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Old 25-08-2015, 15:21   #1
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Are holding plates "old" technology?

Its time to upgrade the fridge.

We currently have a big fridge with an evaporator bin.

The evaporator has a pin hole and the fridge insulation is 27 years old. We are looking at building separate units for the fridge and the freezer.

We were thinking of a holding plate, like Technautics, for the freezer because everything is just being kept below freezing and we want to realize lower power use.

We were also thinking about sticking with an evaporator system for the fridge so we have more control over fridge temps.

What's the feedback on holding plate technology vs. evaporator technology when it comes to a system like I have described? Ay reason not to use a plate in the fridge? Would that cause the stuff in the fridge to freeze?
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Old 25-08-2015, 15:36   #2
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Re: Are holding plates "old" technology?

Holding plates were/are used when you have large compressor capacity and need to store the energy like engine drive or in my case a 1/2 HP DC system.

Run a large compressor for a short time and store the energy in a holding pate, or run a smaller compressor for longer time with a roll bond evaporator plate. I can't see the advantage of a holding plate and a small Danfoss style compressor that is going to run a lot anyway unless the boxes are larger than the Danfoss can handle.

Maybe Richard Kholman will step in here and comment also.
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Old 25-08-2015, 15:48   #3
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Re: Are holding plates "old" technology?

First off, insulation is very important. You mention yours is 27 years old, and it sounds like you are considering a major rebuild.

Technautics has plans for a combined freezer/refrigerator box. The holding plate is in the freezer compartment and adjustable openings allow communication between the two compartments to keep the fridge cold. Perhaps something like that will work for you.

On Orontes II, we have two separate units, both cooled by Technautics Cool Blues. The holding plates work great for us. Whether it is old or new technology was not a concern for me. I was impressed by the small size and energy-efficient design.

Good luck with your design. Cheers!

Steve
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Old 25-08-2015, 16:05   #4
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Re: Are holding plates "old" technology?

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Originally Posted by steve77 View Post
First off, insulation is very important. You mention yours is 27 years old, and it sounds like you are considering a major rebuild.

Technautics has plans for a combined freezer/refrigerator box. The holding plate is in the freezer compartment and adjustable openings allow communication between the two compartments to keep the fridge cold. Perhaps something like that will work for you.

On Orontes II, we have two separate units, both cooled by Technautics Cool Blues. The holding plates work great for us. Whether it is old or new technology was not a concern for me. I was impressed by the small size and energy-efficient design.

Good luck with your design. Cheers!

Steve

I have some questions for you... if you do not mind...

1) Where do you cruise?

2) What is the size of your boxes?

3) How many amp/hrs do you find are consumed?
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Old 25-08-2015, 16:34   #5
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Re: Are holding plates "old" technology?

We lived aboard in Kemah, Texas for a year while finalizing our cruising refit. We are currently in Terceria, Azores. So a year in a hot climate and now in a very temperate one. The units are installed separately, with the one for the refrigerator in the salon and the one for the freezer outside in the cockpit locker. This means in Texas, with the air conditioner running, the refrigeration unit had nice 70 degree air to work with while the freezer unit had 95 degree ambient air. The freezer ran continuously on hot days and the freezer did not get as cold as it does now. Since then I have added 5 inches of insulation to the bottom of the freezer box, so it decreased the volume of the box while adding insulation. So the freezer is much colder as a result of the cooler ambient air, the reduced volume, and the increased insulation in the bottom of the box. I can't quantify which of those factors made the biggest difference.

The fridge is 20"x19"x21" The freezer is larger - 35"x19"x21".

I do not have a good estimate of Amp-hours consumed on a daily basis by the two units. I will say that at anchor our 540 Watts of solar power absolutely meet our electrical needs for the freezer, fridge, lights, fans, etc.

The freezer runs a lot, maybe 20 hours a day to keep the box at 16 degrees average. It's 0 at the bottom and warmer near the top. We use an insulated blanket on top of the food to help minimize air circulation. I should mention that this box does not have the best insulation, even with the addition of insulation to the bottom. It is on my long-term wish list to rebuild and reinsulate this box.

The refrigerator runs a lot less often, maybe 4-6 hours per day. These are estimates.

Have you looked at an old book called "The Perfect Box:39 Ways to Improve Your Boat's Ice Box"? It has a lot of good info on insulating the box to minimize running of the refrigeration units.

Hope this helps!

Steve
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Old 26-08-2015, 08:26   #6
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Re: Are holding plates "old" technology?

