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Discussion Starter #1
Nowadays refrigeration on board is almost as common as a depth sounder, plotter or autopilot.
Boats may be made with a well insulated "ice box" which may even include an installed refrigeration system... or two boxes with one for a freezer. Many refer systems are installed by owners as an upgrade.

I am by no means an expert on refrigeration. I want this thread to be a discussion about options for refrigeration.

The refrigeration system should of course be informed by how the boat is used. Is it in a slip with available shore power, on a mooring with perhaps solar or wind or no alt power sources? Is the boat sailed off the grid and on ocean passages? How the boat is used, what sort of meals and beverages are consumed, the boat's architecture (and budget) will determine what sort of system is installed.

Refrigeration requires energy to remove heat... cool the box. Refrigerant systems use a gas which is compressed and becomes a very cold liquid. This liquid (refrigerant) is circulated to the box and absorbs heat from the box... or it might have air forced over it... circulating cold air into the box.... much as an AC circulates cold air into a warm room.

Some refrig systems use a "holdover plate" or cold plate which is located inside the box and acts like a block of ice. But as the "ice" is contained it does not melt. And the ice is not water ice but a eutectic solution which can make very very cold "ice". The cold compressed refrigerant as a liquid is circulated through the plate surrounded by the solution which freezes to ice well below 32° F (dry ice is well below water freezing temp at -100°F.

As the circulating refrigerant cools the liquid in the cold plate....the refrigerant's temps raise. it become a has and is returned to the compressor which it is compressed into a cold liquid and circulated back to the cold plate for more cooling. Depending on the characteristics of the cold plate liquid and the specs of the refrigerant will determine how cold the plate can become. So.... you could have a "refrigerator" temp cold plate... or a freezer temp. Oryou could run a freezer temp system a shorter time and not bring the all the eutectic to freezer temps... making it perform like a refrigerator.

The compressor is the energy hog of refrigeration systems. 12v systems use house batteries to run the compressor. They use a lot of amps and usually run on and off all day to maintain temps per thermostat demands. The other alternative to drive the compressor is to use a generator or engine with the compressor mounted and driven by belts much as the engine drives the alternator. Engine drive compressors do not use many amps at all... only what is needed to have a magnet pull a clutch to engage the compressor. With the magnet off... the compressor "free wheels" offers no loss of power to the engine nor uses any electricity at all. To operate an engine drive system the compressor is "engage" usually with a timer switch.... but a simple on off switch works too. With engine drive refrigeration the engine must be used. But how long it is used depends on the temp in the box which can thermostatically energize or cut the compressor.

The decision between 12v and engine drive might depend on access to shore power and constant battery charging.... or ample alternate charging sources such as solar and wind... and large batteries to store the electricity which will constantly draining all day and night. Engine drive only cools when the engine / compressor runs.

Of course when you run the engine you will likely be making hot water. Electric 12v heated hot water is not efficient. You will also be charging your batteries (as you cool your box) and can use an inverter to charge portable devices... laptops and phones... or operate 110v devices like tools and vacuums and blenders etc.

Boats which spend a lot of time in a slip with shore power will likely use 12v refrigeration. Boats on moorings will have to have large battery banks and alternate charging sources... including perhaps a genset.

Boats that move in and out of harbor/mooring fields and anchorage using their motor can use this time to cool the refrigerator or freezer. Since the plate temp is so cold... it is not necessary to cool it down multiple times in the day. But any time the engine runs the plate can be cooled down.

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I installed an engine drive 3 decades ago. It's a freezer temp system but used as a refrigerator. Plate is very cold and things touching the plate can freeze while food on the other side of the box is more like refer temps. You can make ice with a vertical tray placed against the cold plate. I run the compressor less than 1 hr a day. For offshore the box becomes a freezer and is packed with pre cooked frozen meals. As they are consumed... we replace them with foods that need to be refrigerated from a portable cooler... milk, juice, beer, cheese, cold cuts.... whatever.

Installation of a cold plate engine drive system requires mounting several components... which are connected with copper tubing... compressor, holdover plate, accumulator/receiver, flow thru condenser (plumbed to sea water). For sure it's not an easy install.... running copper and flare fittings, vacuuming and charging the system with refrigerant. Mounting the components is the easy part.

