Keel Cooled Refrigeration in Freshwater Tanks?

[skipmac]

I just installed a new fridge in my boat. After hours of reading and research, including the purchase of Richard Kollman's books and reading every thread I found on this forum over 2-3 years I went with plain, vanilla air cooled unit.

I have been testing this in mid summer in north Florida. Outside temps every day in the nineties, boat interior in the mid eighties. Cannot imagine it is much hotter than that in Mexico.

I have a 9-10 cu ft box, about 2 cu ft of that is freezer, with a BD-50 compressor. Keeping the freezer temp around 12 F and box just above freezing, after initial cool down I'm using just over 40 amp hours a day.

Compressor unit is in a high spot in the bilge with reasonable air flow. Subjectively I feel no noticeable increase in the interior temperature, even in the area around the compressor.

Based on this performance I can see no reason at all to go with a water cooled, keel cooled or any other variation.

[crazyoldboatguy]

Sounds like your system works for you. I will be fitting my fridge equipment into a wood hulled sailboat. I would be leery of mounting any electrical equipment into a bilge. Just sayin….

[TheNomadTrip]

Originally Posted by skipmac

I just installed a new fridge in my boat. After hours of reading and research, including the purchase of Richard Kollman's books and reading every thread I found on this forum over 2-3 years I went with plain, vanilla air cooled unit.

I have been testing this in mid summer in north Florida. Outside temps every day in the nineties, boat interior in the mid eighties. Cannot imagine it is much hotter than that in Mexico.

I have a 9-10 cu ft box, about 2 cu ft of that is freezer, with a BD-50 compressor. Keeping the freezer temp around 12 F and box just above freezing, after initial cool down I'm using just over 40 amp hours a day.

Compressor unit is in a high spot in the bilge with reasonable air flow. Subjectively I feel no noticeable increase in the interior temperature, even in the area around the compressor.

Based on this performance I can see no reason at all to go with a water cooled, keel cooled or any other variation.

Glad you weighed in!

Do you have a fan running? Or is it just the reefer unit in the bilge?

I'm coming around...

[SV THIRD DAY]

Originally Posted by 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.

Great Advice.

Kollmann Marine

It's not a cop-out answer, but seriously, spend time on the Kollmann site and order and read his books. You will learn MORE than you ever really wanted to know, but then you will also have all of the knowladge to make your own decision rather than being pushed and pulled by folks with agendas (either to sell something or validate their own buying decision, which is 1/2 of what chat room advice giving is all about).

Going back to your earlier question about critical charge systems loosing efficiency above 90-degs F. Yes the condensor will lose some efficieny over the rated usage and specs at 70-degs. But even with this loss, stiking with air cooling is still a better choice than messing around with water cooling. To deal with this loss of condensor efficieny add some alternate air cooling to move as much air and heat out of the space as possible. There is a scale of efficiency and since you have ruled out a holding plate/expansion valve type unit for a critical charge/aluminum evaporator type, then you want to make the most of that system you can, which means stick with air cooled.


Now for the bonus nugget.
If your insulation is crap (and it is on the vast majority of production boats)...you can have the best most efficient unit known to mankind and you will still struggle to keep up with the Amp usage. The 40AH/Day reported above could EASILY turn into 80AH or more with **** insulation. Of course no one wants to believe that their insulation is crap, but after some testing to confirm it, we just helped a client replace the 2-3inches of soaking wet 1980 foam and now his unit is using 1/3 of the power it was using before the rebuild!

[skipmac]

Originally Posted by TheNomadTrip

Glad you weighed in!

Do you have a fan running? Or is it just the reefer unit in the bilge?

I'm coming around...

The unit does have a fan to cool the compressor/condenser unit. Mounted in a shroud to improve the flow over the appropriate areas.

While it is not loud it is audible, at least at night if you are sleeping in the main cabin but really not much louder than the refrigerant gurgling in the evaporator inside the box.

