120 vac or 12V Refridgeration

[lifeofreilly57]

I am currently totally refitting our boat, the deck is stripped, the engine is out and the interior is opened up for re-wiring. I'm in the process of drawing up the new schematics and ordering a new breaker panel, but I'm on the fence about which way to go with the refrigeration compressor.
The refrigeration system is currently 120VAC.
The boat has a 5KW generator, the water maker system is wired for 240vac from the generator.
I have two 8D house batteries and a separate starter battery and plan to add solar cells for additional charging capability.
We are setting up to do an extended 3-5 year cruise, sometimes through fairly remote areas.
I'm on the fence as to whether to change the compressor to a 12vdc compressor or stick with the 120vac compressor.
My reasoning is that running the watermaker will not be something I need to do twice daily, whereas I currently have to run the generator twice a day to keep the refrigeration sufficiently cold. With a 12V system, solar cells and enough battery capacity would I be able to keep the systems running and batteries topped up while on thew hook? We won't be staying in marinas very often, to help keep the cruising budget under control.
The boat has 150 gallons of diesel capacity.

[Jammer]

Originally Posted by lifeofreilly57

We are setting up to do an extended 3-5 year cruise, sometimes through fairly remote areas.
I'm on the fence as to whether to change the compressor to a 12vdc compressor or stick with the 120vac compressor.
My reasoning is that running the watermaker will not be something I need to do twice daily, whereas I currently have to run the generator twice a day to keep the refrigeration sufficiently cold.

You have an inverter, right? That should muddy the waters a little bit. But...

* If your refrigeration system is 12v, you will have refrigeration whether or not your generator (or inverter or both) are working. On the other hand, if your 12v system is not working, the refrigeration system will be the least of your problems.

* If your refrigeration system is 12v, you will not have to think about it very much. It will just work. On the other hand, if your refrigeration system is 120v, you will have to run the inverter or the generator from time to time.

* If you have an existing system that is 120v and is working to your satisfaction, you may be better off spending your money on an inverter is that is right-sized, and/or a spare inverter, rather than tearing up a working system. Modern inverters are very efficient. The "12vdc" compressors are essentially a 3-phase AC compressor with a fancy inverter running it, fwiw.

With a 12V system, solar cells and enough battery capacity would I be able to keep the systems running and batteries topped up while on thew hook? We won't be staying in marinas very often, to help keep the cruising budget under control.
The boat has 150 gallons of diesel capacity.

In general, yes. Your fridge has to be well insulated, and you have to have enough solar capacity, and there are potential difficulties during cloudy stretches where you'll have to run the diesel, but lots of people make it work.

[Cheechako]

I'd go 12v to avoid running the gen all the time.

[a64pilot]

If money is an issue and the 120V system is in good shape, I’d consider finding a pure sine wave inverter that is sized just to run the fridge, and run it off of the bank.
I say run a dedicated inverter cause my 2800 W inverter that can run anything but my big air conditioner cost 30W just being on and running nothing, a smaller one should have a lower draw from just being on.
However there is great convenience in always having AC power in the Boat to run the toaster, microwave, blender, TV etc. and 30 W is slightly less than 3 amps, so your call.

[lifeofreilly57]

The boat currently has a large inverter, but even the most efficient inverter is not that efficient.
I'm not as worried about the cost of converting to a 12V compressor but more interested in what kind of strain it puts on the battery bank and whats required to keep that battery bank charged.
Anyone out there currently running a 12vdc refrigeration system on the hook?
If so how's it working for you?

[a64pilot]

Just about everyone is running a 12V system, it’s the standard.
However tell us more about your fridge, what is it specifically?
We have a Mod that is running a 120V dorm fridge off of an inverter for thousands of dollars less than a 12V system, and is close to the same efficiency.
What is extremely important efficiency wise is insulation, it will make an inefficient compressor, efficient, and a very efficient compressor, inefficient, based on insulation, or lack there of.

I know that is obvious, just it can make more of a difference than you might think.

[S/V Illusion]

Originally Posted by lifeofreilly57

T
I'm not as worried about the cost of converting to a 12V compressor but more interested in what kind of strain it puts on the battery bank and whats required to keep that battery bank charged.
Anyone out there currently running a 12vdc refrigeration system on the

It's typical to see a 5 amp-hr draw when the compressor is running for the average size box, reasonably well insulated. There is no definitive range but that is a good approximation for planning purposes.

