Refrigeration: 12vdc Holding Plate vs Evaporator

[malbert73]

Hi everyone,

I am adding refrigeration to my boat, and will have a super insulated 6-7 cu foot box to refrigerate.

My main interest is low draw. I will be installing a keel cooler regardless of the system.

Initially, I was very interested in isotherm's smart 12 v holding plate which freezes up when voltage rises (ie engine running). Thought that would let most of the draw occur while I am motoring in and out of anchorages, which happens twice per day with my style of cruising.

Today at the boat show, the frigoboat guy did a nice job convincing me that an evaporator plate will be as efficient, but will regulate temp better and give me a built in freezer compartment to boot. He thought that it is more efficient to store the energy in batteries when engine runs, but. Have a low draw compressor run most of the day.

Any opinions?

[Overlord]

I have a new seafrost 12 BD unit with two stainless steel evaporator plates.Its the 2010 model with the pc board.Bought 2 thinking that one would not be enough as i have a spill over freezer/fridge.One works brilliantly on its own.
I am asking 1400 dollars

[svcambria]

Besides low draw you should consider the availability of parts and service for the system in the areas you wish to visit. Frequently the best system is the one which can be perpetuated...

Michael

[Celestialsailor]

Here is an excellent site for information. It will change your way of thinking about refrigeration. KollmannMarine Boat Refrigeration Specialist

[James S]

That sounds like a large refrigerator for daysails...are you constructing it new or is it existing?
If you go with the Frigoboat guys recomendation, will you be adding additional battery storage capacity? How does that jive with your current engine charging capacity?

[swagman]

I think the Frigo man was probably giving good advice, but I'm not sure you'd freeze down a 12vdc holding plate or even produce enough charge to power any decent sized fridge in maybe the hour a day you'd use and engine to anchor up.

We had 2 x evaporator plate fridges - aircooled compressors so not the most efficient- and our fridge consumption (well insultated but in warm climates) for 24 hours was around 150 ah.

To produce that another 50 ah for all the other needs we found one big and one small Solara panel helped supplement our engine running 2 hours each evening, and typically one hour each morning.

Three hours on the 120 ah alternator (which as 1500 revs probably produced 50 ah) did it for us. Plus we had enough batteries to store 850 ah produced whenever we wwere plugged in or had to motor, so had adequate back up if we ever fell short. Which does happen.

Hope this helps in your decision.
JOHN

[malbert73]

Originally Posted by James S

That sounds like a large refrigerator for daysails...are you constructing it new or is it existing?
If you go with the Frigoboat guys recomendation, will you be adding additional battery storage capacity? How does that jive with your current engine charging capacity?

Good comment which highlighted my unclear post. We often cruise for weeks, but usually coastal cruise rather than passages at this point. When we start doing passages again it may be in a bigger boat, or with this one re- outfitted.

My current box is over 8 cu feet, as it was designed to be an ice chest. I plan to reduce it significantly by adding insulation to the inside on top of the 4 inches it already has. Then I'll add new walls using shower surround panel material. I was also thinking of making a removable "foam block" for one side to shrink the box for when we go out for less time, which could be removed whenever we need more capacity for longer trips.

I agree with the Kallman PDF file, and just what the frigoboat guy told me: go with smaller compressor and run it as slow as possible for longer, rather than high speed more intermittently....

[Stu Jackson]

The basic differences is this:

If you ever want to leave your boat for a few days with the fridge running, the engine driven system will simply not work for you.

Nigel Calder did a good discussion about it in his Cruiser's Handbook.

Also, if you can stay on the hook for more than a day or more without running your engine, that's a nice plus.

[James S]

Originally Posted by Stu Jackson

The basic differences is this:

If you ever want to leave your boat for a few days with the fridge running, the engine driven system will simply not work for you.

Nigel Calder did a good discussion about it in his Cruiser's Handbook.

Also, if you can stay on the hook for more than a day or more without running your engine, that's a nice plus.

