surplus energy generally comes from alternative sources Solar Panels, Wind generators, Water wheel generators, onboard generators or when connected over night to shore power battery charger. Small 12/24 volt compressors rarely can provide surplus energy to holdover plates. Technautics model Cold Blue refrigeration unit when installed on small heat loaded boxes is the exception to the surplus energy rule by operating compressor at its lowest speed running more hours a day for best efficiency.

1) Do these things have a short service life or do they essentially last a very long time?

• Life of a Holding Plate will depend on manufacturer’s design and their quality control and materials used, with luck your plates can last 30 + years. One fact you must understand is a plate designed for a particular size compressor can not be expected to work for long if a much smaller compressor is used, this is do to the lower velocity of oil return flow to compressor.

2) I understand every cold plate requires it's own controller?

• Connecting holding plates in series with only one refrigerant control device makes it almost impossible to control refrigerant flow. Series connected plates means that superheat, conversion of heat absorbing liquid to gas vapor inside each plate, will not be equal in each plate. Another reason for controlling each plate separate is faster refrigerant flow to each plate and an opportunity to control flow separately to refrigerator and freezer plates reducing compressor running time.

Temperature of holding plates will be determined by selecting one of three ways, Running time of compressor if timer is used or a Low pressure Switch or one or more thermostat.

Holding plates in boat refrigerators normally have food grade propylene glycol and water mixtures set to freeze at zero to +6 degrees in freezer plates and +26 degrees F in refrigerator plates. For 24 hours holdover my designs call for one gallon of solution for each cubic ft of freezer space and ½ gallon of solution for each cubic ft of refrigerator box.

One reason holding plates are not as efficient as standard evaporators is to freeze all solution in plate solid temperature in plate coil must reach 20 degree below eutectic point do to loss of thermo conductivity of ice formation in plate. With the exception of pure water as a frozen solution eutectics melting create a bias temperature rise of holding plates as solution melting occurs.

[SV THIRD DAY]

Originally Posted by ErikFinn

Ok, so I'm in need of some education please. I need to re-do my fridge box from scratch and I'm trying to research and find out my best options.

In the old 200 liter freezer I have 4 (four) cold plates, but this thing was powered by a huge lump of a 12 volt noisy electric motor driving a huge compressor and I just don't want to have anything to do with that boogie man system.

But I want to learn more about the cold plates please (I also have one in the fridge, plus a plate evaporator). Apparently these are not so cheap, starting at around 400 - 500 USD each, depending on source and size, and I'm trying to find out if I should re-use these cold plates for my fridge, and later maybe for the freezer. Or just toss them.


I'd have some questions please:


1) Do these things have a short service life or do they essentially last a very long time? Are they prone to corrosion for example? What usually goes wrong with them if anything? Do they develop leaks? What is your past experience with these things?


2) I understand every cold plate requires it's own controller? Or how is the operation of the cold plate controlled and timed? Not just with a thermostat? I know you can have different solutions of Propylene Glycol inside them for different temperatures of thawing/freezing of the solution, but how do you control the running of the compressor?

For example, this WAECO VD-06 Energy Accumulator has a separate controller .

These Ozefridge Eutectic plates (about 1/3 down the page) seem to use the controller which is incorporated in to the compressor/condensing "mother unit" A480?


Where can I find and compare and buy these controllers separately? I have not found one single shop or source for the controllers so far.. Do they even exist?

These are Holding Plate Basic questions 101....so lets take the questions in order and keep things easy to understand and apply.

1.
Holding plates typically have a much longer lifespan than a thin rolled aluminum evaporator, mainly as a function of their more robust construction. We have 30yr old holding plates out in the field working today and it’s a standard procedure for us to recycle holding plate and convert them to be operated from a 12v low power draw compressor. Everything can corrode or can develop leaks, but going back to the materials of construction for holding plates vs rolled thin aluminum evaporators, holding plates are much less prone.

2.
The compressor and compressor controller does not care what type of holding plate it is running…it is the simple off the shelf Thermostat that controls the running of the compressor based on a set-point to keep the holding plate eutectic solution from defrosting as it absorbs heat from the Box. So the only difference between a freezer and refrigerator holding plate for example is the Thermostat and the concentration of the eutectic solution put inside the holding plate.

