Hi Dave, I only saw this thread earlier today. As another Little Harbor owner (46' 1988) and having done this sort of conversion I hope I can help. I have to admit first that I have not read every word of this long thread so I apologize if I repeat anything already said (even tho I never want to be "that guy..."). I'm not a BTU measurement kind of guy, but I am an engineer
with a good sense of what works. I obsessively researched what to do, finding there is no perfect answer as this thread points out. There is ultimately the best choice with the least compromises. I have no experience with engine
I'm not on my boat (but will be Friday) which is currently in Grenada
. I did the refrigeration refit
myself 5 years ago so I know my boxes well. I'd guess my fridge is ~11 cf (vertical door), and the freezer
~7 cf (top loader.) Insulation is probably like yours at 3", but I'm guessing. My sense is that it could be somewhat better, but I believe overall I started with quite good boxes. I had a Grunert system with big holding plates in both boxes and two compressors. One ran on 120vac and one on 12vdc. A big manifold managed the flows. Two separate water pumps circulated raw water
. The old gear
took up three full lockers below the seats of the settee. The boat shook and rattled any time one of the compressors kicked in. You could just feel the energy be consumed/wasted.
I went to the Newport Boat Show
and looked at every possible system and spoke with reps in depth
, and talked to the experts at my yard. In the end I chose a Frigoboat keel cooler
system here: https://www.coastalclimatecontrol.co...frigoboat.html
. I have the K50F compressor and 200F evap plate in my fridge . Same compressor and one plate size smaller in my freezer (don't know model #, the seller helped me work
out the largest size I could fit in my freezer, and I think it was a special order). I have the digital controls and compressor management add-ons. All good.
Why this choice:
- Very low energy usage. Having no water pump
and no fan is an obvious elimination of power draw. Of course modern compressors change everything compared to my old beasts.
- I couldn't imagine having a fan blowing across the coils and putting that heat into the boat, especially in hot climates. That just seems crazy to me, but maybe I'm over thinking that and it's not noticeable.
- Simplicity of installation
. It's all pre-set and charged. Literally plug-and-play. No help needed to evacuate and fill the refrigerant. That said the installation
is not for the faint-of-heart handyman. There's a lot to it.
- My boxes got noticeably roomier by removing the freeze plates and putting in evap panels
- the promise of it being nearly dead silent - and it is.
Does it work
- It's been flawless operationally. It just runs.
- I've seen comments here about run-time per day for various solutions but I have to say that they are so quiet, and so out-of-mind, and so enormously better then the old stuff that I've never really measured it. Clearly the freezer runs a lot more than the fridge, but I can't give an honest answer to the power consumption
other than to say it is not an obvious killer burden on my system.
- I've had no trouble in the warmer waters from Bermuda
. I'm sure they run more frequently just like any fridge would with a higher temp differential between inside and outside the box. I have no sense that the keel
coolers are less happy in warmer water. They just work...
What would I change:
- In practical usage both my boxes are bigger than they need to be. Even with six crew aboard for an ocean race
or transit my wife can provision 10-12 days of frozen meals
and fresh stuff in the fridge. But that's the extreme case, not our normal 2 - 4 person island hopping/coastal cruising. For normal cruising we have more cold room than we need, so using more energy than we need to. If I had known this when I did the refit
job I may have added insulation and shrunk the boxes.
- With the above lesson learned I may have designed the fridge to have a small freezer section - enough to make/hold some ice for sundowners - and only run the big freezer box on long passages or in places where regular provisioning
is more sketchy. That's not really in our cruising plan. We won't be doing a circumnavigation
Just for fun here's a picture of one of my old compressors with a new one sitting in front of it. If I didn't tell you the new one was there you probably wouldn't see it:
Multiply this disparity by two. When I'm back on the boat I'll send a picture of the new setup. I have both compressors in a small locker under the stove
that I never really used for anything, so it feels like they take up no space and are invisible. I absolutely loved getting back all the space the old system took up, and the boat probably lost
I hope this helps. Good luck with your system.