Keel Cooled Refrigeration in Freshwater Tanks?

[TheNomadTrip]

Alright, I'm trying to think outside the box - bear with me.

I want to replace the fridge unit in my galley. It's an evaporator plate design - water cooled, but the compressor/thermostat/water pump are all in non-working order. I'd prefer to not replace the water-cooled system as it requires a separate pump to be on all the time - and it's something else to break/maintain.

So - I've been looking into the keel-cooled designs. But I really, really don't want to haul my boat again or put another through-hull in her.

Is there any reason I couldn't run the keel-cooler to my freshwater tanks?

Yes, I'm aware that it may increase the temperature of my freshwater slightly. That's no concern as I have a separate freezer aboard, where all my water is cooled before I drink it. In addition to having one less through hull, it seems like the (freshwater) keel-cooler should last longer with less cleaning than would be necessary if it sat in saltwater the whole time.

Thoughts?

-Nate

[crazyoldboatguy]

Interesting idea. I had considered water cooling using the on board tankage but that would still require the pump whereas the keel cooling unit doesn't. Perhaps you could just run the copper tubing thru the tank in a loop and dispense with the expensive keel cooling unit.

They do have those passive cooling units that attached to a sink drain thru hull - also passive in nature. However, I would worry about how to clean any fouling off this device.

I will watch this thread to see where it goes. Thanks for the suggestion.

[DeepFrz]

It seems to me that Richard Kollman is suggesting that air cooled, properly installed is the best type of refrigerator/freezer.

[TheNomadTrip]

Originally Posted by crazyoldboatguy

Interesting idea. I had considered water cooling using the on board tankage but that would still require the pump whereas the keel cooling unit doesn't. Perhaps you could just run the copper tubing thru the tank in a loop and dispense with the expensive keel cooling unit.

The unit I'm replacing was water-cooled and ran on my freshwater tanks. I talked to a couple of guys I consider knowledgeable and they strongly believe this increases the longevity of the components (pump/compressor).

The downside is that I needed to keep about 25 gallons in my freshwater tanks, which can be tough to do when your lady-friends like to take long showers...

[TheNomadTrip]

Originally Posted by DeepFrz

It seems to me that Richard Kollman is suggesting that air cooled, properly installed is the best type of refrigerator/freezer.

Even when the cooling unit is in a stuffy area, with limited airflow, and you're cruising in a tropical/sub-tropical climate?

I guess I should have relayed that info, sorry...

[Arthur Garfield]

As I wrote recently,Down in Mexico I've seen condensers replumbed into water tanks to very good results.

[TheNomadTrip]

Originally Posted by Arthur Garfield

As I wrote recently,Down in Mexico I've seen condensers replumbed into water tanks to very good results.

Any chance these were keel-cooled units?

Or were they water-cooled units?

[SV THIRD DAY]

Originally Posted by TheNomadTrip

Even when the cooling unit is in a stuffy area, with limited airflow, and you're cruising in a tropical/sub-tropical climate?

I guess I should have relayed that info, sorry...

Absolutely...unless you have some issue with not wanting the warm air going into you cabin, Laz, or boat Air Cooling is not only the KISS approach, it simply works without the drama of water cooling. Oh don't get me wrong, if you insist on water cooling for some reason, doing it in your water tanks is better than in sea water, but what happens when you lose a fitting and your water tansk drains...now you lose your refrigeration too?

[TheNomadTrip]

Originally Posted by SV THIRD DAY

Absolutely...unless you have some issue with not wanting the warm air going into you cabin, Laz, or boat Air Cooling is not only the KISS approach, it simply works without the drama of water cooling. Oh don't get me wrong, if you insist on water cooling for some reason, doing it in your water tanks is better than in sea water, but what happens when you lose a fitting and your water tansk drains...now you lose your refrigeration too?

Fair enough - but my current system is an evaporator plate, installed by Lagoon. I like the evaporator plate system (fruits/veggies), as I have a holding-plate freezer already (not as good for fruits/veggies).

So - if I have an evaporator-plate system, in a stuffy area, in my salon, when I'm going to be in tropical climates - would you still suggest an air-cooled system?

And other than what you mentioned (a failure in seal in my freshwater tanks) - why would one not use a keel-cooled system over an air-cooled system?

[SV THIRD DAY]

Originally Posted by TheNomadTrip

Fair enough - but my current system is an evaporator plate, installed by Lagoon. I like the evaporator plate system (fruits/veggies), as I have a holding-plate freezer already (not as good for fruits/veggies).

So - if I have an evaporator-plate system, in a stuffy area, in my salon, when I'm going to be in tropical climates - would you still suggest an air-cooled system?

And other than what you mentioned (a failure in seal in my freshwater tanks) - why would one not use a keel-cooled system over an air-cooled system?

Two questions:
1.
I would. If the location of your condensing unit is in a location that doesn't allow for a large enough "heat sink" of air volume, then I would install a air fan that trips on with the compressor with ducting to move the warm air out from around the unit.

2.
Do a search on this forum for Keel-coolers problems and if after reading through those horror stories still doesn't answer the question of why "air over water"....well.... Everyone knows that water is a better conductor of heat than air, so what most people then assume is that it is only logical and better to use water for cooling over air in these small marine systems. But the flaw in this "logic" ignores the maintenance issues of metal touching water, zincs, marine growth, etc.