Just doing that myself. Switching from a danforth style refer/freezer to a new system. The old was a 12 volt system with 2 12v compressors one for each box and it seemed to run forever on the freezer side while running about 20 minutes per hour on the refer side.I have decided to go to an engine driven/110v compressor driven setup. Cost a bit more but should draw no 12 v and work without running too long even in 110v mode. The engine drive/110v will keep all extremely cold and is a custom from scratch setup.
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Old 26-08-2015, 08:29   #7
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Re: Are holding plates "old" technology?

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Originally Posted by captaindanger70 View Post
Just doing that myself. Switching from a danforth style refer/freezer to a new system. The old was a 12 volt system with 2 12v compressors one for each box and it seemed to run forever on the freezer side while running about 20 minutes per hour on the refer side.I have decided to go to an engine driven/110v compressor driven setup. Cost a bit more but should draw no 12 v and work without running too long even in 110v mode. The engine drive/110v will keep all extremely cold and is a custom from scratch setup.
Although I don't intend on going that route, I think it would be useful to the forum if you could document that design and the build out process on another thread!
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Old 26-08-2015, 08:50   #8
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Re: Are holding plates "old" technology?

Your insulation will make a dramatic difference in WHATEVER modus you use. After that, the gasketing, both to prevent heat gain and for humidity gain (requiring defrosting).

Even current insulation will have a finite life, though better than what you have now. If it's 27 years old, nearly certainly there's too little, and it's degassed to the point where it's nearly useless.

We wound up cutting out our monster 19CF icebox (AC and engine holding plates) and starting over. You can see that in the earliest of my gallery sets, scattered through the other stuff we were doing. Our current reefer/freezer has a spillover fan and is about 6.5/3.5CF, respectively, with 6" of epoxy encapsulated extruded polystyrene (doesn't absorb water, already) in all (including the doors) but the top, which is 4" - and the doors are double gasketed.

My current angst with SeaFrost aside, our system works a treat. The SF system defrosts very quickly, as it's entirely SS clad. I can't imagine how long it would take to defrost a holding plate (you have to heat the eutectic until it melts the ice off the back), let alone chill it again once you've heated it; our plates (there are three evaporator plates which look like thin holding plates) can be defrosted very quickly, and recover from the high-80s ambient temperature to freezing again in about a half hour.

Our previous system, which used about half the energy to make more cold, was a Frigoboat keel-cooled system, with their largest SS front-ed evaporator plate; that saga is available in other threads - I could not replace it without destroying our box, so the tech that the US distributor for Frigoboat referred used SeaFrost. It works, and works well, but at double the cost in electrons of the FB.

YMMV, but I prefer a much closer control on temperatures than a holding plate would allow. The hysteresis on the plate in the freezer is the factory recommended 6.5, but the reefer is 2, both with Carel electronic thermostats, the freezer being a smart controller as well.

My thoughts only ☺
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Old 26-08-2015, 09:38   #9
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Re: Are holding plates "old" technology?

I, too, am in the middle of a build and am looking closely at refrigeration. Due to the size of my boat and the location of the units, I can get optimal insulation for the 2 units. I want to have 2 freezers that can also double as refrigerators. Both units will have R30 insulation and each will be serviced by separate compressors. Both will use evaporator plates rather than holding plates as I will be working off solar/wind/water generation rather than engine/generator power. The size of the units are the sticking point. I think I can get up to 5 cubic feet of space in each while maintaining a decent freezing temp in the tropics - am hoping I can do this without resorting to using water cooling. I think that may be difficult. I don't want a circulating system if I do - would rather have a keel cooler. I wish the Adler Barbour system had such but they don't. I also have to make sure I have sufficient generating power to keep the batteries happy. On a ketch rigged cutter that is proving to be somewhat of a Gordian knot.

I bought Kollman's book and am reading it again. I have tried to join the forum but haven't been approved. I suspect this may be a busy time for him. He is a big supporter of air cooling but the tropics may just be too much for my application.

Kollman has opined that the development of the variable speed constant running Danfoss compressors make the evaporator plate much more efficient and a viable option to holding plates. It is just a matter of how you are powering your compressor. If you are running off your propulsion motor or an on board dedicated generator, the holding plate is the best bet. For solar and wind power, it seems the evaporator plate is a good fit.

I am just learning all this stuff - I could not be confused with someone who knows what he is doing.

Thank you, zboss, for starting this. Sorry I can't offer much info but am keen on reading what you and others are considering.

Daniel McNeil
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Old 26-08-2015, 11:19   #10
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Re: Are holding plates "old" technology?

