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Old 28-04-2015, 14:36   #16
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Re: Make a freezer in existing fridge?

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Originally Posted by malbert73 View Post
That's great advice. Many thanks for the quick reply. This will be my spring project. Quick question what kind of glycol do I use? And should I use distilled water?
In a perfect world, you would use a food grade Propyele Glycol and Distilled water. But in the real world you can use just plain old Automotive AntiFreeze cut with plain tap water. We have done testing on different brands, food grade vs car antifreeze and found the results to be within the margin of error for the testing.

Here's what's important:
Different AntiFreeze brands of compositions can have different freezing points. So read the back of the label and follow the directions to hit the proper freezing temperatures. For a Freezer plate you want Zero Degs F and for a Refrigerator plate you want 25-degs F. For the Glycol we use that turns into a 1/3 to 2/3 for a freezer plate or 10% to 90% for a refrigerator plate (Glycol to Water).

A client I just spoke to on the phone reminds me of a good thing to mention here. Your thermostat sensor needs to be attached to your holding plate and not flapping around in the air measuring the box temp. We solder on a 1/4 copper tube to the side of the holding plate so you can side the sensing tip of the thermostat into that tube that way it's firmly attached. If you don't have a 1/4" copper tube attached to your plate, it's a piece of cake to attach one with a little JB Weld and what boat doesn't have a little JB Weld aboard? Mount the tube 1/2 way up on the side of the plate for a good reading.

Good luck and feel free to ping me if you need help or advice.
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Old 28-04-2015, 15:43   #17
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Re: Make a freezer in existing fridge?

Interesting and informative information string, I enjoy the blend of experience and academic information being shared. I do think it is unfortunate that we’ve distorted the true definition of eutectic. A bucket of ice water will be 32 degrees, absorbing 144 BTU’s per pound, and the surrounding melt holds that temperature until the last cube melts. When you add salt you drop that eutectic point. This is the most efficient approach in a holdover plate design but makes it more expensive, (i.e. Glacier Bay, Dole, Grunert, Frigoboat), because you cannot mix metals in a brine solution. The tubing must be the same grade stainless as the plate. Using a glycol solution is a way to reduce costs (i.e. Sea Frost, Adler Barber, Technautics, Technicold), but the solution does not remain temperature stable while absorbing BTU’s. It is not a eutectic. Glycol plates work well and are more affordable, but they must be larger (less water per volume) and pulled to a sufficiently low temperature as to not breach safe storage temperature during absorption.
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Old 28-04-2015, 15:53   #18
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Re: Make a freezer in existing fridge?

Hey first welcome to Cruisers Forum a better collection of crazies and nuts all loving boats you won't find!

Now on topic....

Oh absolutely...a glycol solution is not a true Eutectic solution.

But it also does have pretty good Eutectic properties, so the industry calls it the Eutectic solution and moves on because at the end of the day what matters? Performance vs Cost.

Would a brine salty corrosive solution give you a better Eutectic performance? Well Yes it would...but at what costs and what does that really mean to the Cruisers? Answer....nut much. We have testing comparing brine Eutectic solutions to the glycol we use (you can find similar info in an online search) and at the end of the day the added efficiency difference isn't big enough to justify the nastiness in using the salty brine.

This gets into the technical weeks that a lot of folks don't care about and is often where the internet experts without any real world experience go horribly wrong in trying to build their own systems. They take the data and pure analytical science without the real world data thrown in and Sha-Zam...off they go on a while goose chase for some salty brine because everyone knows that salty brine is better than glycol right? Well almost until his holding plate looks like Swiss Cheese somewhere south of the border.
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Old 28-04-2015, 15:55   #19
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Re: Make a freezer in existing fridge?

In my experience, allowing the air in the freezer to mix with that in the fridge (spillover system) will increase the icing in the freezer. If you make the partition airtight, you can use a simple thermostatic fan and a heat exchanger to regulate the fridge temp automatically, and avoid this issue. Still allows you to run both fridge and freezer from the one refrigeration unit. This is what I have in my boat, and it works great!
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Old 28-04-2015, 16:12   #20
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Re: Make a freezer in existing fridge?

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In my experience, allowing the air in the freezer to mix with that in the fridge (spillover system) will increase the icing in the freezer. If you make the partition airtight, you can use a simple thermostatic fan and a heat exchanger to regulate the fridge temp automatically, and avoid this issue. Still allows you to run both fridge and freezer from the one refrigeration unit. This is what I have in my boat, and it works great!
There is always more than one way to skin a cat, but after 47 yrs of building these systems our mantra is "simplicity....KISS...Keep things as simple as possible." A simple thermostatic fan and heat exchanger can work for sure, but at what added cost, complexity, and maintenance?

What happens when the thermostat or fan dies?
Do you lose your refrigerator box contents?

A hole in the bottom of the divider with a flapper valve to allow and regulate cold air flowing from the freezer to the refrigerator along with an air gap on the top of the divider for the warm air to go back to the freezer doesn't use any power, has no electronics to fail and something cruisers like....it free.

The approach of not mixing refrigerator and freezer air together would lower but not eliminate the freezer plate frosting, so at the end of the day the question becomes how much does it lower the frequency of scraping the plate vs the work/cost of not mixing the air.
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Old 28-04-2015, 16:38   #21
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Re: Make a freezer in existing fridge?

