[UnionPacific]

I am coming up on the final part to our refit. One item we really want to have is a deep freezer able to hold meat for a long time at very low temp.
The box is about 5cu ft
I think I need a BD50 and a full size plate, would a holdover plate get cold enough for deep freezing?
I am also looking at a dc5000 with twin hold over plates.
Not sure exactly what I need, but the freezer is not well insulated, and will receive one more layer inside, 1" construction foam, before the plate goes in.

 

[RichH]

would a holdover plate get cold enough for deep freezing?

Generally NO! Holding plates using eutectic salts typically optimize out at 20-26°F which is too warm for 'deep freezing'. For deep freezing ('hard' ice cream) you need close to 0 to 5°F and that is best done with a standard plate and the expansion valve trimmed to yield that 0-5°F temperature hold. IMO - holding plates take up too much interior volume for the job you expect them to do; better to deep freeze and keep the box filled with deep frozen items (but with lots of air circulation spacing).
With deep freezing, your energy drain goes way up, especially if your box is not super-insulated and air tight.

 

[Bene505]

On our Beneteau 50, we started with the regular freezer and then carefully fitted 2" thick pink foam on the inside. The inside foam is very snug and on all 6 sides. That's the top with a pink foam hatch, left, right, front, back, and bottom with extra thick foam that started out as a block and was hot-wire cut against a template. (Picture-hanging wire connected to a car battery, suspended across two uprights in place over a smooth flat surface.)

Our BD50 uses R-135a as the refrigerant. I ran the freezer non-stop for days and got it down to about 5 degrees Fahrenheit. I think there is a limit to what R-135a can do. That was during 75 degree days.

The key to any freezer installation is insulation. Heat going into our freezers is the "other" leak on our boats.

If I was starting from scratch and I wanted really cold temps, I'd use a giant thermos, called a dewar, the kind they use for cryogenic freezing. I'd get one with as wide a month as possible. The vacuum between the inside and outside surfaces conducts no heat, the only heat transfer is by radiation or the minimal conduction where the inside and outside surfaces meet at the opening.

True story, I had a regular thermos filled with liquid nitrogen many years ago in school. It lasted days in that regular thermos. Nothing beats a vacuum as insulation, and why not use something designed to have minimal loss.

The key to any freezer installation is insulation.

10LD Liquid Nitrogen Dewar | LD10 Liquid Nitrogen Dewar | Taylor Wharton 10LD Dewar

And check eBay.

Regards,
Brad

The key to any freezer installation is insulation.

 

[newhaul]

We have a cool blue system from rich at technautics and turned up to 7 we are able to hold our 3 cf freezer at 5 to 10 deg above zero f that's with a 7 cf spillover fridg at 25 to 30 deg so I would assume that we could hold closer to zero with just a dedicated freezer using the 134 and a db50 compressor. For colder than that you may have to go to a colder freon like 404 in the system. Rich or tellie over on the other cruiser forum will be able to give you good advise on the subject.

 

[MarkofSeaLife]

The most important thing about freezers is to understand that 0 F was stipulated not for freezing necessity but for cenvenience of the number.
In Celcius it makes little sense -18, but there you go.

(Remember I am in the tropics. Ambient temp is about 30 C)

In a boat freezer temp is vitally important because it will be the higest daily power user and even a change of 5 degrees F or C will change your battery load a lot.

In Celcius (I let you do the conversion)
-18 you dont need
-15 all ice cream stays rock hard
-10 ice cream may be a little soft but its still frozen. It will remain fresh while you scoff is down, probably afew months.
Meat is rock hard and will remain good for a virtually unlimited time
-5 too warm for ice cream. Meat is rock hard and OK for 3 to 6 months
-1 I think I remember reading meat does not really spoil for many weeks.

So my freezer is set at -10. Each degree below -10 takes a noticable and considerable extra compressor time. I havent had mine below -13 as it runs 24 hours per day with no effect. -10 runs about 15 mins per hour.