Engine drive is a smart choice for sailors who DO use their motors regularly/daily... as no large batteries are needed, alt charging sources and all that is associated with them. I see a lot of boats motoring and I assume these would be candidates for engine drive systems. But for those on shore powered docks much of the time... 12v might be the better choice as no need for alt sources and large batteries.
 

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1979 Morgan Out Island 41
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I'm running a 50 quart portable 110v/12v fridge right now. Middle of the summer set to 31 degrees. I have 400ah battery capacity and 200w of solar. I'm into float by noon each day. Only had one cloudy / rainy day that I did not get into float this summer. Looking at the charge times I should be able to get another 40 qt freezer and still get full charge each day.

Some of the off brand portables are getting inexpensive with good reviews. The one I have now is by ARB an australian off road company that was $900. I'm looking at a 40qt freezer (off brand) for $350.
 

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Today's 12V compressors really aren't the energy hogs they were the past. Quite efficient now, actually. The largest contributor to energy use will be the box insulation and design. Our last boat had a 6 cubic foot reefer spilling over to a 4 cubic foot freezer run off a single Danfoss BD50 compressor. The freezer was set to 5F and the reefer to 34F. This system used 50-70Ah/day depending on where we were located - 50Ah/day in the mid-Atlantic states, and 70Ah/day in Central America. This was full-time use.

BUT - the box was extremely well-insulated. The thinnest side (facing the coolest spot) had 6" of insulation, while the rest of the sides and top had 9". The bottom was 14" of insulation. They were top-opening.

Our current boat has a 4.6cf reefer, another 1.3cf reefer, and a 3.2cf freezer - all running on their own BD35 compressors. These are contained units like dorm fridges with front opening doors. The insulation is maybe 1-1.5" on the reefers and 2-2.5" on the freezer. Together, they use 150-200Ah/day, even though the actual current draw when the compressors are running is almost the same as that on our previous boat. They just run more often because of the poorer insulation.

Engine-driven compressors don't work for a lot of boats. Many don't have the engine space/mounting room, and the gas line runs can be very long if the engine isn't located next to the box. On ours, that would easily be a 50' tortuous run!

Mark
 

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Discussion Starter #4
Engine-driven compressors don't work for a lot of boats. Many don't have the engine space/mounting room, and the gas line runs can be very long if the engine isn't located next to the box. On ours, that would easily be a 50' tortuous run!

Mark
In a typical sailboat... the engine is fairly close to the galley. Mine is adjacent which is fairly typical. Tubing runs were short. Mounting a compressor CAN be a problem.... It's like having a second alternator. Mine is actually mounted to the bulkhead on the side of the engine "room"... with steel plates.

Retrofitting an OEM boat will likely involve inadequate insulation. Mine is no more than 3" top, bottom and sides.
 

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I really hated our engine drive system, even as a back up. It took up a lot of space in the engine room and heat exchanger, PVC and metal fittings, was always in the way. We also use the engine very little. The 110 vac unit is very powerful, and only needs to run about an hour a day, which we do with a gen set, using a fraction of the fuel the engine drive system did. Eventually, I'd like to add a couple (2 boxes) of 12 volt systems, using the 110vac system to bring everything down to temperature and the 12 vdc to maintain them.
However, to do it right, it would mean tearing apart the galley cabinetry and replacing the boxes and insulation, which are vintage 1980, a big, expensive job.
Or maybe I'll just go with lithium batteries and a charging system for them.
 

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I'm running a 50 quart portable 110v/12v fridge right now. Middle of the summer set to 31 degrees. I have 400ah battery capacity and 200w of solar. I'm into float by noon each day. Only had one cloudy / rainy day that I did not get into float this summer. Looking at the charge times I should be able to get another 40 qt freezer and still get full charge each day.

Some of the off brand portables are getting inexpensive with good reviews. The one I have now is by ARB an australian off road company that was $900. I'm looking at a 40qt freezer (off brand) for $350.
You might add another 200 watts if going with 2 fridge/freezer so that you can handle a few cloudy days.
I think these small portables have been figured out and lower priced units being reliable.
I ditched a hi$ engel, because of a micro leak nobody could find, and went with a 40 and a 20 qt cheaper models, for much less than 1 engel.
The 40 fridge seems to run about 25% of the time. The 20 freezer runs 100%
 

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1979 Morgan Out Island 41
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Yes, I plan on adding an additional 400w with a stern arch at some point to handle electronics underway (autopilot etc) and more usage of devices. Currently I live on the boat but am at work 45 hours a week so there isn't much usage other than the fridge. I do have a small generator that I can run if I really need to in order to top off the batteries.
 