We have many successful spillover systems that have no air transfer between the freezer and refrig compartments, but the process is a bit empirical. You isolate the freezer compartment around the evaporator or holdover plate by building a low density PVC enclosure with access through countertop lid. You stage the addition layers of 1/4" PVC panel until you have sufficiently retarded the influence of the freezer on the refrigerator temperature desired. You can then make minor seasonal adjustments to the influence on the refrigerator through a means of adjusting the thickness of one side (i.e. slide over panel that can incrementally double thickness). The refrigerators tendency to stratify the coldest air can be controlled through a small internal mixing fan triggered by a thermostat sensing the upper portion of the box. Needless to say, there are many boxes whose internal shape does not make this approach practical.
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Old 28-04-2015, 16:54   #22
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Re: Make a freezer in existing fridge?

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The refrigerators tendency to stratify the coldest air can be controlled through a small internal mixing fan triggered by a thermostat sensing the upper portion of the box..
Bingo...that's why setting up the natural air convection with cold air flowing through the divider at the bottom and then flowing back to the freezer at the top is such a good way to go...it gives you the air movement you need to keep temperature stratification down to a minimum without adding anything else to the box. It won't get rid of it entirely due to the laws of physics...but using the laws to your advantage can sure be helpful. On large refrigerator boxes, or ones that the clients jam pack with stuff like they will never see a fresh veggie market again adding a thermostat/fan to suck air from the bottom of the box and spray it around can help.
Something like this is cheap...easy and low power draw if you have it turn on when the compressor is running

http://www.cruiserowaterandpower.com...5-27-2013_.pdf

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We have many successful....
With your 3rd post....how about a little introduction.
It appears you are in the Marine Refrigeration Biz...so Welcome, what company or product line do you represent? That way we know a little about you and your background.

Welcome again...we can always use more technical folks on the discussion forum...the more point of views the better!
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Old 28-04-2015, 17:22   #23
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Re: Make a freezer in existing fridge?

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Originally Posted by SV THIRD DAY View Post
Bingo...that's why setting up the natural air convection with cold air flowing through the divider at the bottom and then flowing back to the freezer at the top is such a good way to go...it gives you the air movement you need to keep temperature stratification down to a minimum without adding anything else to the box. It won't get rid of it entirely due to the laws of physics...but using the laws to your advantage can sure be helpful. On large refrigerator boxes, or ones that the clients jam pack with stuff like they will never see a fresh veggie market again adding a thermostat/fan to suck air from the bottom of the box and spray it around can help.
Something like this is cheap...easy and low power draw if you have it turn on when the compressor is running

http://www.cruiserowaterandpower.com...5-27-2013_.pdf



With your 3rd post....how about a little introduction.
It appears you are in the Marine Refrigeration Biz...so Welcome, what company or product line do you represent? That way we know a little about you and your background.

Welcome again...we can always use more technical folks on the discussion forum...the more point of views the better!

I will look at the manual but I guess if I need a distribution fan I can wire it into the control board wherever the compressor power comes off


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Old 28-04-2015, 17:23   #24
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Re: Make a freezer in existing fridge?

I do have to say that the cool blue system as is makes a kick-ass fridge. Can't wait to add the freezer


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Old 28-04-2015, 17:36   #25
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Re: Make a freezer in existing fridge?

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I do have to say that the cool blue system as is makes a kick-ass fridge. Can't wait to add the freezer


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It works well, I have a 14 cu ft box and keep the freezer side at -5F and the fridge side at 27F, which apparently freezes lemonade, Ice tea and milk, but not Beer, so I keep the Wife's beverages on the shelf where it's slightly warmer and mine on the floor. You know your Beer is right when the bottle frosts over when you remove it.
Oddly enough the power useage is about the same as my box was with the Adler Barbor super cold machine, but it wouldn't really keep things cold, much less anything frozen. I thought I would at least double my energy consumption, but I haven't.


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Old 28-04-2015, 17:40   #26
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Re: Make a freezer in existing fridge?

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I will look at the manual but I guess if I need a distribution fan I can wire it into the control board wherever the compressor power comes off
There is a spare spade connector on the back of the electronic control module that energies when the compressor kicks on, so what I like to do is use a relay to pick up that 12v signal and then turn on your 12v fan. This way you don't run the risk of that axillary fan over-amping and kicking off the electronic controller along with it your Freezer/Refrigerator...or worst case damaging the controller.
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Old 28-04-2015, 17:44   #27
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Re: Make a freezer in existing fridge?

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a 14 cu ft box
Just for full technical disclosure...we upgraded a few things for this size of box from our standard system. The compressor and if I remember correctly...dual holding plates in the freezer.

Hard Ice Cream and frosty beer Rocks, you just made my day amigo, it's Beer time for me as well now!
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Old 28-04-2015, 18:20   #28
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Re: Make a freezer in existing fridge?

It's a BD-80 instead of a 50, and dual plates as I did not want to tear apart my Galley to re-insulate my box and do it "right" with better insulation, but even with the bigger compressor and dual cold plates, I'm getting and holding those temps with standard 27 yr old factory ice box.
But the kicker is after it cools down it' only pulling 5 amps when running, the same as the Super Cold machine.


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