So if the very slight noise is a big factor for you then a keel cooler type system is quieter. For me, connecting the fridge components to the ocean with the risks of galvanic or stray current corrosion which could result in very expensive (as in replace the whole system) damage just isn't worth the minor benefits. Using the water tank will pretty much eliminate this concern but just adds some extra complexity. In my installation, once I had the box rebuilt the installation of the components was quick and easy.

The only glitch I had was a low voltage from using an existing wire to supply the compressor. The supply looked fine checking with a good meter, even under load but I was having startup problems. Installed new wiring one gauge larger and problem solved.

[skipmac]

Originally Posted by SV THIRD DAY

Now for the bonus nugget.
If your insulation is crap (and it is on the vast majority of production boats)...you can have the best most efficient unit known to mankind and you will still struggle to keep up with the Amp usage. The 40AH/Day reported above could EASILY turn into 80AH or more with **** insulation. Of course no one wants to believe that their insulation is crap, but after some testing to confirm it, we just helped a client replace the 2-3inches of soaking wet 1980 foam and now his unit is using 1/3 of the power it was using before the rebuild!

Yes, yes, yes. The only reason I'm getting such good performance is because I ripped apart the galley to remove the old box and put it all back together with 4-6" of insulation and a vapor barrier and reflective layer. Was a huge pain and by far the single biggest job in my refit but in the long run totally worth it.

[skipmac]

Originally Posted by crazyoldboatguy

Sounds like your system works for you. I will be fitting my fridge equipment into a wood hulled sailboat. I would be leery of mounting any electrical equipment into a bilge. Just sayin….

Maybe you need to fix all the leaks and dry out your bilge.

Seriously, I did think long before I installed the unit in the bilge. Soaking an expensive, new fridge system would by very annoying, to say the least. Never even thought about that option until I met another 422 owner who had done it.

In my boat I have a really deep sump aft of where the compressor is mounted and I also built a shelf for it that is about a foot over the bilge section so feel pretty safe with the location. If my compressor is getting wet I will probably have a much bigger problem to worry about at the time.

[crazyoldboatguy]

Skipmac, take a look at my avatar. Check out the pics on my profile page. My vessel hasn't been in the water for decades. Her bilge is dry as a bone!

Seriously, since the hull planking has been splined, I anticipate a dry bilge but one can't count on that in a wood boat. Everything has been done to make the hull as water tight as possible.

I am in a position, since I am essentially building a boat, to make major decisions before the accommodations are even laid out. That is why I am paying such close attention to what folks are saying here. I have read some of Kollman's stuff and am quite intrigued. I will be running 2 separate compressors that will handle to separate freezers which can also be run as fridges. 6" insulation all around both units which will be side by side. I would love to be able to just have air cooling - it would simplify things. I like the idea of installing the compressors in the bilge, tho. Those small things would not prevent me from seeing the condition of the structures that having tankage would. Removal for service/repair/placement would not be a problem.

Thank you for your comments.

[skipmac]

Originally Posted by crazyoldboatguy

Skipmac, take a look at my avatar. Check out the pics on my profile page. My vessel hasn't been in the water for decades. Her bilge is dry as a bone!

Seriously, since the hull planking has been splined, I anticipate a dry bilge but one can't count on that in a wood boat. Everything has been done to make the hull as water tight as possible.

I am in a position, since I am essentially building a boat, to make major decisions before the accommodations are even laid out. That is why I am paying such close attention to what folks are saying here. I have read some of Kollman's stuff and am quite intrigued. I will be running 2 separate compressors that will handle to separate freezers which can also be run as fridges. 6" insulation all around both units which will be side by side. I would love to be able to just have air cooling - it would simplify things. I like the idea of installing the compressors in the bilge, tho. Those small things would not prevent me from seeing the condition of the structures that having tankage would. Removal for service/repair/placement would not be a problem.

Thank you for your comments.

Oh I see. Guess you do have dry bilges, at least for now. Having been the owner of a wood boat in the past I can relate to the issues.

If you can find a high, dry spot in the bilges I really like that location for the compressor. Several reasons.

