12 volt or 12/110 volt fridge

[eastont]

What is the difference between a 12volt dc only fridge or a 12dc/110ac fridge, beside the price ?

The 12 volt only would be running off battery, but at shore the battery would be getting charged, so I can't see why to go for both.

All comments are appreciated.

 

[MH Hawker]

Its a matter of amp draw, at 12 volt the draw is a lot more than at 120 volts so when your at the dock its easier if its switched over to 120 VAC.
You can however ever run it on 12 volt at the dock but it will keep the battery's in a state of charging and shorten their life span and then their is the gassing to deal with.

 

[alldodge]

Agee with MH and will add, if your staying out over night you could get by with a 120V only.

I have a 12/120 in my cruiser but never let it go to 12VDC. Use to do that, and every once in a while the marina would get a surge or something which would trip the main breaker. Come down to the boat and find the battery dead and stuff spoiled. Now if it does it I only have warm stuff and not a battery to deal with

 

[gm280]

I have no idea what the cost difference is between the two options, but personally I'd go for the 12/120 volt setup and have everything covers either way. And who knows, one day you may want to remove it and put it in your shop or even sell it and the dual function is a great option to offer. Would be nice to have it work in any place. But that is just my opinion...

 

[doyall]

Determining which would best suit your needs is dependent on how long you would require it to operate on batteries alone compared to your battery capacity. For long times away from shore you may want to consider a generator if you have the proper space. If I had shore power available and especially if I planned on leaving it on 24/7 there is no way I would not get a 12/120 unit and use 120 at shore. Also, your battery charger is probably not designed to be used as a constant power source and if it is not, it will burn out relatively quick. On a related note, I would also go for a compressor/condenser unit as opposed to a Peltier thermoelectric unit.

 

[shrew]

Agee with MH and will add, if your staying out over night you could get by with a 120V only.

I have a 12/120 in my cruiser but never let it go to 12VDC. Use to do that, and every once in a while the marina would get a surge or something which would trip the main breaker. Come down to the boat and find the battery dead and stuff spoiled. Now if it does it I only have warm stuff and not a battery to deal with

What model fridge do you have? Do you have an external AC/DC switch on the fridge. All dual-volt Norcold fridges I've ever seen the switch is internal and automatic. Either the fridge is on, or its off. If it's on and sensing 120VAC, it switches to AC automatically. If there is no AC, it switches to 12VDC automatically. I can turn the AC breaker in the panel off, however this simply forces the fridge to switch to 12VDC.

The only I would be able to do this would be to turn the 120VAC breaker ON, and the 12VDC battery switch OFF. Then if I lost AC power the fridge would get no power at all.

 

[shrew]

As to the OP's original question. With a 12v only fridge, you would be pulling from battery and replenishing from battery charger when on shore power. This reduces the number of AMPS being charged in the battery and would lead to longer time to recharge the battery. If you're primarily in the marina this is not a big deal. I sit for days on the anchor and use a generator to recharge my house bank. I prefer to have the fridge running AC off of the generator to reduce the load on the battery while I'm trying to recharge it.

 

[H20Rat]

What model fridge do you have? Do you have an external AC/DC switch on the fridge. All dual-volt Norcold fridges I've ever seen the switch is internal and automatic. Either the fridge is on, or its off. If it's on and sensing 120VAC, it switches to AC automatically.

I have a relatively new norcold in my RV that is dual voltage that allows selection. (technically it is also propane, so maybe its an RV feature...) Anyway, the default mode is auto with 120v having priority, but if you hold down the mode button, it will put it into manual mode, and you can tap mode again to cycle through the inputs.

 

[eastont]

I bought the 12 volt only version. It is a Nova Kool RFU9000.

I have been told by a marine type person, who is well versed in fridges, that the dual voltage model is both inefficient and hard on the compressor.

The Nova Kool is made for 12 volts and on the dual voltage version, they put in a small transformer to reduce the voltage from 120-12.

We spend most of our time either on the hook or tied up to an island without any power, so it will always be on 12volt.

I plan on installing solar panels on the roof of the aft deck to help with the 12 volt power.


But I will need a solar expert to guide me on the type and size on the panels.

 

[gm280]

How many amps does that 12 volt unit draw? Because I bet you will have to cover the entire boat with solar cells to even help much at all with the huge number of amps it draws. Compressors, any type compressor is a power hogs for certain... It is just the way they are because of the job they have to perform. Compressing refrigerant takes a lot of force, hence a lot of current/voltage...