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Discussion Starter #8
I really hated our engine drive system, even as a back up. It took up a lot of space in the engine room and heat exchanger, PVC and metal fittings, was always in the way. We also use the engine very little. The 110 vac unit is very powerful, and only needs to run about an hour a day, which we do with a gen set, using a fraction of the fuel the engine drive system did. Eventually, I'd like to add a couple (2 boxes) of 12 volt systems, using the 110vac system to bring everything down to temperature and the 12 vdc to maintain them.
However, to do it right, it would mean tearing apart the galley cabinetry and replacing the boxes and insulation, which are vintage 1980, a big, expensive job.
Or maybe I'll just go with lithium batteries and a charging system for them.
Interesting about the space.... Here are my engine room refer/freezer components - Compresser to the left of the flywheel.... flow thru is the black cylinder on the right in the 2nd pic
 

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Engine driven seems very inefficient with regards to carbon footprint

12 years ago my winter project was building a heavily insulated box . Our dimensions are similar to Marks.
It is cooled by a Super Cool machine Danfross 50 ( which I just replaced its board after 10 years) .
We use 40 ah per day in the dead of summer. It’s cold enough that we have 3 vertical ice cube trays and homemade sorbet in it. It’s air cooled . They are selling for less than $800 and can be self installed. It takes up very little space.

Yes we use shorepower and have an extra large bank of battery but with the proper solar array and 400 ah bank you could go almost indefinitely with it. We often go days without using our engine. We don’t need to turn the iron Genny on and waste it’s finite hours for refrigeration. I have as much issue with people doing this a running a Honda 2000 to recharge their batteries.
 

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A couple of seasons ago I replaced our old (~30 years) fridge/freezer with a new Nova Kool (LT201 RT4). It has made a world of difference for our cruising. The old compressor/cold plate drew a constant 7 amp, and almost never cycles. The new version runs at less than 4 amps, and cycles nicely.

My passive charging system (400 watts solar, 400 watt wind gen) easily keeps up with the draw now, except when we get prolonged heavy cloud days. I almost never have to run the big diesel or the gas generator now. It's been great!
 

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Interesting about the space.... Here are my engine room refer/freezer components - Compresser to the left of the flywheel.... flow thru is the black cylinder on the right in the 2nd pic
I can't tell the size of yours, but it seems about the same. Ours was right in front of the water pump of the Perkins in the middle of the engine room, standing vertically with hoses and copper tubing coming out. A bad installation for sure, but it was a pain. I kept the compressor mounting plate in case I want to add another alternator or hydraulic pump one day, but it is out of the way.
 

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Discussion Starter #12
Engine driven seems very inefficient with regards to carbon footprint

12 years ago my winter project was building a heavily insulated box . Our dimensions are similar to Marks.
It is cooled by a Super Cool machine Danfross 50 ( which I just replaced its board after 10 years) .
We use 40 ah per day in the dead of summer. It’s cold enough that we have 3 vertical ice cube trays and homemade sorbet in it. It’s air cooled . They are selling for less than $800 and can be self installed. It takes up very little space.

Yes we use shorepower and have an extra large bank of battery but with the proper solar array and 400 ah bank you could go almost indefinitely with it. We often go days without using our engine. We don’t need to turn the iron Genny on and waste it’s finite hours for refrigeration. I have as much issue with people doing this a running a Honda 2000 to recharge their batteries.
Carbon footprint?

Essentially I have a diminished footprint as far as energy consumption is concerned. I use my engine to leave and return to the mooring.... to go to and from the dock from the mooring. When motor is on I am:

refrigerating
charging my batteries
making hot water
making 110v electricity for whatever (charging phone)
using the windlass to raise or lower the anchor leaving / arriving at an anchorage.

My diesel fuel consumption is like 50 gallons l / season (including heating in shoulder season).

I don't run the engine solely to do any of the above.

My small solar array keeps my batts topped up when the sun shines and I am away from the boat.
 

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The 40 fridge seems to run about 25% of the time. The 20 freezer runs 100%
Does the freezer run so much for any reason (cheaper model, old, etc), or is this normal for them?

We are looking to add a 40-50qt portable freezer, but I would be disappointed if it ran 100%. That would be about another 50Ah/day and worse than our freezer that is twice as large.

