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Old 09-11-2010, 17:40   #1
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Engine-Driven Refrigerator


So I'm considering buying a boat with an engine driven Sea Frost refridgerator (not my first choice).

My question is this, can you plumb a 12v DC system in line with the engine driven system. Something with valves in the line, so if the 12v system quits, you can switch back to the engine compressor? That would mean using the same cold plates in the refer box as is already installed.

Will I have to totally remove the engine compressor (and 120v AC backup) system if I want a 12 v DC system instead?

BTW, this is on a Mason 44.



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Old 09-11-2010, 21:49   #2
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The short answer is yes. BUT, you didn't say how big is your box, what is the insulation material and thickness. your box might be too big for one 12V compressor.

Can you give more info?


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Old 10-11-2010, 03:36   #3
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I don't have the cubic footage, but it's a good sized refer and a big freezer on a Mason 44. I don't know what kind of insulation is in there, but it seems to be sufficient.

I was guessing I'd need two compressors, one for the refer and a separate one for the freezer.

Where could I get reference material to take on a project like this. Any good books you can recommend or web sites detailing this kind of work?

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Old 10-11-2010, 04:28   #4
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I'm not sure if that will work. The engine-driven compressor cools the eutectic solution in the holding plates way down below zero celsius while normal compressors use different temperature/solution/pressure for cooling; so I think that you would need 2 distinct systems. That is a good thing, since you can use the ample energy from the engine-driven system to cool down things then the 12V DC system to keep it cold and have a fallback.
My last boat had an engine driven compressor and it really worked well, cooling down the plates and contents in about one hour and I would only need to run it every second day. But when at anchor or in a marina I either had to waste main engine runtime or resort to purchasing ice ashore and using that for cooling.
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Old 10-11-2010, 04:58   #5
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Richard Kollmann KollmannMarine Boat Refrigeration Specialist maintains a web site with a technical forum where this sort of question is routinely answered. (Don't miss the slide show on his web site.) He also sells two DIY books on marine refrigeration. With his help I have rebuilt the engine drive refrigeration system on my boat which has as a backup a 110v system. The two are entirely separate except they share a holding plate in which they each have individual evaporator coils. His own boat had both engine drive and 12v refrigeration.

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Old 10-11-2010, 05:16   #6
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What Zanshin said (post #4).
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 10-11-2010, 05:25   #7
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There may already be a second circuit in the holding plate, there was with the system on my boat. It turned out that it was almost cheaper to replace the whole system and simplify the system.

Seafrost is a very good company to deal with, the owner Cleave Horton, is the main point of contact and is willing to discuss existing systems, alternatives and make recommendations. Their customer support is excellent.
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Old 10-11-2010, 12:42   #8
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With solenoids in the liquid and suction lines you might be able to
keep the engine drive system. I've never heard of a system like that.
Backup/dual systems usually use separate circuits in the holding plates.

Get Kollmann's book and check out I built a 12VDC system
with rparts compressor/motor and stuff from Grainger 11 years ago and its
still going strong. I used Grunert, now Marine Air, plates.

The reefer and freezer have a common suction line with solenoids in the
liquid lines. Separate thermostats and a simple relay control circuit drive
the solenoids.

A DC system does use a lot of power so a big battery bank and solar/wind
charging is a must to reduce engine run time. We use about 100AH daily
during the summer depending on ice making, beer/food loading, etc. Winter
usage is less but I don't have a number for that.

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Old 10-11-2010, 14:19   #9
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Thanks for all the great responses. Looks like I should get Kollman's book and go from there.

Nice installation John, you do nice work.

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Old 10-11-2010, 14:55   #10
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When I made the decision to cruise in the tropics and live aboard I faced the refrigeration question.

I decided on an engine drive with a cold plate that could make ICE ie a freezer. I warm freezer is a refrigerator.

Part of my calculus was that I definitely would be using the diesel almost every day... and this would make electricity, hot water and could run the compressor. With 12v refer I would also need lots of battery stored energy which meant... running the engine or more charging sources.

I installed a Grunnert Caribbean engine drive and it works a charm. What I typically do when living aboard is have a "noisy hour" once a day in the AM after breakfast. This is to run the engine, cool the refer, recharge the batts (high output alternator, do the dishes, take a shower and vacuum. At the end of the noisy hour I have topped up batts, a full supply of hot water for the day and a cold refer... and I don't have to sit there listening to the engine because I am busy doing chores!

Of course when I motor to the fuel dock, in and out of anchorages and so forth I replenish all the above - cooling, electricity and hot water.

I don't have to have extra batts, though mine are quite large - 2 8Ds for house. Since I don't stay at docks I need to make my own energy and by diesel is my main power generator.

The longer I run the refer the colder it gets. For passages I get it down to freezer temps and use an extra cooler for things which require refer temps... and move them onto the top of the refer where it's warmer as the days progress and we consume the frozen stuff.

Since I have to run the engine to make up electrical needs using it for the refer has been a good solution. But I hate the noise of the diesel.

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