If you need any help just give me a call or shoot me an email 7 days a week.

Phone: 619-609-3432
Email: Info@TechnauticsInc.com

[Richard Kollmann]

Erik Finn, So there is no misunderstanding I do not recommend the Technautics Cool Blue unit for your 200 Liter (7 cu ft ) box in a tropical climate unless boat is equipped with extensive alternative energy.

[SV THIRD DAY]

We wouldn't want a miss understanding of what your opinion is Richard, so thanks for the clarification. But as far as I understood the question, this wasn't a "what type of system should I buy" thread, it was a Q/A about holding plates.

We have played this game before, its too bad that you think building holding plate refrigeration systems since 1968 doesn't qualify us as having some valuable input and you seem to view our comments on things we know as some type of BS marketing sales approach. Don't need that my friend, since I can barely keep up with the 15-20 systems we are selling per month (22 in April) that ARE indeed going to the tropics with 7CF boxes and larger. We are shipping two systems to the Philippines, one to Puerto Rico, and one to the Virgin Islands today via DHL. Happy client reviews documenting their low power usage and Cold Beer and Ice Cream are all I need to be happy and overworked. So, offering up a little expertise for free to the cruising community is just what I enjoy doing while working from my boat chart table floating on the mooring. Heck its either that or do my own long list of boat projects...uggg...what fun would that be!


Regards

[Richard Kollmann]

Rich I was addressing this boaters question: “In the old 200 liter freezer I have 4 (four) cold plates, but this thing was powered by a huge lump of a 12 volt noisy electric motor driving a huge compressor and I just don't want to have anything to do with that boogie man system.”

Four holding plates with probably oversized evaporator coils inside a 7 cubic ft box is not a replacement candidate for a Cool Blue unit if freezer temperatures are required in a tropical climate. Yes both of us are dealing with more than 50 years experience in mechanical engineering and my opinions are formed from hundreds of boaters actual performance reported experiences over the last twenty five years. Unfortunately many systems marketed as Ice box conversion units for refrigerators turn out to operate as drink coolers in warm climates. Rich, There is a large market for your small energy efficient unit’s application. I just question in this case if it would be a good choice.
I will continue to express my opinions when I believe the application of a system may not perform as advertised.

[SV THIRD DAY]

Originally Posted by Richard Kollmann

. I just question in this case if it would be a good choice. I will continue to express my opinions when I believe the application of a system may not perform as advertised.

But here's the problem...I never said a CoolBlue 12v condensing unit would be a good fit for a 4 plate system...hell that would be CRAZY. The issue of recycling holding plates was address as something done all the time by us and others, but no one in their right mind would put a Danfoss simular type DB35 or 50 on a 4 plate system. So the disagreement really isn't....we are on the same page on this one!

Cheers

[Neptune's Gear]

Richard, you have more experience than I do with these systems. Perhaps you could answer a question for me? In your post above, you say "Question: Why Eutectic holding plates instead of a more efficient standard evaporator plate? "

This is not my understanding, nor my experience. Here is my viewpoint;

I believe Eutectic systems have many advantages including the following..
1/ Long ‘hold-over’ off periods due to the large thermal mass and more importantly because of the eutectic’s phase change.
2/Refrigeration can be at a time that suits the power supply, or during cooler periods when refrigeration systems are more efficient.
3/Much lower overall power consumption due to more efficient refrigerant evaporation in a saturated environment,
4/With ECO2 (Ozefridge smart controller) the eutectic mass is automatically refrozen whenever sources of power are abundant, (solar,wind,shore power, genset, engine, whatever brings up the voltage) reducing demand on batteries.
5/Virtually ‘cooling in advance’, use of abundant power supplies provides a day or so of refrigeration requirement in storage.
6/A day or two of sailing without the need of additional cooling is possible if battery power supply is down. (i.e. solar but no sun!)
7/Eutectic systems store energy at a third of the weight that would be required in batteries to provide the same refrigeration effect.

I'm only a re-seller and user, not a designer. I have an OzeFridge eutectic system in my own boat, cooling a 290ltr freezer to between -15c and -21c, AND a 290ltr fridge, both cooled by the same unit. On the equator it ran approx 30% of the time and draws about 5.5 amps. This is not theoretical. It is well tested, over about 4 years and many miles.