Depending on the duty cycle, that works out to be in the range of virtually any decent battery bank to accommodate.

In other words, this is a non-issue.

[lifeofreilly57]

Originally Posted by a64pilot

Just about everyone is running a 12V system, it’s the standard.
However tell us more about your fridge, what is it specifically?
We have a Mod that is running a 120V dorm fridge off of an inverter for thousands of dollars less than a 12V system, and is close to the same efficiency.
What is extremely important efficiency wise is insulation, it will make an inefficient compressor, efficient, and a very efficient compressor, inefficient, based on insulation, or lack there of.

I know that is obvious, just it can make more of a difference than you might think.

Currently it's built into the boat, it's about 25 cubic feet in volume, being bilt into the boats shape this is just a rough figure, I'll get an exact figure when I take more accurate measurements and run the numbers.
Right now it's one compartment and top loading. The insulation is about 3" thick, I haven't drilled into it yet to see what they used to insulation.
I am looking into sectioning off the interior of the compartment to make a freezer compartment.
It is currently a cold plate type refrigeration system. Running the compressor for one hour, twice daily usually keeps it about 38-40F inside during the summer months here when it's between 80-90F air temp. If I run it longer it drops below freezing.
If I decide to go ahead and divide up the compartment I'll add a front door to the regular refrigeration section but leave the freezer a top loading access door since it won't be accessed as often. Making the refrigerator side accessable with a front loading door will reduce the amount of time the door will need to be opened to get things in and out. Now it requires removing several baskets to get what you want.

[Terra Nova]

I built side by side refrigeration boxes into a Mapleleaf 50 and installed dual 12-volt Frigoboat keel-cooled systems which could operate both boxes as either refrigerators or freezers. During the summer, in Marina del Rey, the owner reported 2 amp/hour average draw, with both boxes running, 1 as reefer and 1 as freezer.

[a64pilot]

If it’s that big, your going to need two big cold plates.
I’d even go with a separate compressor for the fridge and freezer. I doubt there is a 12V single compressor that could handle that load.
Mine is 14 cu ft and takes every bit of a BD80 compressor, and I don’t think there is much bigger. There are some, but I doubt big enough for your needs.
Refrigerator and freezer use different fluids in the plates, the freezer plate is much colder of course.
What is normal is a spill over, which is an insulated wall in between the fridge section and freezer section, and you can make that as complex as you want, with just holes in the wall, to a fan with a thermostat to control fridge temp, freezer temp is controlled by thermostat.

However I think you will need two compressors, and if so I’d completely separate the two systems myself.

I’d guess you likely use 200 AH on a box that big, in the tropics, with what is likely old sprayed in foam insulation.
Get real good insulation and likely cut that number in half.
Most go with top opening under the theory that keeps the cold air in, where a door allows it to spill out, this is true, but air doesn’t hold a lot of heat, so it’s not as bad as you might think, just don’t sit there and browse the fridge wondering what you want to eat,

[Stu Jackson]

Originally Posted by lifeofreilly57

>>>>>>>>>>>>>>>>
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I have two 8D house batteries and a separate starter battery and plan to add solar cells for additional charging capability.>>>>>>>>>>>>>>>>>>>>>>>

In many of the electrical discussions here it has been pointed out that there are few, if any, 8D batteries that are truly deep cycle.

Have you confirmed that they are?

[Richard Kollmann]

For box or boxes over 10 cu ft you will never be happy with 12 volt refrigeration unless boat is operated only in cool seawater. Also forget running 1/2 hp or larger compressor powered by inverter I have done the inverter powered AC refrigerator design projects before when generators were removed from boats. Inverter then will always require a alternator running when refrigerator is running, even if house battery bank is fresh and new of 1000 amp-hrs. For back up AC power some boats carry a portable properly sized for refrigerator AC/DC generator. With the size of your boxes R-75 insulation also will not solve your problem either.