 

[IslandPhil]

I don't have a fridge on my boat but here is what I am looking at for a fridge on shore at my off-grid solar cabin/cottage.
It should work for your boat:

1) a 110volt Danby or similar 4.4 cubic foot bar fridge.
- no freezer, all fridge so no defrost heating.
-about $200
- only 1.1 amps @110volts = ~120watts
2) when on the water, use an Inverter to provide the 110v. It would draw about 11 Amps at 12v only when running.
- most shut off before the batteries are drained/ damaged
- cheap and readily available

 

[bruceb58]

Like GM380 said, you are going to need your whole boat covered in solar panels for this to work as well as a huge bank of batteries.

As far as the transformer being hard on the compressor, you do realize that when you are at the dock, you are going to need something to supply 12V off the 110V right. Guess what? It's going to be a transformer/power supply/charger of some kind.

 

[eastont]

Now that I have a 12 volt refrigerator, I am going to place solar panels on the hard top above the aft deck.

But here's the problem.........I know even less about this, actually I know absolutely nothing.

I've surfed the net and I'm so confused I'd fail having to answer what my name is.

I know there are many on here who are quite educated in the solar panel department so all input is appreciated.

BUT !!!!!!!!!!!!!!!!!!! Please remember who you're dealing with here so make all your comments/suggestions as simple as possible for my very simple mind.

I read what the commander said and I'm not so sure about that. Last year we met a boat that had two 4' X 6' attached to the bow rail and he said it supplied power for his fridge, a 12 volt cooler and everything else on the boat. And he said he had not been to shore in almost two weeks..............................
Thanks

 

[bruceb58]

Do you have enough room to mount 48 square feet of solar panels on your roof like this guy did?

Solar panels that are laid flat can generate around 750Watts/square meter. That should easily work for what you need. You are going to need a failr large bank. Probably 210A hour capacity so you only need to draw down 50%. You never want to draw down more then 50%.

 

[eastont]

Do you have enough room to mount 48 square feet of solar panels on your roof like this guy did?

Solar panels that are laid flat can generate around 750Watts/square meter. That should easily work for what you need. You are going to need a failr large bank. Probably 210A hour capacity so you only need to draw down 50%. You never want to draw down more then 50%.

I have about 144 square feet, so am I okay for this ?

 

[bruceb58]

I would say yes.

Not going to be cheap though!

 

[bruceb58]

You have two steps to consider here. How much current you are drawing per day is going to determine both the size of your panels and the size of your battery bank

Let's say for example that you average 5A per draw hour. That means in 24 hours you will consume 24 x 5= 120A. Each 100W panel will produce 6A/hour or 30A per day if in 5 hours of sun in the summer. You will need at least 4 100W panels.

As far as the battery size goes, you really need to max discharge your battery 50-60%. If you are drawing 120A then your battery capacity needs to be between 240AH to 200AH. 2 Trojan 6V T105s 6V in series will give you 225AH.

For the whole system including batteries, solar panels, controller and cabling, you may be spending $1500(Just a WAG).

If you plan on using any more draw for other 12V needs, you need to bump up the values I just gave as an example.

 

[gm280]

Ha, I'm with you if you can afford the solar panels AND maintain the batteries and such. But don't buy just enough solar panels because I can tell you the advertised output is taken with everything going perfectly. Use you head and understand that you have to go way above what they say about the panels or you will not be a happy camper...I mean boater... You have to figure in over cast days, rainy days, partly cloudy days. The nice pretty sunny days are the good days for solar panels, but even then solar panels that basically lay flat will not put out current as if there were directed exactly towards the sun. You will be using them with the sun at angles most of the time. The only time they will work to their advertised output (or there about if at all) will be when the sun is directly over the flat panels... It can be done, but expect to buy more panels then simply adding up their possible capabilities and thinking you have everything covered... And do read the fine print on them. I'd bet they actually specify their usual output somewhere on the packaging. And the average output will be way different then their big printed outputs. I really good scenario to compare such is with how cars are posted with their gas mileages on the window stickers. And then you buy it and can't get half their projected gas mileage without turning the engine off and coasting down hill all the time. And that is because they have perfect setting to produce their specs. JMHO!

 

[bruceb58]

Yep, you want to derate the panels at least 25% for laying flat. Panels are rated at 100W with an output voltage of 16.5V or so. That is how I came up with the 6A.

Best thing to do is talk to a panel company that supplies RV users. They know the best.

Buy a controller that can handle 40A and then you can always add panels if the number you buy is not enough.

This is not a bad site to educate yourself.
http://www.amsolar.com/

 

[eastont]

I would say yes.

Not going to be cheap though!

What on a boat is cheap.....................LOL