[C38] Refrigeration

Wed Dec 30 13:24:38 EST 2009

Hi Steve,

I don't remember the amperage of my compressor.  Also, when I wrote, I forgot to tell how I ran a 120v AC compressor on 12v DC.  I have a 1000 watt Heart inverter with a remote switch which is mounted on the bulkhead behind the refrigerator.  I also have a transfer switch mounted under the sink which transfers several 120v outlets to the inverter.  The inverter itself is mounted under the pantry in an area which was previously a void area.

Because my modern inverter is over 90% efficient, my total refrigeration ampere load is similar to a pure DC machine which usually are less efficient than a 120v. AC compressor motor. The higher efficiency of 120 volts offsets the loss of the inverter.  

When I'm using the inverter, I have outlets that transfer loads to the inverter.  One outlet is mounted in the sail locker which runs the refrigerator and also allows me the use of electric drills etc in the cockpit.

Another switchable outlet is mounted  below the end of the aft cushion of the dinette and forward of the access door under the sink.

Another switchable outlet is under the navigation table where my microwave is located.  One final switchable outlet is mounted at the aft end of the electrical panel over the quarter berth.  With an extension cord, I can have 120v power anywhere on my boat while underway.  Once I even tested an 8,000 BTU air conditioner with my 1000 watt inverter just to see if it would work.  I expect that would suck the battery down pretty quickly but it did work for a test.

Even if someone uses a new, out of the box, marine conversion refrigeration system I still recommend using a copper tube loop around the perimeter of the bilge for a condenser.  This allows you to discard the fan and motor if you have an air cooled condenser and if you have a sea water cooled system, it allows the elimination of the seawater pump and thru-hull.

I have measured the return temperature of the refrigerant line near where it goes to the evaporator and in every time I checked it, the return line was cooler than the ambient air temperature which is totally impossible with an air cooled evaporator.  When I measured the refrigerant temperature as compared to the sea temperature, there was always less than 4 degrees difference.  That's pretty efficient considering the only moving part in my system is the refrigerant compressor. 

The sea water systems have about the same return temperatures but they have the added electrical load of the energy hog water pump which my system doesn't have or need.  I am not too excited about extra thru-hulls and water strainers either.

Tom Troncalli

----- Original Message ----- 
From: Steve Smolinske 
To: tdtron at earthlink.net;Catalina 38 Listserve
Sent: 12/30/2009 11:17:07 AM 
Subject: RE: [C38] Refrigeration

Tom how did you make the conversion from AC to DC, do you have any idea on what your amp draw is?

From: listserve-bounces at catalina38.org [mailto:listserve-bounces at catalina38.org] On Behalf Of Tom T.
Sent: Wednesday, December 30, 2009 4:25 AM
To: Catalina 38 Listserve
Subject: Re: [C38] Refrigeration

Hi Steve,

My refrigerator conversion is crude but extremely efficient.

I bought a new refrigerator at Sam's Club and gutted it putting the evaporator on the ourboard side of my ice box and I put the compressor in a small enclosure in my sail locker.  I ran the high side refrigerant line around the perimeter of my bilge and it works wonderful!

You could make the salt water cooling line work like my condenser line if you purchase a commercial unit but with my unit there is pump or associated noise.  The only moving part is the compressor that is mounted in a fiberglass enclosure in the sail locker which is hard to hear, even from inside the sail locker.

Because of the extreme efficiency of my unit, the batteries last a long time, even in the hot Florida environment.

I had actually already made my ice box conversion some years earlier from a small dormitory refrigerator I had bought at a flea market but the compressor failed. I tried to buy a new compressor but they wanted something like $145.00 for a new compressor but it would have to be ordered, not in stock. Sam's membership warehouse had a two door, large dormitory type refrigerator new in the box for $110.  My boat is 500 miles from my house so it was a no brainer, the new complete refrigerator it was.

The people on the dock thought I was insane when I opened the box and took out the refrigerator, took out the compressor and evaporator and threw the rest of the brand new refrigerator into the dumpster. 

I once talked to the people at the Largo Florida Catalina plant about using the keel for a refrigeration and engine cooling heat exchanger but they were not too interested.  I thought if they stubbed in connections to cast in place cooling tubes in the keel it would make cooling of the engine and refrigerator very efficient but it seems that the sailing manufacturing community is very conservative about new ideas.

I've owned and worked on many marine refrigerator systems and my boat using the 1" of water that is always in the bilge for a 1/4" copper tube condenser is extremely inexpensive, efficient, quiet and space saving.  Using the bilge for a condenser is a no brainer.  I can even use my refrigerator when the boat is on the hard if there is any residual water at all in the bilge.  Try that with a sea water cooling system.

Tom Troncalli

----- Original Message ----- 
From: Steve Smolinske 
To: Catalina 38 Listserve
Sent: 12/30/2009 12:18:01 AM 
Subject: [C38] Refrigeration

I have searched through the last few years of posts and didnt see any discussion on refrigeration systems so I have a few questions for those of you with them.  I am considering the Isotherm 4201 or the Virtrifrigo both use the danfoss BD35F compressor for a max of 8.8 cubic feet ( Our boxes are 5.6),  Both have ASU holding plate options and both use seawater for cooling the compressor.  I am thinking of teeing off the engine raw water intake and draining through a tee in the galley sink drain.   The nice thing about the virtifrigo is that it has a holding plate that will fit nicely on the aft wall of the upper ice box on the port side.  It is 11 X 2.5 x 8.  Any other size will interfere with the main ice box area.. 

Questions are :  

1)  anyone have any recommendations or warnings on brands?
2) I'm sure there is some math for figuring out the proper size of holding plate for cubic volume, anyone?
3) As an option what about making the cooling line a closed loop and running the tube from the compressor pump through the bilge and back to the compressor, that would be preferable to teeing off at through hulls If the run is long enough to cool the water before heading back to the pump.  

Thanks

Steve
Peregrine #312
Seattle
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