Frigoboat Keel Cooling Refrigeration in Temperate Cold water?

[s/v Jedi]

Originally Posted by Cheechako

I had a cold machine with the optional sea water cooling. It also had the standard fan. When the water pump">raw water pump started acting up I just abandoned it and activated the air cooling circuit. I really could tell no difference in the amount of daily charge time either way. (how do you really ascertain 5 mins extra running without getting real anal about it?) I like the simplicity of the pumpless keel cooled devices, but if you are looking for big electrical gains in a small boat unit, I suspect you wont find them. Maybe different in a big unit.

With keel coolers you don't have that raw water pump that draws 2 amps or so. That almost halves the total draw when running, makes a big difference.

[Richard Kollmann]

jr_spyder, On most boat water cooled condensers there is a way to control the process of condensing gas vapor to liquid and still maintain adequate high pressure by not over condensing needed to maintain an efficient refrigeration process. On larger pleasure boat systems that pump water through condenser a flow restriction or a water bypass diverter is use to control high pressure.
Even larger systems use hot gas bypass valves or high pressure regulator to control water flow through condensers. The problem with these very small water cooled Danfoss BD compressors systems is there are no inexpensive ways to control condensing high pressure. Danfoss engineering spec sheets do identify condenser gas temperature for highest btu output. Looking at most efficient condensing gas temperature for BD50 compressors Danfoss lists 55 degree C (131 F). In this case the colder the cooling medium the lower the high pressure on refrigerant flow control device. I like to see refrigerant line temperature coming out of condenser between 100 and 115 degrees F this then insures liquid pressure at expansion device of over 105 psi and under 125 psi.

The only thing that I am looking for is at what low water temp is this small keel cooler unit not functioning at all. Most system work less in cold water climates so the loss of btu capacity will go un noticed as long there is still some cooling in the box.

[Frigoboat Info]

To all interested parties. Please be advised that Frigoboat Keel Coolers are designed, engineered, and have been thoroughly tested by tens of thousands of boaters, to work in freezing water, tropical, and everything in between. Of course there are performance differences with varying condensing temperatures, but the loads are substantially different also. The limiting factor at the high temperature end of the scale is not so much the design of the Keel Cooler, but rather the condensing point of the refrigerant. When the delta temperature between the refrigerant and cooling medium is insufficient, not all of the refrigerant gets condensed and some flash-gas will be mixed in with the liquid refrigerant causing loss of efficiency. That's why water cooled systems are so much more efficient than air cooled systems in warmer waters, where the air cooled system's performance is compromised by both the elevated air temperature and the limited volume of air that can be practically passed over the condenser. You'll typically see some initial flash-gas formation with R134a at around 95 F condensing medium temperature.
Frigoboat Keel Coolers will also work quite well out of the water, in open air, with no temporary cooling water rigged up. But doing so will void the warranty and will carry a high risk of O-Ring failure (very common), head gasket burning (i.e. toasted compressor), and all sorts of other nasty things associated with operating a machine in conditions that it was not designed for. If rigging up temporary water cooling for a Keel Cooler proves to be too much of a hassle, we have a pre-charged "Air Add-On" air condenser available that can be installed very simply on all BD35/50 Frigoboat Keel Cooled or Pumped-Water Cooled systems. The fan is switched off while the boat is in the water, but then switched on if the boat is hauled for emergency repairs or if a navigational snafu dictates a few hours high-and-dry while waiting for the next tide.

[Cheechako]

Great to hear from you! thanks

I once tried to use my on board water cooled air conditioner while the boat was on the hard by having two 5 gal buckets of water which would circulate into the AC unit and back into the buckets. Haha, the unit overheated and shut down in less than 5 minutes use! So some significant heat exchange is necessary.

[Dockhead]