[Dougtiff]

Well to start with, it's crazy to have 25 cubic feet,my freezer is 6 c.f., and it holds enough frozen food for month's, the trick is to not pack meat with bones, like chicken and steak, it's amazing how much 6 c.f. can hold, also the other equation is temperature, to keep food frozen for very long times [large capacity],the temperature must be very low, so that means longer running times, today, unlike the 70'S when i was cruising one can pretty much find all the needs most anywhere, the same thing goes for refrigeration, you can only keep food refrigerated for a given time, as it will go bad, milk, lettuce, ect. has a limited storage time, my fridge is 12 c.f. and that works well for me. two seperate system's is the way to go, i would get rid of the hold-over plates and go with an evaporator, they come in large sizer and can be configured [bent] to fit the application, with two seperate system' if ong goes down, you have a back up.

[Cheechako]

Originally Posted by lifeofreilly57

Currently it's built into the boat, it's about 25 cubic feet in volume, being bilt into the boats shape this is just a rough figure, I'll get an exact figure when I take more accurate measurements and run the numbers.
Right now it's one compartment and top loading. The insulation is about 3" thick, I haven't drilled into it yet to see what they used to insulation.
I am looking into sectioning off the interior of the compartment to make a freezer compartment.
It is currently a cold plate type refrigeration system. Running the compressor for one hour, twice daily usually keeps it about 38-40F inside during the summer months here when it's between 80-90F air temp. If I run it longer it drops below freezing.
If I decide to go ahead and divide up the compartment I'll add a front door to the regular refrigeration section but leave the freezer a top loading access door since it won't be accessed as often. Making the refrigerator side accessable with a front loading door will reduce the amount of time the door will need to be opened to get things in and out. Now it requires removing several baskets to get what you want.

Are you sure about that? I'm thinking 25 Cu Ft s like... 6 shopping carts worth...

[Jammer]

Originally Posted by lifeofreilly57

The boat currently has a large inverter, but even the most efficient inverter is not that efficient.

Typical inverters are around 90-95% efficient.

I'm not as worried about the cost of converting to a 12V compressor but more interested in what kind of strain it puts on the battery bank and whats required to keep that battery bank charged.

A 25 cf fridge/freezer is large indeed, larger than most.

More typical ~10-15 cf sailboat coolers draw 3-5 amps with a duty cycle that varies approaching 100% in hot tropical weather, so up to 120 Ah per day. You would be around twice that.

Typical flooded 8D batteries are around 200-250 Ah. You have two. Refrigeration could end up consuming 50% of your bank capacity per day. I believe, given the large boat you have and the approach to cruising you are taking, that you would be well served to upgrade the battery bank. I would suggest using six 2V L16 batteries in series, which would give you just over twice the capacity you have today. You may also want to consider a 24V conversion as part of your refit, in which case you would want either eight 6V L16s in two banks, or 12 2V L16s in a single bank.

Anyone out there currently running a 12vdc refrigeration system on the hook?
If so how's it working for you?

I am not but as pointed out by many this has become the standard.

Originally Posted by lifeofreilly57

Currently it's built into the boat, it's about 25 cubic feet in volume, being bilt into the boats shape this is just a rough figure, I'll get an exact figure when I take more accurate measurements and run the numbers.
Right now it's one compartment and top loading. The insulation is about 3" thick, I haven't drilled into it yet to see what they used to insulation.
I am looking into sectioning off the interior of the compartment to make a freezer compartment.
It is currently a cold plate type refrigeration system. Running the compressor for one hour, twice daily usually keeps it about 38-40F inside during the summer months here when it's between 80-90F air temp. If I run it longer it drops below freezing.
If I decide to go ahead and divide up the compartment I'll add a front door to the regular refrigeration section but leave the freezer a top loading access door since it won't be accessed as often. Making the refrigerator side accessable with a front loading door will reduce the amount of time the door will need to be opened to get things in and out. Now it requires removing several baskets to get what you want.

Typically top loading arrangements require less power because there is less spillage of cold air when the door is open. I've had both on land, and there's no question that the front-opening doors lead to more frost buildup and use more power.

24 cubic feet is a lot. I used to raise cattle. If we had a steer butchered, I could fit all the meat in a 21 CF freezer and have room left over. That was enough beef to feed a family of four for a year.