Confused about marine Fridge's,

Don S/V ILLusion · Feb 27, 2008

better get some bigger batteries

at a cost which may exceed the price difference in refrigerators which typically draw around 5 amps at 12VDC. That would equate to a 110VAC compressor draw on an inverter of 60 watts...By comparison, a small "dorm room" refrigerator we have on the porch draws 800watts which at 12VDC would be around 70amps through an inverter.

Landsend · Feb 28, 2008

Good answer from Don...

If you think boat parts are expensive, wait till you buy something for an airplane.

Richard Bryer · Feb 28, 2008

There was a thread

in the archives about using a small bar fridge (120v). I believe the owner put the cooling unit into the existing cooler in his boat. I took a quick look and couldnt find it. I also saw a picture of a 34 not too long ago with a larger- looked to be 4 ft high or maybe a bit more - set up in the place of the existing cooler. It was even stainless steel. Now that would not help the built in H34 starboard list!!.

Daryl · Feb 28, 2008

Diference = Price

The last Norcold I worked on had a compressor that operated on 20 volts AC. There were transformer / inverter electronics built in the unit to make 20VAC from 12 VDC or 110 VAC. The fridge cooling is basically the same. I've taken many dorm fridges apart and installed the guts in boat ice boxes with great success. Putting these parts in a well insulated box I find they don't run very long or often. Hooked to a pair of golf cart batteries through an inverted you can always have cold beer for under a hundred bucks

Ed Schenck · Feb 28, 2008

Dorm fridge works well.

The previous owner of my boat removed the stove/oven and inserted a dorm fridge. I think something must be wrong with Don's porch fridge because mine is rated one amp at 110v AC. It runs less than half time and uses about nine amps of 12v DC. So I round up and figure about 5 amps per hour. I also have a 12v Adler/Barbour in the icebox that is not much better than that.I leave the dorm fridge and the AC on all of the time. The beer and pop is always cold when I get to the boat.

Steve Dion · Feb 28, 2008

Dorm frig at the dock only.

If you only want to keep your beer cold and the mayo from spoiling while you are not around then the dorm unit can do it for you.I have seen the guts pulled out of the refrigerator and installed in the icebox which makes a nice installation if that is what you are really looking for.On the other hand if you want to spend several days out sailing and anchoring you don't really have much of a choice. You will need to look at a 12vdc unit.Some of these units are very low battery consumption (less than 1 amp/hr). This is dependent on how much insulation you can get into your box.We ended up getting a Isotherm SP unit. It uses NO FAN but the compressor pump the coolant thru a fitting (sink drain) in the hull (like a keel cooler). These units have a couple of advantages. The first one is that they are totally water cooled. The coolant is cooled to the temp of the surrounding water. The unit does not pump heat into the cabin area and there is no fan to listen to. I have not actually measured the actual power consumption but the factory reps are quoting somewhere between .8 - 1.5 amps.

Benny17441 · Feb 28, 2008

To make the comparison fair you have to

consider the cost of the inverter and its installation. For a dorm refrigerator that consumes around 1 amp at 120V you will need at least a 1200 Watt inverter with soft start. A non-marine inverter will run you $150-$200. An inverter that size will need to hard wired with heavy gauge wiring, a #2 or #3 depending on the roundtrip distance between the unit and the batteries. A 150 to 200 AMP fuse will be needed to protect against fire. Between the heavy gauge wiring and the fuse expect to spend another $100. So now you will have an $80 refrigerator with a $250 inverter for a base total of $330-$380. It will still run you less a marine unit and the inverter may be used for a TV or another 120V appliances. Anticipate that the power consumption will be approximately 3 amps per hour. The compresor will only cycle for about fifteen minutes of each hour. This will vary with the starting temperature of the fridge or the ambient temperature of the air. Some of the new units don't have a fan and are quite silent. By contrast a marine unit will consume around 1 amp per hour. The marine environment is harsh and although these dorm fridges are very reliable the inverter may not last as long unless you get a marine inverter but now you are talking $450-$500 plus plus wiring and fuse. There is no doubt that if the boat already has an inverter the addition of a dorm refrigerator is the most sensible way of doing it.

Gary16395 · Feb 29, 2008

This is sounding even better

Benny,1amp at 120V is 120watts... That's a pretty small inverter requirement!Its going to draw 10+amps(+startup) from the 12V but that's not a problem, you just need enough battery capacity aboard to keep it going as long as you want.But, its already set up to run back at the dock.Daryl,So the marine frigs actually run on AC and have an inverter already?I have a small refrig that I want to get around to stripping and installingin my icebox on my H320, this project is sounding better all the time!GaryH320 Time BanditEmeryville, CA

Benny17441 · Feb 29, 2008

Gary, read the posting and check your formulas.

If you can run a dorm refrigerator on a 120 0r 200 Watt inverter you can probably walk on water.

Gary16395 · Mar 1, 2008

NO but..

HI Benny,I wouldn't try that but I do have a 1500watt(3000watt surge) that should workfine. It cost $85 as I recall (Costco Xantex, not marine but..).I just checked, my "dorm" fridge (Sears, actually taller than the smallest dormtype) only takes 0.9A at 120V. That's running and there is a big surge at startup I know (does anyone know how much that would be?).Gary