Keeping the fridge/freezer cold while sailing

May 2, 2019
136
Hunter 38 Annapolis, MD
I'm in the process of purchasing a 2006 Hunter 41 DS. It has a Separate front loading Refrigerator and Freezer.

I was told that when not at a slip with electric that the fridge/freezer would not run?

I know on most rvs that when the electric is turned off that the propane kicks in. Is this not the case?

It has a Northern Lights 6KW Generator, does this need to be running to keep the fridge cold? A little confused but sure someone can set me straight.
 
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May 2, 2019
136
Hunter 38 Annapolis, MD
If this is correct do you need to turn the engine on from time to time to keep up the charge on the house batteries? Is there is certain period of time that the house batteries can die down without the engine engaging and charging? Reasonable times that is. I'm sure if you left it going for days you will have dead house batteries. Thank you too for the post!
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
You should have gotten owners manuals when you bought the boat. There are at least several ways to set up your system. If 12 volts, you have to run the gen to charge the batts to run the fridge. Just like the barebaots I've chartered.
 
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Jun 11, 2011
1,243
Hunter 41 Lewes
Firstly you need to know the amp hour size of your house bank of batteries. Every one’s house bank seems to change overtime. Mine is currently 630AH. I consider my boat a dock queen and so she is usually plugged in every night. I have been on four day sails and have had to run my 5.5KW gen for about 5 hours on the third day. There is a lot more going on than just the fridge and freezer.
 
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Dec 4, 2018
60
Balboa 27 Denver
1. There are no propane fridges on boats, they are dangerous.
2. To answer this question, you will need to know a bunch of details, including, specific fridge design and power draw (12 volt of 110), size and age of battery bank, size of engine alternator and onboard charger. Report back with these details and maybe we can help. From the context of your post, you will learn ALOT in the process. Welcome to the forum.
 
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Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
Sum up all of the amperage ratings of each device you will be using on a given day. For me it is not much, just a depth sounder and an auto-tiller. If I'm sleeping out, I will also run a fan. Lets say you come up with 5 amps total with all of your devices running at once. If you have a 100 amp-hr battery bank, then you can run all of your stuff for 20 hours before you need to recharge your battery (100AH/5A=20H). I picked those numbers just to make the math easy so you will need to input your own numbers.

Of course running your battery down that hard is not good on your batteries so using this scenario you would cut that number in half and run for ~10 hours before you should recharge. Add a solar panel to the mix and you might be able to double that number.
 
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May 2, 2019
136
Hunter 38 Annapolis, MD
You should have gotten owners manuals when you bought the boat. There are at least several ways to set up your system. If 12 volts, you have to run the gen to charge the batts to run the fridge. Just like the barebaots I've chartered.

I haven't purchased the boat as of yet. I'm certain there are manuals but not in my possesion. I'm pre prepping myself while waiting on the bank.

Thank you all for commenting that helped very much and now I know what to expect.

More or less the generator will have to kick on from time to time to maintain battery life. Or the engine I assume.
 
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Jun 15, 2012
694
BAVARIA C57 Greenport, NY
On my 2007 41DS I can run the refrigerator & freezer for around 6 hours on the batteries alone. My boat only has 2, 4D AGM batteries (there is space for three). As far as I know most marine refrigerators and freezers use a Danfoss now Secop BD-35 compressor and 101N0212 controller, which I am 99% sure the boat you are interested in has installed. The controller will automatically reduce the operation of the compressor as the voltage fed to it drops. The admiral will often remark how he freezer works better when we are connected to shore power. When the boat voltage drops to 12 volts or so I turn on the generator. An excellent upgrade would be to install a Balmar battery monitor which is much better than just looking at a voltage meter.
 
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May 24, 2004
7,129
CC 30 South Florida
Boats are no longer equipped with propane refrigerators, they are either 12V or 120V. If your will not run without shore power it is likely a 120V unit and you will have to run the generator to be able to operate the refrigerator. A front loader unit will allow cold air to spill every time you open the door. It is best to carry a separate ice cooler for drinks and snacks so as not to have to open the fridge too often. Find out the model of your refrigerator and google it online and it will tell what is the power source voltage and operation capabilities. Refrigerators are very reliable and they seem to last longer when used 24/7.
 
May 24, 2004
7,129
CC 30 South Florida
1. There are no propane fridges on boats, they are dangerous.
Years ago they were it. I remember having one hooked up by copper tubing to a portable tank sitting on top of the cabin. At the time our noses were the sniffers and the shut off valve was at the tank. It also operated the stove. We were very aware of what was going on when the valve to the tank was open and to this day I shut off the valve to the tanks when the stove is not in use.
 
Dec 4, 2018
60
Balboa 27 Denver
Boats are no longer equipped with propane refrigerators, they are either 12V or 120V. If your will not run without shore power it is likely a 120V unit and you will have to run the generator to be able to operate the refrigerator. A front loader unit will allow cold air to spill every time you open the door. It is best to carry a separate ice cooler for drinks and snacks so as not to have to open the fridge too often. Find out the model of your refrigerator and google it online and it will tell what is the power source voltage and operation capabilities. Refrigerators are very reliable and they seem to last longer when used 24/7.
The cold air spilling out and reducing efficiency is a myth. Air has almost no latent heat, and it is what you have in the fridge that maintains the cold.. that is why it is good to have a full fridge, as the compressor cycles less often. Front and chest type are about the same. It’s a hard myth to die, and people have been struggling with deep hard to access chest fridges and freezers for many years for no reason.
 