 

[miatapaul]

I think if you have any hope of keeping it freezer cold without pulling a ton of amps, then you need at least 6 inches of quality insulation. I think Defender sells pour in place two part foam that will fill in large gaps around the existing box.

 

[Bene505]

I should have added that the same compressor also runs the refrigerant through a large, adjacent fridge. So there are two cold plates in the overall circuit.

Regards,
Brad

 

[svHyLyte]

Our freezer of 3.75CF is heavily insulated with at least 4" of foam on all sides and an extra layer of foam on the bottom. The evaporator plate is a U-Shaped affair that wraps around 3 sides powered by a SeaFrost cooling unit. For travel we stock the freezer with pre-frozen food products and serving size pre-made meals, stacked in the order they will be used. Most important (at least for our daughter when she was a child) is/was a supply of Ice-Cream bars and a tub of chocolate/strawberry/vanilla Ice Cream (with waffle cones in the pantry). Even in the heat of southwest Florida summers our freezer unit runs only about 8 hours at day (and less once the stock of ice-cream bars was depleted due to fewer openings!). Because of the freezer, we became very popular with my daughters' friends who referred to us as "the Ice Cream Boat".

For what its worth, I think the key to our system is firstly the amount of insulation and secondly, the relatively large size of the evaporator plate compared to the box itself.

FWIW...

 

[SVAuspicious]

Not sure exactly what I need, but the freezer is not well insulated, and will receive one more layer inside, 1" construction foam, before the plate goes in.

Advice above is pretty good. I'll pile on and repeat the important part: insulation is the first priority unless you plan on being plugged in all the time. Take the furniture apart and start over if you need to.

 

[deniseO30]

I'd only add that the lid as important as the box insulation. it needs to be air tight as possible and insulated also. Box insulation should be most heavy on the bottom. a drain should be "plugable" in the least, since cold air will drop out of the drain tube. 2-3" of foam is quite effective.

R units don't "work harder" in badly insulated space, they just run longer. amp ratings are usually at full load, which is not often reached even in the tropics.

 

[UnionPacific]

So now I have a mixed opinion from you guys.
One of you is using holdover the other not.
The used system I am looking at has 3 holdover plates, they had it setup for two in the freezer, and one in a fridge. Can I get to -15c(5F) with two holding plates and the right brine solution? I may make the area under one of the sinks a fridge.
The compressor is a watercooled DC5000, so plenty big.

 

[Don L]

To me a holding plate only makes sense if you are battery charging via your engine or a generator. Because you run the freezer/frig at the same time as you battery charge. But you aren't ever going to really have good temperature control that way.

I maintain my freezer at around 20F and everything is rock hard. It uses around 60AH/day for the most part.

 

[newhaul]

We have a holding plate system and we have the freezer at 20°f and the fridge at 38°f
With a single holding plate with the freezer solution and an air cooled db50 compressor we use about 20 ah to maintain those temps and solid meat and hard ice cream we also charge with solar not the Engine (our usage data is not complete just installed new system in Dec so with cool temps and 50 °f water we will have better numbers after this summers cruising ). I don't expect the usage to change much. Here in the pnw the water doesn't get much warmer than that the low 60's and air temps are usually in the mid 70's in the summer.

 

[Bene505]

Our boat came with an engine driven system with holding plates. I converted it to an electric compressor, so we really don't need the holing plates but they were there already.

However, we cool during the day using solar to a lower set of temparatures, and not drain the batteries as much at night, so the holding plates fulfill their purpose.

Regards,
Brad

 

[hellosailor]

Brad-
The cryo flasks tend tend to be expensive with narrow necks to limit gas loss. But perhaps you noticed, they are also all cylinders because a hard vacuum really would collapse the walls of anything else? So you're kinda stuck with cylinders (big waste of space in a galley) otherwise you could just weld up stainless plate and pull a hard vacuum with an a/c vacuum pump, couldn't you?
I think aerogel was supposed to fill this need (almost as good as a vacuum insulation) but it was found to degrade after time?