This is the most efficient 12v refrigeration system I have seen. Rich's one sounds pretty good as well, but I have no personal experience of them. I have seen a lot of systems in 40 odd years of sailing.

Perhaps you could point out where my understanding is flawed?

Always ready to be further educated!

Thanks
Matt

[ErikFinn]

Originally Posted by Neptune's Gear

Here. Ozefridge Marine Refrigeration Boating Gear fit for the King
Let me know if you need any further info.

Hi Matt and thanks for your kind reply.
Would I be able to use my old cold plates with say the A480? Or would I have to get the OzeFridge cold plate for a fridge application?
Does the A480 come with quick couplings? I would have to be able to do the connections myself as here I can't find a competent fridge tech, so do you also sell the quick couplings separately to fit my old plates so I could re-use my old ones?
Cheers,
Erik

[ErikFinn]

Originally Posted by SV THIRD DAY

2.
The compressor and compressor controller does not care what type of holding plate it is running…it is the simple off the shelf Thermostat that controls the running of the compressor based on a set-point to keep the holding plate eutectic solution from defrosting as it absorbs heat from the Box. So the only difference between a freezer and refrigerator holding plate for example is the Thermostat and the concentration of the eutectic solution put inside the holding plate.

Thank you Rich for your kind reply.
Would you be able to provide a link to good suitable thermostat shop that I could use in an icebox/fridge application utilizing my old cold plates? Ideally I would like to be able to study and compare different products.
Regards,
Erik

[ErikFinn]

Originally Posted by Richard Kollmann

Erik Finn, So there is no misunderstanding I do not recommend the Technautics Cool Blue unit for your 200 Liter (7 cu ft ) box in a tropical climate unless boat is equipped with extensive alternative energy.

Thank you for your kind help Mr. Kollmann.
At this moment I would like to establish if it is feasible (techically abd economically) to re-use my old cold plates.
I have about 700W solar and a a 400W wind genny, but all are old equipment. However, I must start planning from something and research and education can't be to wrong...
Regards,
Erik

[ErikFinn]

Originally Posted by SV THIRD DAY

We wouldn't want a miss understanding of what your opinion is Richard, so thanks for the clarification. But as far as I understood the question, this wasn't a "what type of system should I buy" thread, it was a Q/A about holding plates.

That is correct. Pardon me but I really do not understand the workings of these "Cold / Eutectic / Holdover / Holding plates and Energy Accumulator" systems so I am merely trying to learn and patch my ignorance for now. I would hate to do a total fail system, but also I am on a budget. So I try to learn. And I'm hoping to find out it would be a great idea to re-use my old plates, as I have 5 of them. Albeit 4 in a non-working freezer ( I already removed the 12V electric drive motor and the compressor), and one in the fridge ice box)

My first project is to re-do the 175 liter icebox fridge, maybe s spillover system. The separate 200L freezer can wait for now.

regards,
Erik

[Richard Kollmann]

In a tropical climate a 175 liter refrige and 200 liter Freezer it is unlikely one or even two small BD compressors could provide the daily Btu DC power you will need.

Yes, You can use the five present holding plates if the correct size compressor condensing unit is installed. How well did the old system work? How large is compressor? Did you need to run an engine for refrigeration to work? Do you know manufacture of present system.

For the size boxes you have and in a hot climate I would first recommend removing present system complete. Reduce size of boxes by adding Water resistant Extruded Polystyrene panels DOL Blue Board type insulation to interior of box. With both boxes 4 cu ft or less Two BD50 compressor condensing units one for each box is an option I would consider.

Any way you approach this refrigeration problem costs for a reliable system are going to run $3 to $4,000. Without knowing more about the boats DC power Grid I am concerned about available daily amp-hrs consumed.

[Richard Kollmann]

Matt, Early holding plate refrigeration began in the refrigerated truck industry and still are used today Holding plate boat refrigeration became popular on the US East Coast by Grunert and Crosby companies. Twenty five to 50 pound eutectic solution plates made by Dole were popular on 40 ft charter sailboats powered by engine driven one and two horse power compressors. One hour running time a day with one of these compressors producing 6000 Btu and could freeze several holding plates solid. A single BD50 compressor system at + 10 degrees F delivers only 500 Btu in one hour per Danfoss application engineering spec sheet. Unfortunately to freeze eutectic solution evaporator coil in holding plate must be at least 10 degrees below a set freeze point of solution and this added demand will reduce Btu efficiency of compressor.