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Dec 4, 2018
60
Balboa 27 Denver
Years ago they were it. I remember having one hooked up by copper tubing to a portable tank sitting on top of the cabin. At the time our noses were the sniffers and the shut off valve was at the tank. It also operated the stove. We were very aware of what was going on when the valve to the tank was open and to this day I shut off the valve to the tanks when the stove is not in use.
Gosh, I guess I should have said, nowadays there are no propane fridges on boat but many many years ago there were although, I been cruising for better than 50 years and never seen one.
 
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Oct 26, 2010
1,883
Hunter 40.5 Beaufort, SC
Assuming it is a 12V refrig/freezer operated from the house bank when not on shore power/generator/engine then leaving it on when you are not powered by one of your chargers is probably a loosing game. It may be a "risk" to leave it on if you are away from the boat and the boat is connected to shore power. Unless you have a very big house bank or a sizable solar power source you are likely to ruin your very expensive batteries just to keep something cold. Even if you have one of the 120V sources that operates a charger or a solar panel, it is probably a good idea to have a "low voltage shutoff" device that disconnects the loads if the battery drops to a certain level. I believe I remember Mainsail making this recommendation. Even if you're hooked up to shore power someone can come up and unplug you (I had it happen to me) or the marina breaker can trip, etc. If you don't have something to protect your battery from a deep discharge it will be a very costly mistake. If you are only going away for a few hours, then fine but to leave a 12V reefer (Navy for refrigerator) on for an extended period of time without something to protect the batteries is probably ill advised. How much beer can you buy for the cost of a couple of expensive batteries?
 
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
More or less the generator will have to kick on from time to time to maintain battery life.
Our boat has a similar arrangement as the one you might take ownership. A front/top loader fridge and separate top loader freezer, both operate on AB 12VDC power. Over the years we have made several extended two month cruises in PNW waters and most always anchor out rather than spend time in a marina. Our house bank consists of two 8D AGM batteries that hold just under 500 AH.

I keep both reefers on 24/7. The house bank supplies enough power to operate the reefers and the rest of our power needs for at least two to three days depending upon ambient temperature. Every other day I run our 8kw Genset for about 1.5 hours, to heat water for washing/cleaning, some cooking and topping off the house and starter banks. That has worked for us over the years.

What we have and do works for these cruising grounds. Yours likely a bit different due to the heat and humid summer Florida conditions. We have dual reverse cycle heat pumps (suspect your boat does, too), but never use them during the summer; never gets that warm here. Normally, I will use them while connected to shore power in our slip when we stay on the boat during the winter months. A diesel forced air furnace that I installed several years ago keeps the boat warm while out cruising off season, which we often do.

Hope this helps. Please let us know when you take possession and whether we can help with other questions you might have. I know this site was immensely helpful back in the day when we were considering upgrading from our H28 to the boat we now have since 2002.
 
Oct 26, 2010
1,883
Hunter 40.5 Beaufort, SC
In regards to my comment about leaving the boat with the refrig/freezer running I was assuming the OP was considering leaving the refrig/freezer running when leaving the boat for a long time unattended. When they are cruising overnight or for weeks on an end for that matter, they can monitor battery status and start the generator or running the engine when it gets below their "threshold" for charging as has been pointed out by others. My bad - I misunderstood their question. I think its still a good idea to have a "low voltage relay" to cut power to non-essential loads if battery power gets too low. "That's my story and I'm sticking to it."

Isotherm makes a controller that can be used on existing Danfoss compressors (I think so anyway) that lowers the setpoint for cooling the refrigerator to a lower temperature when it senses you have external power like on shore power or a generator. This "subcools" the items in the refrigerator and allows you to take advantage of that cooler temperature of the items in the refrigerator to take advantage of contents to help hold the temperature. I am pretty sure Jackdaw has one of these and I have one and am very pleased. It helps with the energy budget a little and every little bit helps.
 
Jan 12, 2016
268
Hunter 410 Ladysmith, BC
1) Determine the size of the house bank in amp hours.
2) Try and figure out by watching how many amps your fridge draws an hour.

We added a Victron Battery Monitor that essentially counts the amps drawn out whenever the battery isn't getting charged, and expresses it in a %. At 60% you should be topping the charge up on your bank, never getting down to 50% unless you want to shorten the life of the bank. Without solar, most boats can go two days on their house bank if it is appropriately sized and the fridge is efficient.

We add those camping blue freezer packs to the bottom of our freezer to half the volume and reduce current draw. Our freezer is larger than we need to use when only out for two weeks. A filled fridge/freezer with all items fully chilled while on shore power will be far more efficient on your batteries than a half empty one, or one that is used to chill items at room temperature to fully cold.
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
Most 12V coolers have a transformer that allows you to plug into a 120V AC source on the boat. So when on shore power, make sure you are using a 120V plug and not the 12V plug. That way you are not taxing your batteries when at the slip.