Generators

[Jentine]

"I would strongly advise not to go for an air cooled system. This is very inefficient by comparison with the keel cooled system. The water temperature is normally going to be a lot cooler than the air temperature!. "
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Your statement is less than accurate. A water cooled system may be more efficient if the temperature of the water is significantly cooler than the air in the bilge of the boat. In most waters this in not necessarily true. The charter companies in the Caribbean have chosen air cooled refrigeration due to its effeciency and simplicity. Fewer moving parts, fewer complications, fewer repair problems.
Three years ago I installed refrigeration and after checking with every major manufacturer of marine refrigeration, I installed an air system. No one with whom I spoke, had any specific data that extolled one system over the other so I chose the less expensive both in terms of purchase and installation. I have encountered no failure of the system to maintain the box temperature as it was set, nor has the system consumed excess energy to accomplish its task.

http://www.waecoadlerbarbour.com/ should satisfy your questions.

[CSY Man]

Tend to agree with Jentine:

Also installed an air cooled system over 3 years ago and have experienced no problems and high efficiency.

What more could one ask for....?.....

[Wahoo Sails]

Warm indeed! A dip in the water is much like jumping in a bath, this also makes anti-fouling a problem. Thank you Jentine for verifying what I had suspected (and CSY had suggested) for those of us in truly caliente climates .. the air cooled units are the way to go ... now ... the compressor & coils hang off the rear of the unit, they need air space to dissipate their heat, and so cannot be insulated, however, the box itself comes with minimal insulation .. so ... adding insulation around the top, bottom & sides would appear to be greatly beneficial ... c'mon all you rocket scientists out there ... what's the best way to do this?
By the way Wheels .. no fog when the air temp remains even higher. Many people think SW Florida is heaven on Earth, places rated guide puts Fort Myers in the 10 worst places to live climate wise ... add 85-100% humidity to the heat ..... sigh.

L S/V Eva Luna
Bob

[Alan Wheeler]

Pour in foam. You can also get it in a spray can. It's polyurathane foam and has excellent insulating properites. It's what is sprayed into the liners of fridges. It shouldn't melt the Polystyrene that is there now toooo much and it will stick to it like glue. The spray cans are great for area's you can't get into by any other means.

[ozskip]

Wheels you could still run both the freezer and fridge on one compresser condensing unit by fitting a pressure swicth to the unit and solenoid valves to the fridge and freezer.Insullation is your main issue but you are on the right track with close cell foam 60% more efficient than styren thickness is onething, quality of material is also important. You can get around the fact that their not along side each other although it is cheaper if they are together. Most of the work i do is large marine refrigeration on fishing boats any thing up 400 HP and most run multiple things off one unit. On the issue of air or water condensing both have advantages and disavantages air cooling easy to install,no holes in the hull,no electrolysis pretentual but downside only good for small units,tends to heat up areas with exhaust air,uses more power.Water cooling can be used on larger units,uses less power lower compressor head pressures,fewer moving parts if keel cooled,downside you must make a hole in hull,electrolysis pretentual unless you use titanium,keel cooling adds drag to boat,debris blocking heat exchanger ,corrosion,can be a nightmare to find a leak if in the condenser. Greg

[Talbot]

Greg,
Thank you for injecting some sanity.

Interested in how you actually run separate fridge and freezer from the same system, presumably the solenoid valves are operated by temperature from the fridge and freezer, is there some system of priority, or does it finish the job on one and then sense the other to see if it needs to continue, and where do you get the equipment to work such a system?

[CSY Man]

Well, I also run a fridge and a freezer on just one compressor, or just one "system"

The boxes are side by side:
I drilled a couple of holes in the wall between 'em and glued in a short PVC pipe in each hole. Also bolted on a small "door" so the bottom holes can be closed if needed.

This setup is called a "spill-over" system, where the cold air from the bottom of the freezer "falls" into the fridge, then when it warms up it rises and goes back into the freezer thru the top holes, to be cooled again.
If it gets too cold in the bottom of the fridge, I just close the little 2" doors and the process slows down.

Not usually necessary however as I keep feeding the fridge 1/2 a case of warm beer every 24 hours.
a few hours later the beer is nice and cold and the skipper is happily toasting the Sun Gods that so generously feeds the solar panels that feeds the battery bank, that feeds the compressor, that cools the beer.....