Where people go wrong in trying to compare holding plate eutectic vs evaporation plate technology for the tropics isn’t with the type of evaporator, but in the compressor/condensing unit design and the differences that let one operate better in hotter ambient temps. This is getting down into the weeds of technical details, but here we go.

An often overlooked benefit with holding plates using air only cooling is the size of the condensing radiator they allow you to use (larger), thus they can operate in hotter environments with air cooling only compared to critical charge/evaporation systems. When we say we can operate up to 120 degs F without losing compressor efficiency where the typical AB Cold machine requires water cooling once the temps get above 90 degs F to not lose efficiency, that isn’t just some BS marketing thing, but rather a physical property of the differences in how a holding plate system with a thermally adjusting expansion valve (TXV) and a critical charge evaporation system work. I’ll try to explain.

Evaporation units with the thin rolled aluminum plates are known as critical charge systems. When this type of system is up and running there is a balance of refrigerant being pushed against the set critical orifice to create the pressure drop and the suction side of the compressor pump. Too much or too little refrigerant (like ounces and fraction of ounces) will throw the system out of balance and cause it to not function properly. This means the internal volume of the refrigeration loop must be matched with the volume charge. You can’t just add in a much larger condensing unit (radiator to dissipate the heat from the refrigerant) because that will screw up the volume/charge of the system. These type of systems have a typical volume charge of refrigerant of like 3-5ounces. Its why all of these systems come with a set one length of copper lines, because you can’t screw up the volume of the refrigeration loop.

Holding plate systems with TXVs are different. They incorporate a large receiver/drier unit downstream of the compressor where the full charge of refrigerant can be stored (in our case 24Oz) until the TXV throttles open and calls for the refrigerant to flow into the holding plate. The compressor isn’t pushing against a fixed orifice just trickling in “cold” but the TXV is measuring the outlet temp of the holding plate refrigerant gas and throttling in the right amount of refrigerant needed based on the heat load. The rest of the refrigerant is just stored in the large dryer/receiver. This design difference takes away the “critical charge” nature of the system and lets us oversize the condensing unit rather dramatically. A larger condensing unit can get rig of more heat in hotter ambient conditions. If you set the standard air cooled unit next to ours and compare condenser size, it’s obvious right off the bat. The air cooled units we make for the US Military that they use in mobile food boxes (the same CoolBlue 12v unit painted army green) passed the millspec temp rating for 135-deg ambient temps.

Because a eutectic solution holding plate and evaporation place can use the exact same compressor, people assume the “magic” of the CoolBlue is just the holding plate rather than the entire system design.

You can also look at the running data. A holding plate system can run 4-8 times off/on in a 24hr period to keep the box cool, while a evaporation unit has up to 177 on/off runs. For hit the same temps. You can see this real life data here: CoolBlue Boat Refrigeration Units | Cruise RO Water & Power

Now which unit will last longer? The one starting up 150-177 times per day or the one starting up 4-8 times per day? Which unit wastes all that start-up energy of building up head pressures?

Another myth about holding plate vs evaporation plate is the temp window spread and thinking holding plates have a wider spread. That WAS and IS true for engine driven systems or 120V AC systems that you manually turn on and off. But for units controlled with a thermostat, just decrease the hysteresis set point and your holding plate system will cycle on and off more frequently (for shorter periods of time), but you won’t have a big difference in temp swings. This myth is just a left over artifact of the old days of engine driven and 120v AC manually turned on a compressor that gets repeated as “fact”. Just check out the data in the graph above comparing a AB super cold machine to a CoolBlue unit. The data was collected independently by Catalina Yachts when they are testing the CoolBlue as an upgrade option for their boats.

Now what’s the negative of a eutectic holding plate system?
1. They cost more because of the extra parts and construction and we are not buying rolled aluminum evaporators by the cargo container from China for $47ea. We are actually building the entire unit in San Diego paying American wages…..uggg….yes…people still do that these days.
2. They have a slower start-up time because you are not just cooling down the Box, but also freezing down the eutectic solution.
3. They do have a slower response time when loading food items.

[[[In case anyone doesn't know, I am the owner of Technautics/CoolBlue for full disclosure. But I also try to be honest about the positives and negatives of what I make and sell. Because as a cruiser myself, I'm sharing the anchorages with clients so blowing smoke up someones ass to make a sale isn't how I operate.]]]
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Old 26-08-2015, 12:21   #11
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Re: Are holding plates "old" technology?