Eutectic holding plates are really sluggish evaporators that permit surplus energy to be stored. A small BD35 or BD50 or even a BD80 used for a small pleasure boats refrigeration will have little surplus energy available when they are operated at an efficient speed energy mode. Standard evaporators provide faster box pull down temperatures and a more stable box temperature than a hold over plate. Box temperatures with thermostat that are controlling evaporator can be maintained to within 2 degrees. Holding plate to be efficient demand extended compressor off cycles allowing box temperature to increase 10 to 15 degrees. Another disadvantage of holding plates is many times they lack enough exposed surface area necessary to except the incoming box heat load.

The purpose of an evaporator whether standard Roll-Bond thin aluminum plate or refrigerant tubing inside a holding plate is to absorb heat from refrigerated box and dispose of it outside area of refrigerator. Standard aluminum evaporators are great conductors of heat. Most eutectic plates are poor conductors of heat because of thermo losses in getting through plate skin, ice formation and final evaporator coil material. In reverse when trying to store energy in plate by freezing solution a lower temperature in plate’s evaporator will be required this ends up decreasing compressor btu output.

Your Items 1, 2 , 3 and 7 Are good for creative marketing otherwise I see them as meaningless statements. Where would energy come from without batteries if alternative energy was not adequate?
1/ Long ‘hold-over’ off periods due to the large thermal mass and more importantly because of the eutectic’s phase change.
2/Refrigeration can be at a time that suits the power supply, or during cooler periods when refrigeration systems are more efficient.
3/Much lower overall power consumption due to more efficient refrigerant evaporation in a saturated.
7/Eutectic systems store energy at a third of the weight that would be required in batteries to provide the same refrigeration effect.


Items 4,5,6 I agree, Holding plates on BD 12 volt compressor systems are only practical if there is surplus energy from another alternative energy source.

4/With ECO2 (Ozefridge smart controller) the eutectic mass is automatically refrozen whenever sources of power are abundant, (solar,wind,shore power, genset, engine, whatever brings up the voltage) reducing demand on batteries.
5/Virtually ‘cooling in advance’, use of abundant power supplies provides a day or so of refrigeration requirement in storage.
6/A day or two of sailing without the need of additional cooling is possible if battery power supply is down. (i.e. solar but no sun!)


I suppose it is not correct to say that all eutectic holding plates are less energy efficient than standard evaporators because there are good and bad designed holding plates. When I was in the holding plate business I was able to cut open many other companies plates to see how heat movement was handled in each plate. Dole in Tenn. Was and is still the best in holding plate designs. Twenty seven years ago Dole fabricated holding plates for the for charter and pleasure boats. Dole still uses the basic design today in their truck plates as they did for our industry attaching evaporator to the back of front plate surface improving performance of most plates used by our industry. Frigoboat engine drive systems at one time had large stainless plates, when I cut one open it looked like a car radiator covering complete area inside. SeaFrost’s cast aluminum block plates that perform exceptionally well had a basic copper coil inside with added copper sheet plate as a heat conductor. Gleaser Bay had a good heat conducting plate using mutable small spider evaporator coils inside but as with most or their products thing did not work out for them.

Many holding plates today are fabricated from Stamped food serving table trays Techantics continuous spot welds backs on pans, OzeFridge bolts back cover on pan using a gasket to retain solution. I built mostly custom stainless holding steel plates to fit any size and shape required from one gallon of eutectic solution to 27 gallons. Sixty of these plates are shown in my DIY book. I also built around 200 holding plates using the serving table tray pans. I used various techniques to improve heat conduction of plates from fin coils to attaching coil or wedging refrigerant coil to plates surface. Plates from pans were always mounted ½ inch away from liner to expose more surface area helping the natural tumble of box air. A boater can always see if heat is conducted through plate surface quickly if beginning plate pull down frost shows where inside evaporator assembly is in contact with plate’s surface.