keel cooling air conditioning

[jerry f]

Can anyone explain how keel cooling works and is it an appropriate option for new air conditioning installs on sailing craft?? Does it still require a through hull and water pump??

[GordMay]

A Keel Cooler is basically an Air-Conditioning/Refrigeration Condenser (the Hot part) which is mounted outside the underwater hull, often on the keel (hence the name).

There are least two (2) hull penetrations required (refrigerant supply & return). There is no water pump">raw water pump.

The Compressor generates a high pressure gas, which is circulated through the condenser (keel cooler), where it is cooled (by heat exchange with the sea-water) and condesed, then fed to the Evapourator where it cools the Frige/Space, and finally returns to the compressor.

The system does not use raw water, nor pumps - so is viewed as “simpler”. The Keel Cooler is, however, mounted in the sea-water, where it is at risk of mechanical damage & fouling, and creates extra drag.

Keel Coolers are not common on sailboats, and I cannot recall a successful sailboat installation. My experience /w keel coolers is very limited.

A few references about KEEL COOLERS:

MSC Guidelines for Review ofCooling System/Keel Cooling System
http://www.uscg.mil/hq/msc/PRGuidance/e1-05.pdf

From CFR Title 46:

PART 119—MACHINERY INSTALLATION
http://www.washingtonwatchdog.org/do...6/part119.html

PART 128—MARINE ENGINEERING: EQUIPMENT AND SYSTEMS
http://www.washingtonwatchdog.org/do...6/part128.html

and

Marine Keel Coolers for Heat Dissipation
http://www.flagshipmarine.com/keelcool.html

FRIGOBOAT - Frequently Asked Questions
http://www.frigoboat.com/faq.html

HTH,
Gord May

[Talbot]

Your report on keel coolers is correct as far as those versions that use a length of pipe outside the hull are concerned. But, there is another version of the keel cooler which takes the refridgerant into a bronze block which acts as a heat sink to the external waters, thus there is only one hull penetration, and no more likelihood of problems than the standard SSB grounding plate (which it closely ressembles.

[GordMay]

As usual, Talbot is right (single hull penetration).
I didn’t mean to imply that penetration(s) were a disadvantage of Keel Coolers, just that I saw no advantage either.
Gord

[Strygaldwir]

I use the keel cooler distributed by Frigoboat in their refrigeration systems. As Talbot shows in his picture, it consists of a bronze fitting with the refrigerant lines running through it.

It has the advantage over a traditional cooler in that it only requires one hole in the bottom of the boat and there is no electrical pump motor, strainer, wires and hoses that present their own installation and maintenance issues.

I questioned the Frigoboat folks on the applicability of using this type of cooler for air conditioning. They said they do not support its use in air conditioning. This may have been due to their compressor not having enough capacity for effective cooling.

I love the set up so far. I have two. On for a freezer and one for the refrigerator. It was easy to install. It has been effective in these systems and there have been no problems. It is expensive though!!!$$$

[Talbot]

What compressors are you using and how large are the fridge/freezer. What sort of current draw? I have liked the look of the frigoboat set-up and keel cooler, but have been looking for some real figures from people in hot climes.

[Strygaldwir]

First, I am using the 50F compressors with smart speed controllers (SSC). What this does is adjust the speed of the compressor to compensate for loads. It generally has 5 speed ranges that it will go through in an attempt to optimize power consumption. When power is applied to the box it starts off at the middle speed seting, then move up, or down depending on the thermal load in the box. Works great!

We are currently in North Carolina, for several weeks the tempertures have been in the 90's. Abysmally hot!! The water temperature got up ot 92 at one point! I found it hard to believe, had to double check it. Yep, 92. For the most part after turning off the major devices, I saw 1-2 amps being drawn through amp meters. 90% of that had to be the refrigeration. I still have meters, 3 Co monitors, propane sensors, and bilge sensors still pulling amperage. I suppose I could turn the refrig off and get a baseline use. I'll probably do that when I get back down to the boat next week. But in any case, I'd say my consumption runs in the 1.5 amp per hour range. We also have Corel digital thermometers on both the refrig and freezer. The box temperature goes up about 3 degrees when we open the box. It takes about 3 minutes or so to go back down to 38. Occassionally we see the box temperature creep up to 41, but it usually back down to 38 within an hour or so. The documentation suggest that this is correct behavior. Anyway, it works REALLY well! I am very happy with it. Even though it was a significant investment, and I did spend some time rebuilding and insulating the boxes. We have a 9 cu foot frig and 8 cu foot freezer. They are some what on the edge of what the literature suggest. But, I think the insulation and having seperate boxes have contributed to making the system a pleasure to use.



Keith