(Of course it does make a huge difference that my sailing is in the Florida Keys and the Bahamas with strong sun almost directly overhead.....In Alaskan waters in the winter, the solar panels would be pretty useless, but up there Nature cools the beer in a different way...Just put 'em on deck and no fridge is needed.. )

[Talbot]

For Jim Kane:

From Talbot: I would strongly advise not to go for an air cooled system. This is very inefficient by comparison with the keel cooled system. The water temperature is normally going to be a lot cooler than the air temperature!. "

Your statement is less than accurate

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FYI : Danfoss compressors are the heart of most modern decent fridge and freezer systems. The model 35 running small units, and the model 50 running the larger ones.

I quote from the Frigoboat Technical Data :

Danfoss BD 50 F compressor gives 36% greater output. Special thermostat valve achieves up to 50% more efficiency. Water-cooled using an outboard heat exchanger saves more than 20% compared to air-cooled in warm waters. No water pump, no water pipework. Extremely compact. The most efficient DC compressor available. Factory pre-charged with Frigoboat rapid couplings. Range of matching evaporators for refrigerators up to 400 litres and freezers up to 120 litres. Alternative versions with accumulator holding plates for fridges up to 140 litres. Automatic protection against accidental battery discharge. Optional automatic 230V power supply pack.

I dont claim always to be right cause I am not. But I do claim to thoroughly reseach a subject before posting data on it.

[ozskip]

The system has the fridge as priority as it does not run as long to get to temperture.Any good large refrigeration wholesaler have solenoids just buy the coil to suit your voltage.Something i forgot to mention about air condensers is they are rated for ambient tempertures standard is 35 c and go up to 50c these are the max air temperture where they will work at full efficency condensing hot gas. All refrigeration no matter what it is,is rated in KW or Btu at the condensers ambient temperture. Greg

[Jentine]

quote:I dont claim always to be right cause I am not. But I do claim to thoroughly reseach a subject before posting data on it.
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You, appartently, live sufficiently far enough north that the water is so cold as to not support any life forms in the water that will foul the external cooler and reduce it effectiveness in a short period of time. It is a reality that the manufacturer of Frigobot has chosen to ignore. Granted that each system has it frailties but the air cooled system for the type of boat that we generally discuss on this forum is more than sufficient.
My seven cubic foot refrigerator/freezer with air cooling maintains the internal temperature of the box to the prescribed setting while the compressor runs 50 percent of the time. My neighbor, with a similarly sized system that is water cooled has the same operating cycle. What is the difference? His cost more to purchase and install. For the difference in price, I could install two air cooled systems; one for refrigeration and another for the freezer, or I could simply use the additional funds to fill the fridge with some good British ale.

[Wahoo Sails]

Hey CSY Man,
Have a 125 watt panel on the way (along with the charge controller) ... only thing left to do was to find a suitable fridge. Lo & behold ... picked up a 2 cubic foot Norcold (works as new) for $100 !!!

L S/V Eva Luna

Bob

[CSY Man]

Ooh Wahoo.

Is the Norcold one of them compact, stand alone units that ya plug in with a cigarette lighter socket?

If so, they ain;t all that efficient, they run 24 hours a day.

I own one, currently for sale for $400.00

(It was given to me for free, I had it serviced and tested it at home for a week before I put it on the market.)

Again, based on my humble experience, the best thing I have ever done was to add insulation to my ice boxes, then install an air-cooled Cool Blue unit with an oversize holding plate and lots of ventilation and fans blowing over the compressor unit.

It runs 3 hours per day (24 hours) in the Florida winter at the lowest setting, and 8 hours per day in the Bahamas in July with everyday use. (Lots of warm beer added)

The amp/ per hour has been from 4 to 6...I guess the compressor runs at different speeds..it senses the voltage available and runs harder when the batteries are fully charged, but takes more amps per hour in doing so.

The final result however is les than 50 amp hours per day in the summer for BOTH fridge and freezer...Hard to beat I'd say.

IF I only ran a fridge on the same system, I am guessing that the max daily amp/hour penalty would be 15 and perhaps down to 10 in the winter.......

[Wahoo Sails]

Happy to say it's not the unit you described. has both AC / DC inputs and is auto sensing. hooked it up while it was 80 degrees here and on it's #3 setting, it cooled from ambient and cycled off in about 10 minutes. Unfortunately, there are no specs on it ... but I have to think this will be way more effecient than the absorbion unit I'm using currently.

L S/V Eva Luna
Bob

[PM]

Have you thought about a Northern Lights. They run at 1800 RPM and have a good reputation. I have a 6Kw on my boat. Uses just over a quart of fuel an hour under moderate load. Heavy load about a half gallon. Smooth and relatively quiet.

[irwinsailor]

PM, I would have no problem buying a Northern Lights but I can get a new Phazor 6.5 floor model at dealer cost. I have not bought anything yet but the Phazor looks to be what I will be buying when I sell somemore stuff.