Mark
 

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Its the lattitude/temp
I set it at 0, but just making ice usually..not freezing meat
May be able to set it higher..dunno

I did a longterm test with the engel before putting it on the boat. It would cycle when indoors but needed to run 100% when in the boat

If stores ever get sewing machines back in stock i plan to try a foam blanket
 

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Discussion Starter #15
How cold do you want your freezer to be?
 

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Carbon footprint?

Essentially I have a diminished footprint as far as energy consumption is concerned. I use my engine to leave and return to the mooring.... to go to and from the dock from the mooring. When motor is on I am:

refrigerating
charging my batteries
making hot water
making 110v electricity for whatever (charging phone)
using the windlass to raise or lower the anchor leaving / arriving at an anchorage.

My diesel fuel consumption is like 50 gallons l / season (including heating in shoulder season).

I don't run the engine solely to do any of the above.

My small solar array keeps my batts topped up when the sun shines and I am away from the boat.
How long do you have to run the engine to get the plate cold enough to last 3 days. Do you just idle it or run at a certain rpm

If you had solar and 12 volt you wouldn’t need to run the engine. That’s the carbon footprint.
 

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Discussion Starter #17
How long do you have to run the engine to get the plate cold enough to last 3 days
Last 3 days is not realistic. Temps will rise as we open the box and allow warm air in. It depends on how cold we bring the plate down.... we normally don't take it to super cold ice. But an hr will last almost 48 hrs.
Typically we bring a cooler bag with artificial ice cooled in freezer at home. We toss them into the box as well... so it's hard to tell the dynamics.

On a typical weekend we might arrive at the boat...stow, eat and go anchor near or leave in the AM. When we leave refer is running for about 45 min the time to prepare for sailing, get off the mooring and motor out to the a clear spot to raise the main and often motor sail in the channel to where we can actually sail... It's crowded there so motor is running in case I need to move somewhere fast to avoid a problem. It could be an hr of engine on. This will cool things way down. OJ next to the plate becomes a bit slurry, We repeat 1 hr engine use in the evening when we go in for anchoring. Cold is plenty cold. We don't need to go colder the next day... but we still motor out to raise our sail and clear out of the harbor and traffic.
 

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Sounds like engine cooling might be ideal for charter boats.
I remember having one on a boat in the virgins eons ago.
Wouldn't work for me now
Engine is often not fired for weeks..evens months
 

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Last 3 days is not realistic. Temps will rise as we open the box and allow warm air in. It depends on how cold we bring the plate down.... we normally don't take it to super cold ice. But an hr will last almost 48 hrs.
Typically we bring a cooler bag with artificial ice cooled in freezer at home. We toss them into the box as well... so it's hard to tell the dynamics.

On a typical weekend we might arrive at the boat...stow, eat and go anchor near or leave in the AM. When we leave refer is running for about 45 min the time to prepare for sailing, get off the mooring and motor out to the a clear spot to raise the main and often motor sail in the channel to where we can actually sail... It's crowded there so motor is running in case I need to move somewhere fast to avoid a problem. It could be an hr of engine on. This will cool things way down. OJ next to the plate becomes a bit slurry, We repeat 1 hr engine use in the evening when we go in for anchoring. Cold is plenty cold. We don't need to go colder the next day... but we still motor out to raise our sail and clear out of the harbor and traffic.
We don’t motor that much. Maybe 15 minutes and we are out on the Bay.
We leave the reefer on when we leave so drinks are cold and ice is made when we get there😀
 

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Discussion Starter #20
We don’t motor that much. Maybe 15 minutes and we are out on the Bay.
We leave the reefer on when we leave so drinks are cold and ice is made when we get there😀
As I wrote in the your options are driven by how you sail and so forth.

My experience has applied to the mooring locations I had in:

Deering Harbor
Stirling Harbor
Sag Harbor
Northport
Norwalk
Thimbles
City Island
2 Mile Harbor
Westport
Stamford
Oyster Bay
Huntington
Port Jeff
Inner Harbor at English Harbor'
Falmouth
Rodney Bay inner harbor
Marigot Bay St Lucia
Point a Pitre
Newport Harbor
Camden Harbor

and so on.

Sure there are locations and days when you can raise the sail at anchor and sail downwind right out the habor without needing the engine.

I find it prudent to have the engine on in all channels whether I am sailing or not.
 
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