The problem in trying to figure out what marine refrigeration system or approach is "best" is that what we typically get is ancedotal stories of "I love my unit", "I have this and love it", or "My system is the best". But rarely do we get the data that matters to help us evaluate: SqFt of Boxs, Temps in Box, Insulation type and thinkness, ambient temp, number of people aboard boat, daily Amp usage. "Mine is Great" doesn't mean much without data. A guy with 1380W of solar and a 400AH LiFePO4 battery bank may say his system is great but he doesn't care that his unit uses twice the power of what other systems would. Someone using their boat on a weekend, may love their unit, but what if they cruised full time in the tropics and were always trying to freeze all the lobster they were catching?

You also have to strip away the angle of people selling or promoting the units, which is why the opinions of Richard Kollman are so valuable here to listen to. He doesn't have an axe to grind or money to make by sharing his wealth of information and experience that Air Cooling is better than Water Cooling for the small BD35/50 type compressor units. He's just basing his opinion on years of being in the industry and more importantly years of repairing and trouble shooting systems.

[crazyoldboatguy]

Refrigerator systems remove heat from the cold side & put it somewhere. If the system is air cooled, then the heat is dissipated into whatever compartment the unit is in. If that is my cabin, aren't I putting more heat into the cabin? If I plan to go to the tropics, why do I want to put heat into my cabin?

The answer is I don't. I certainly don't want to use sea water to cool the unit - less holes in the hull is a good thing. Less pumps is a good thing. Using the drain cooler is interesting but you are still are involving seawater. I like the idea of using the water tank as a heat sink. I would put the entry and exit at the top of the tank, any leaks there would not involve the draining of the water tank into the bilge. Hell, I'd put a small tank near the unit and use that warm water for washing dishes.

I see this as a real positive. Interesting idea. If you already have the keel cooling unit, mount it in the tank and plumb it from the top. If not, I think a loop of tubing of some length would be sufficient to dissipate the heat.

[TheNomadTrip]

Originally Posted by crazyoldboatguy

Refrigerator systems remove heat from the cold side & put it somewhere. If the system is air cooled, then the heat is dissipated into whatever compartment the unit is in. If that is my cabin, aren't I putting more heat into the cabin? If I plan to go to the tropics, why do I want to put heat into my cabin?

The answer is I don't.

My thoughts exactly. And I also don't want my fridge unit struggling because I've installed an air cooled unit in an unfriendly environment. To me, it seems that in high temps, in a stuffy spot - you'd need some kind of cooling (other than air).

Originally Posted by crazyoldboatguy

If you already have the keel cooling unit, mount it in the tank and plumb it from the top. If not, I think a loop of tubing of some length would be sufficient to dissipate the heat.

I don't have the unit yet.

On the tubing - are you suggesting that a length of tubing would be OK without the keel-cooling? Or are you suggesting that I drop some tubing into the tank and just use that rather than a purchased keel-cooling unit.

I'm open to suggestions...

[TheNomadTrip]

Originally Posted by SV THIRD DAY

Two questions:
1.
I would. If the location of your condensing unit is in a location that doesn't allow for a large enough "heat sink" of air volume, then I would install a air fan that trips on with the compressor with ducting to move the warm air out from around the unit.

Understood. You don't feel that the high temps, etc would negatively affect the ability of the evaporator plate/reefer unit to cool? I specifically ask because on your site you list the following:

Evaporator Systems
Water Cooling Required at temperatures over 90 ° F (32 ° C)

Originally Posted by SV THIRD DAY

You also have to strip away the angle of people selling or promoting the units, which is why the opinions of Richard Kollman are so valuable here to listen to. He doesn't have an axe to grind or money to make by sharing his wealth of information and experience that Air Cooling is better than Water Cooling for the small BD35/50 type compressor units. He's just basing his opinion on years of being in the industry and more importantly years of repairing and trouble shooting systems.

I've tried to do some research here. Is the general consensus that if you're using a small BD 35/50 unit that you should stick with air-cooled units? it seems just as much trouble to me to duct a bunch of air from somewhere else, and install a fan - as it is to run a keel-cooled unit to my freshwater system.

Again, I'm just looking for the right answer (for me) and not trying to nitpick.

[DeepFrz]

I would suggest you go to Richard Kollman's web site and read the information he has there. Or look for Richard's posts here.

[crazyoldboatguy]

Take a look at the keel cooling unit and you get an idea of the surface area involved. Also, they have a unit that mounts in a sink drain that connects to a thru hull - a way to avoid yet another hole in the hull. The amount of surface area involved is not a huge amount. I haven't looked at it closely but can't think you would need much more than 18" of fully submerged tubing in a water tank. If you were bringing it in from the top of the tank you would need to keep the tank full at all times. That could be a pain. Bringing the tube in from the bottom doesn't require you to keep the tank full but it does add another way for leaks to drain the tank into the bilge - also not good. I haven't really thought too much about this yet - I am not at that stage right now. But it is intriguing. Really just a technical issue and quite doable. I know that many boats successfully have fan cooled units and they are quite efficient. I may well have 2 units as I am considering having 2 separate freezers cooled by 2 compressors. If I mount them in the same locale and try to fan cool them I am really causing some heat to be pumped into my hull.

I'd say ditch the keel cooler all together. Use a water tank to provide the heat sink. Even if you have to pump the coolant to and fro it still isn't a bad way to go. The pump failing has at least something to do with the fact that seawater is involved.

This is fun.