- takes advantage of a space that is otherwise not very usable but is still accessible for maintenance or repair.
- since it's down low it should be the coolest spot in the boat which will improve the efficiency.
- under the floors should muffle the little noise made by the fan.

By the way, check out my avatar. Not decades but that has been the home for my boat for the last 4 years.

[crazyoldboatguy]

I think it has possibilities. I can also get some separation between the compressors if I decide to have 2. I may also be mounting a pump arrangement in the bilge that will power a bow thruster. There is a company in Holland that makes one that acts more like a jet ski outflow than a tunnel design (which, as you know, would be a challenge in a wood boat). The purpose built unit is way more expensive than I would be willing to spend but I think I can do it w/off the shelf components and would likely end up in the bilge as well. As you said, the units would be more easily serviced and would be in a spot that is cooler and will have limited other uses, except storage. A person I know put his fuel/waste tanks in the bilge on a wood boat. I think it is a huge mistake since you can't keep an eye on structures that are prone to deterioration.

Thanks again, skipmac.

[TheNomadTrip]

Still doing a ton of research here.

Here's where I'm at:

- Keel cooled - virtually maintenance free when done correctly. Even moreso if mounted to my freshwater tanks (and I can do it without a thru hull or haulout). Quieter (no fan), more efficient, and generally better. Cruisers that I have alot of respect for choose this route (S/V Soggy Paws, for example).

- Air cooled - cheaper, simpler, but I'll need to install a fan and some ducting to move the air around. It'll also heat up my salon, which is a big deal in the tropics. Probably less maintenance, but I'll hear the fan, the fan requires power, and the fan could fail. This camp has some pretty strong support too.

It's really more personal preference at this point, me thinks. That said, I'm leaning toward KISS.

[crazyoldboatguy]

Those keel mounted units are NOT cheap. A BD50 with a fan unit and a bit of ducting is a lot cheaper. Kollman is very adamant that the heat generation in a ventilated space is not as much as one would think - he is clear on this. From a common sense viewpoint I have a hard time accepting that. But I haven't his experience.

An interesting discussion.

[skipmac]

Originally Posted by crazyoldboatguy

Those keel mounted units are NOT cheap. A BD50 with a fan unit and a bit of ducting is a lot cheaper. Kollman is very adamant that the heat generation in a ventilated space is not as much as one would think - he is clear on this. From a common sense viewpoint I have a hard time accepting that. But I haven't his experience.

An interesting discussion.

I've been running my fridge the last week to test the power draw and did not notice any difference at all to the temp inside the boat compared to the previous week. Even when I closed the boat up in the evening and come back 24 hours later when I open the hatch I certainly don't feel a blast of heat.

If I put my hand on the compressor, which is pretty small, it is warn to the touch so it doesn't seem like it would be generating that much heat.

Someone with more time on their hands could probably calculate the results.

[two fast]

Hi I have a Ozefridge Australian made freezer self installed 3 years ago it brings my freezer down to -26C and has both air and fresh water cooling
They offer great support and clear instructions.



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[TheNomadTrip]

Well crap. I thought I had it figured out, decided on an air-cooled unit.

But, the unit I'm replacing is a Frigoboat water-cooled system. And what I wanted to replace it with was a Vitrifrigo air-cooled unit.

I've learned that they're not simply interchangable. So I'd have to replace the evaporator plate as well. I'm not sure if this is the right choice anymore.

The issue is that I'm using the factory-installed (Lagoon), front-loading box and I would prefer to leave that intact... I've been told it might be better to replace the box as well - but that's an undertaking I'm not totally comfortable with as the unit doesn't look like it'll be easy to take out. And I'm not that confident in my ability to make it aesthetically appealing, if I needed to replace the whole thing. It's in my galley, so a half-assed job would be noticeable and bug me every day.

So, I could just replace it with another Frigoboat system. But that runs a little over $1K for just the compressor. The Vitrigrigo unit can be had for less than $500.

Any thoughts on this?