Originally Posted by Frigoboat Info

To all interested parties. Please be advised that Frigoboat Keel Coolers are designed, engineered, and have been thoroughly tested by tens of thousands of boaters, to work in freezing water, tropical, and everything in between. Of course there are performance differences with varying condensing temperatures, but the loads are substantially different also. The limiting factor at the high temperature end of the scale is not so much the design of the Keel Cooler, but rather the condensing point of the refrigerant. When the delta temperature between the refrigerant and cooling medium is insufficient, not all of the refrigerant gets condensed and some flash-gas will be mixed in with the liquid refrigerant causing loss of efficiency. That's why water cooled systems are so much more efficient than air cooled systems in warmer waters, where the air cooled system's performance is compromised by both the elevated air temperature and the limited volume of air that can be practically passed over the condenser. You'll typically see some initial flash-gas formation with R134a at around 95 F condensing medium temperature.
Frigoboat Keel Coolers will also work quite well out of the water, in open air, with no temporary cooling water rigged up. But doing so will void the warranty and will carry a high risk of O-Ring failure (very common), head gasket burning (i.e. toasted compressor), and all sorts of other nasty things associated with operating a machine in conditions that it was not designed for. If rigging up temporary water cooling for a Keel Cooler proves to be too much of a hassle, we have a pre-charged "Air Add-On" air condenser available that can be installed very simply on all BD35/50 Frigoboat Keel Cooled or Pumped-Water Cooled systems. The fan is switched off while the boat is in the water, but then switched on if the boat is hauled for emergency repairs or if a navigational snafu dictates a few hours high-and-dry while waiting for the next tide.

That's a lot of trouble just to have refrigeration when hauled or aground. I would just shut it down, I think.

The Isotherm system is allowed to be used on air alone, according to the manual, and I have used mine all winter on the hard without any problems (in fact I didn't notice any reduction of efficiency, even). I guess it works better on air because the coils have a good bit of surface area exposed to a convective air flow through the deck drain (and actual water when it rains).

The Frigoboat system has been original fitment on Oyster Yachts for decades and has an excellent reputation. Everyone I know who has one is very pleased with it. I guess you shouldn't run it dry, however.

As Nick said, keel cooled refrigeration is the way to go -- no extra run of sea water in the boat (risk of leaks; extra through-hulls and sea cocks), less complexity, significant savings in power.

[sestina]

2 Atlantic circuits on 2 different boats, both with the Frigoboat keel cooled system. Worked very well, even keeping my beer frosty cold in the Florida ICW in June. Fridge only, no freezer.

The ECOnomy controller is a worthwhile addition. It works best with holdover plates. It senses the system voltage and box air temperature. When the voltage is high, ie: motoring, it works the compressor hard, pulling the temperature down. When the voltage is reduced the air temperature sensor takes over and allows the box temperature to rise to 10C and runs the compressor slowly. Saves a lot of amps, and can be overridden with the push of a button.

[s/v Jedi]

We use one of those micro sprinklers to keep the keel cooler temp down. They are sold to be used with potted plants etc.

[Tortuga's Lie]

I retrofitted my icebox with a Frigoboat keel cooler a few years ago and I am very happy with it. It's been extremely quiet, just a small hum from the compressor. In fact, you really have to strain to hear it when's it's on. I also later added the digital thermostat/controller and this seems to make it a bit more efficient. I don't know exactly but I estimate that mine consumes around 50 amp-hours/day. I'm in the Chesapeake where the water temps range from 42 F in the winter to 84 F in the summer.

[Frigoboat Info]

Good advice from Jedi, who I see has a Sundeer 64, the brain-child of brilliant designer and engineer Steve Dashew. Steve has 3 x Frigoboat Keel Cooler systems on his 84' power boat "Windhorse", and that boat has been well travelled and the systems thoroughly tested in all temperatures and conditions. The same set-up is standard equipment on Steve's FPB line of long-range powerboats that morphed from Windhorse.
Sestina mentions the ECOnomy device and holding plates from Frigoboat, both of which are from another era. Although that was a good combination it had limitations. Now, thanks to the super-efficiency of aluminum evaporators mated with Smart Speed Controls, Keel Coolers, and Danfoss (now Secop) compressors, we provide systems that are even more efficient while providing greater flexibility, and the ability to handle fridges up to 20 cu ft and freezers up to 10 cu ft.
Thanks to Tortuga's Lie for the input. The most common report on performance we receive seems to be about 20-25 amp/hrs per day for a 6 cu ft box, in the Caribbean, with Keel Cooler and average insulation. We could crunch the numbers for days on end and come up with all sorts of data for all sorts of conditions and scenarios, but real-life reports are what really count.

[Richard Kollmann]

Frigoboat info, I for one would like to see how Frigoboat can crunch their own figures to refrigerate a 20 cubic foot box to 33 to 48 degree F refrigerator using Secop/Danfoss BD80 LBP DC compressor in tropical warm seawater? If you could request they quantify there figures as they relate to Danfoss application engineering specifications for the compressor you are referring to.