We are in the tropics and used to have the Glacier Bay Mark II holding plate system (24 V) for our fridge and freezer. It was a complicated nightmare with many moving parts and valves and the time I - and others at $100 an hour - had to spend on it just to keep it happy was not worth it.

Eventually, in Tahiti in sweaty desperation I ripped it out, dumped it overboard and installed an evaporator plate system with two BD-50 compressors. The difference:

1) Zero maintenance!
2) Silent operation
3) No vast temperature swings
4) More room in fridge and freezer

I took the copper coils and put them in my large water tank so now I have no water pump that draws power to worry about. I can also remove two more holes in the hull.

I am not sure about power consumption as we have been living with the system for just a couple of months now and because it is SILENT (did I mention that?) I don't really know if it is on or not unless I keep checking the battery monitor.

One caveat, Rich (Third Day) KNOWS what he's talking about and I DON'T. I am only telling you our experience so far and we have been very happy with it.

Cheers.

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Old 26-08-2015, 12:47   #12
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Re: Are holding plates "old" technology?

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We are in the tropics and used to have the Glacier Bay Mark II holding plate system (24 V) for our fridge and freezer. It was a complicated nightmare with many moving parts and valves and the time I - and others at $100 an hour - had to spend on it just to keep it happy was not worth it.

I think I would have done the same thing with that Glacier Bay my friend! Evaporation plates with BD50s or Eskimos bringing you ice would have been better than what you had. Those systems gave a black eye to the world of Holding Plates for sure and the bottom of the Ocean was where it belonged...ha ha ah
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Old 26-08-2015, 13:09   #13
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Re: Are holding plates "old" technology?

A Danfoss with an evaporator plate may well run nearly continuously in the tropics, so it isn't starting up and shutting down as often, if I have read that right. The compressor can slow down and act quite efficiently with the variable speed capacity. I have heard those compressors are quite robust, despite their tiny appearance. Less moving parts (capillary tubes instead of valves) and all that.

Running a holding plate with solar power and batteries is discouraged from what I have read. The convenience is that folks only need to run their generator in the am and pm to recharge the plate. I won't have a generator and will not use my propulsion motor for that purpose.

I've got a lot of learning to do. And a lot of thinking.
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Old 26-08-2015, 13:39   #14
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Re: Are holding plates "old" technology?

Zboss, thanks for starting this thread. I'm in the same position you are (same boat, same age about...) but with a lot of other priorities to deal with on the boat before I tackle the fridge/freezer
Will be following this thread with interest, and hope to hear how you go about tearing out the old and rebuilding

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Old 26-08-2015, 13:45   #15
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Re: Are holding plates "old" technology?

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A Danfoss with an evaporator plate may well run nearly continuously in the tropics, so it isn't starting up and shutting down as often, if I have read that right. The compressor can slow down and act quite efficiently with the variable speed capacity. I have heard those compressors are quite robust, despite their tiny appearance. Less moving parts (capillary tubes instead of valves) and all that.

Running a holding plate with solar power and batteries is discouraged from what I have read. The convenience is that folks only need to run their generator in the am and pm to recharge the plate. I won't have a generator and will not use my propulsion motor for that purpose.

I've got a lot of learning to do. And a lot of thinking.
You may want to rethink the question of why. The reason a Danfoss/Evaporation system would run near continually in the tropics isn't a positive attribute or a plus. It is because it can't keep up with the heat load. So while it is quite common in poorly insulated boxes or when the unit is undersized for the application or when the air cooling just can't keep up with the ambient temps, as they say in Mexico, "es no bueno senior".

If the refrigeration unit can't keep up with the box heat load, you won't be running on a lower variable speed, but at a full 5Amp load. We spent 4 summers in the Sea of Cortez and saw first hand what 5A * 24hrs will do to a cruisers battery bank....not good.

The dock rumor of it being "discouraged" to run a 12v holding plate system from wind and solar just isn't true. Running just in the morning and evening manually, is the old school engine driven or 120v driven approach, which doesn't apply to the current designs with thermostat control. We have been building 12v holding plate systems for boats running exclusively off wind and solar out traveling the world now since the advent of the early 12v compressor units....I guess around 20yrs ago now.

Back in "the day" before the 12v compressors hit the market and proved their long term reliability Technautics built engine driven and 120v units exclusively and were OEM equipment on many of the big name cruising boats. But we haven't built an engine driven unit in over 13yrs...we just send them to Sea Frost and let Clive either try to talk them out of it or sell them one (Sorry Clive).
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