Refrigeration via Frigoboat
This is really a followup to an earlier thread on this site when I was just getting started on the idea of installing refrigeration on our boat. What works for others might be quite different. My installation could be an example to copy, or perhaps serve as a warning to others...
Not knowing the cubic footage of the box on the Mk 2- 35, I have no idea of the evaporator size you might want. Our ice box on the '88 Olson 34 was about 3 cu. feet. I got this by measuring the inside for gross dimensions, as though it were a retangular box. Then I measured the part that was not part of the real "box" that was in the missing section where it was stepped back from the curve of the hull, and subtracted from the first amount. Another way to have done it would have been to view it as a larger box shape sitting on a smaller (lower) box shape, and just add the two together.
Either way I got the cubic measurement in inches and converted to cubic feet.
I discussed my plans with the technician at Boat Electric in Seattle, since I was buying the parts from them. Our particular box has about 3 inches of rigid foam all around the sides and bottom, from the Ericson factory. The top is mostly lid, and was not insulated. I added an inch of closed cell foam rigid insulation with the aluminized surface (from the local building supply store) to the lid and the underside of the remaining top. It is held inplace with double-sided tape.
The hardest part of the job for a newbie like me was just "imageering" the crowded installation for the little compressor and routing the stiff copper lines.
I used the "keel cooler" from Frigoboat (
http://www.frigoboat.com/home.html) to miximize efficiency and for lowest power usage. We installed the "keel cooler" (i.e. a flat plate of sintered bronze with a small coil of copper inside) during a haulout for a bottom job last March.
Here is a page with some photos of one being installed on a C&C, from Wally's awesome web site:
http://www.wbryant.com/StellaBoat/hauls/0307/haul.htm. Scroll down quite a ways on the page to see the installation of the keel cooler.
I designed an aluminum bracket to support the compressor under the lower shelf under the galley sinks. Most of the pre-charged copper lines were coiled up in that area and secured with plastic ties when the job was done. Like another member of this list, I had to drill a two inch hole in the upper corner of the ice box and feed the copper lines through as the evaporator was eased into the box through the lid opening. I did not kink the lines, but worried about this a lot (Too much, actually....). I plugged that air leak around the tubing with foam bits and sealant, and put a piece of matching formica(r) on the inside to cover the hole and fit tight around the tubing.
Advice I got from the dealer was to go with the larger of the two possibilities of evaporator sizes that their chart reccommended -- larger is always better. The plate had to be bent 90 degrees, in a portion of it that is intended for bending without pinching the coolant channels. We built a bending jig on the lip of my work bench with the needed min. radius. I had a piece of 3.5 inch OD pipe handy to make the bending radius from. I also tried a sample bend on some old scrap copper tubing to be sure that both sides of the resulting right-angle bend would come out to the proper length.
FWIW, after about my third phone call to the shop (
http://www.boatelectric.com/) in Seattle, the guy chuckled and told me that my only problem was that I think too much!
I bought the following parts:
Evaporator Plate 130F SM $136.
Compressor, Keel, K50 SSC 600.10
Keel Cooler w/zinc 374.
Thermostat (refrigeration) 28.90
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Total was about $1139.
This was Feb. of 2004, and they gave me the winter boat show discount.
Obviously, it would be a little cheaper to go with the heat exchanger radiator and fan right on the compressor. I wanted the least amp usage, no heat generated inside the boat on a hot day, and least noise. [One more disclaimer: my solution is not the best or only answer, of course.]
As to amps, it proved to be quite thriftly during our two week vacation this summer. Our house bank (picture elsewhere on this site) is two Trojan T-145's, which is 235 amphours. We anchored out for two days and I checked the voltage with a digital meter -- I lost .2 of a volt per day from a fully-charged bank. What with having a spare starting battery, we figure that we could have gone about three days without running the engine. We have a stock 50 amp Motorola alternator on a Universal 23 hp diesel.
It was so quiet that you had to try to listen just to hear the faint purr of the compressor.
The Admiral is happy, and so, therefore, is the Captain. Not having to plan a vacation around the search for increasingly-rare block ice was just wonderful.
Lastly, we put a cork in the old drain outlet to keep valuable cold air from flowing down into the former drain hose.
If I have left out any steps, drop me an email.
Best,
Loren in PDX
Olson 34 #8