[Frigoboat Info]

Mr. Kollmann. I'm sure you don't need me to help you run these numbers? You will no doubt have the Danfoss specifications for the BD50 handy, so you can easily determine what capacity the BD50 is rated for at refrigerator evaporator temperatures and at 130F condensing temperature. Then if you consider the heat load of a 20 cu ft refrigerator box in tropical use, even with minimal insulation, you will see that the BD 50 compressor has way more capacity than needed to maintain temperatures, even at the slowest speed and at 130F condensing temperature, (far higher than we see with a water-cooled system in the tropics). It is because we have so much excess capacity that we can usually slow the compressor down and make it even more efficient (higher COP). It is also why we have no need for the extra capacity of the BD80 compressor that you refer to, which is slightly less efficient than the BD50 and uses a different, less reliable controller.

[Strygaldwir]

I have two Frigoboat systems aboard, one for the freezer, the other for the refrigerator. I use evaporators for both systems. My boat is currently in the Annapolis area on the Chesapeake. I have not explicitly monitored my power consumption during the winter months; I can say anecdotally that power consumption from November to April, when I have kept the boat in the water was half or more of that in the summer months. Power consumption I must say has been the strong point of the system. It has been exceptionally good. Any issues I have had I attribute to not being able to follow Richard Kollmann’s advice on insulating the freezer. I was able to insulate the refrigerator, and it makes a HUGE difference.

In Caribbean water, I saw 5 -6 amp/hr. draws on the freezer for about 16- 20 hours a day. This was something on the order of 100 amp/hr per day. On the refrigerator it was more like 35 amp/hours a day.

[Strygaldwir]

My water temps have been bellow 42. One winter I had to chip about 4 inches of Ice from around the boat. I imagine the temp at the depth of my coolers to be around 36 or so.

[Frigoboat Info]

Strygaldwir (Welsh?). Am I correct in thinking that your systems were factory installed in France by the boat builder? If so, then it is not surprising that insulating the fridge box made a big difference, as there are many aspects of installations by European boat builders that typically fall well short of perfect when those vessels reach this side of "The Pond". You don't say what components you have installed, or what volume your boxes are and what temps you keep them at, but if you will please send us some pictures of your installations we'll be happy to make some recommendations that could make your systems even more efficient. A picture paints a thousand words ......

[Richard Kollmann]

It is truly good to see someone officially or not from Frigoboat or any other company defending his products on the web especially with our present economy. Many of Frigoboats products perform well in a market where many companies are disappearing although their model brands remain under a major marketing group without much aftermarket support. . Glacier Bay and I understand another refrigeration company are not in the boat refrigeration business any more.

Frigoboat Info: You stated, “Mr. Kollmann. I'm sure you don't need me to help you run these numbers? You will no doubt have the Danfoss specifications for the BD50 handy, so you can easily determine what capacity the BD50 is rated for at refrigerator evaporator temperatures and at 130F condensing temperature. Then if you consider the heat load of a 20 cu ft refrigerator box in tropical use, even with minimal insulation, you will see that the BD 50 compressor has way more capacity than needed to maintain temperatures, even at the slowest speed and at 130F condensing temperature, (far higher than we see with a water-cooled system in the tropics). It is because we have so much excess capacity that we can usually slow the compressor down and make it even more efficient (higher COP).”



You must know this statement disagrees with documentation offered by companies selling systems with Danfoss BD 50 compressors. I admit my conservative recommendations based on my knowledge are arbitrary when I fail to support creative advertising. If you have watched My slide show {What Works And What Does Not} on my web site, a 20 cu ft box is not a candidate for capacity of a BD50 compressor application. You said you could crunch the numbers I would like to see them. Performance is defined by the following:

• Ambient conditions
• Box size
• Insulation R value
• Desired Controlled temperature in box
• Daily amp-hrs consumed
• BD50 compressor Speed.

When I look at an installation application for a cruising boat’s refrigerator I use a basic guide:

• Determine worst case planed cruising climate for this refrigerator’s application
• Smart engineering with new variable speed BD compressors is to design for their running time to be less than 50% duty cycle. Optimum energy efficiency is achieved when desired box temperature can be maintained at the slowest compressor speed and still less than. a 50% duty cycle.
• Box size and planed use will define size of refrigeration system. Boxes smaller than eight cu ft can be efficiently cooled to refrigerator temperatures in warm climates with Danfoss BD compressor/condensing units. Refrigeration capacity larger than eight cu ft boxes in tropical climates will require compressors much larger than a single Danfoss BD50.
• Freezers in tropical climates with Danfoss BD50 compressors are limited to 4 cu ft