I have a holding plate that is run off a 12v compressor...its not necessary to have an engine driven compressor to use a holding plate.

[Richard Kollmann]

Most boaters do not understand the function of a holding plate there only purpose is to store surplus energy when it is available. Holding plates are also not as energy efficient as standard evaporators. Small Danfoss compressors do not normally produce surplus energy that could be stored in eutectic solution plates unless compressor runs many more hours per day wasting extra energy.
Unless a boat is equipped with alternative energy sources such as; solar, wind or water generator, use of eutectic holding plate with small 12 volt compressor condensing units is a waste of money and energy.

There are applications where refrigerator boxes are too large and temperature condition in lower latitudes are too warm for 12 volt systems, under these conditions a large compressor and eutectic plates are a must if refrigeration is important when not connected to shore power.

I designed several hundred holding plates when in that business and most were equipped with dual hybrid energy evaporator coils inside plate allowing use of both an engine driven condensing unit and either a small 12 volt unit or a 110 volt unit. I know SeaFrost still sells Hybrid systems.

[malbert73]

Originally Posted by Richard Kollmann

Most boaters do not understand the function of a holding plate there only purpose is to store surplus energy when it is available. Holding plates are also not as energy efficient as standard evaporators. Small Danfoss compressors do not normally produce surplus energy that could be stored in eutectic solution plates unless compressor runs many more hours per day wasting extra energy.
Unless a boat is equipped with alternative energy sources such as; solar, wind or water generator, use of eutectic holding plate with small 12 volt compressor condensing units is a waste of money and energy.

There are applications where refrigerator boxes are too large and temperature condition in lower latitudes are too warm for 12 volt systems, under these conditions a large compressor and eutectic plates are a must if refrigeration is important when not connected to shore power.

I designed several hundred holding plates when in that business and most were equipped with dual hybrid energy evaporator coils inside plate allowing use of both an engine driven condensing unit and either a small 12 volt unit or a 110 volt unit. I know SeaFrost still sells Hybrid systems.

I think my choice is made, based on what I have heard and read.
Make the box as small and energy efficient as possible.
Go with a 12V compressor with evaporator that will be shaped to give me a freezer compartment.
This not only will be efficient or more than holding plate, but also will hold a more constant fridge temp.
This lets the batteries store the excess energy when motoring.
Sail for a season and monitor amps and charging requirements, then design solar system as needed for supplemental energy.

Any opinions on isotherm vs frigoboat systems? I intend to use a "keel cooler" type system as sometimes we sail in pretty hot weather so air cooled may struggle. I can locate the keel cooler about 3-4 feet below waterline which should generally be in cooler water.

[svcambria]

Before you settle on Frigiboat or Isotherm consider cheap old reliable Adler Barbour water-cooled systems. I have added pump and relays to the A-B ColdMachine to use their built-in water-cooled condenser - you don't have to buy their addition- and plumbed it to a fresh water tank on board. Two advantages - no new through-hull, and it works when the boat is anywhere - even in the yard. And fresh water tank temperatures are pretty close to sea water temperatures.
Adler Barbour parts are easier to find - especially abroad...

Michael

[Richard Kollmann]

A properly installed Adler Barbour CU100 will out perform their water cooled model CU200 unless seawater temperature is maintained between 60 and 75 degrees.

[svcambria]

Originally Posted by Richard Kollmann

A properly installed Adler Barbour CU100 will out perform their water cooled model CU200 unless seawater temperature is maintained between 60 and 75 degrees.

Hmmm, that's interesting. Well, put the water pump on a separate circuit breaker so you can turn it off when you want (it is an additional option, not a necessity for the Super ColdMachine). Frigiboat and Isotherm do not suffer from a variety of sea temperatures?

Michael

[Celestialsailor]

This is all a great lesson for us Richard. I visit your site when ever I approach the boat refer topic. Certainly a small box with detail and thought to insulation is an economical way to go. I think that coupled with a change of life-style onboard will make this system very usable. Does the CU 100 have a BD35 or a BD50 compressor?