Reefer System Design

[PeteW]

Tore out the old rotted AB evaporator and got to looking at what is left of my refrigeration system. Doing the math I quickly came to the conclusion that whats in there was never big enough for that huge refrigerator box in the 365.  (air cooled  danfoss DB-35 1/20 hp compressor)

That would include any system with a Danfoss DB-35 or DB-50 compressor so the aircooled Cu-100 and CU-200 from AB are not going to anything other than cool. Believe these to be similar HP Dometics units.  I concluded that to get any portion of the box divided up for freezer operation it is going to require a Danfoss DB-80 compressor and a hold over plate. That system appears to be an Isotherm ASU 4901 water colled system. Its got the DB-80 compressor. It appears you can't get there with air cooling either so its got to be water cooled. AB does not make anything that powerful.

Since I have never seen this system work I have no baseline for performance. I'm interested in leaning what solutions have worked out there and how well.

Thanks,

Pete W,  Pearson 365 Ketch #6

[RayNWanda]

I built and installed a 2M kit from Rparts. I used a "C" holding plate and upgraded to the Carel digital thermostat. I built a 2" foam partition covered with formica and used about 1/3 of the box for a freezer, the rest for a fridge, It works great. It is based on the Danfoss BD-80 and is water cooled. I think Rparts says the "C" holding plate will work on a 11 cubic foot refrigerator or a 4 cubic foot freezer, don't remember the specs, but it has plenty of horsepower for a 365 box. We kept ice cream in it for a week July 2010. The fridge side stayed at 36 degrees. There are some pics here:

http://www.littleyachtsales.com/searchlittleyachtsales.php?rPage=/privatelabel/listing/photo_gallery.jsp?slim=pp285692&lang=en&units=Feet&id=2348368&back=/privatelabel/listing/pl_boat_detail.jsp&boat_id=2348368

[PeteW]

Great job putting that system together from parts. I'm totally impressed. You have confirmed for me that the BD-80 seems like the right size. Despite some stuff I've read, it still appears to be in production at Danfoss.

I have a lead on a pretty big SS Adler Barbour holdover plate that I can get cheap but will need to find a properly sized expansion valve for it. I noticed your plate has what looks like a thermostatically controlled expansion valve on it. I have no idea what to look for in that department.

Thanks again,
Pete W.

[RayNWanda]

The system is not hard to build. They send you a very detailed manual. Sometimes you are cutting pieces of wire and setting them aside, and you wonder why. A few steps later they have you take one of the pieces, put this connector on it, install it here. My biggest concern was my soldering experience. I got it put together and pulled vacuum on the condensor unit at home. It held vacuum overnight. So- once it was in the boat any leaks were probably elsewhere. At this point Dale fixed me up on how to run the refrigerant lines. They will go behind the stove easily. I had overlooked that place. I had a little trouble getting the system tuned for best efficiency. I conducted quite a few melt tests adjusting the mix in the plate. I finally got the mix to work between 2 and 10 degrees and called it good. I bought our system just before they went out of business. Our plate was only 2/3 full of mix. I added mix to cover the top tube in the plate. Then the mixture had to be tweaked. Of course, the goal is minimun run time, maximum down time. At the time we had 2 group 31 house batteries. We had to charge morning and evening for about an hour. I later upgraded to 4 group 31's and could go 24 hours between charges. It pulls about 7 amps running. It was an interesting project and I learned a lot in the process of getting it installed and working.
The expansion valve, do you size it for the plate or for the volume of refrigerant? I suspect it and the orfice needs to be sized for the refrigerant flow. That is what is good about the kit- everything is already sized to work together. The base plate is prepunched for all the components. You just have to tube it up and wire it. If you can get it together it will work. You will need to super tune it, but several of us here can help with that.

[Jim S]

We installed the CU 100 air cooled compressor and the 153 horizontal evaporator on Phantom in 2004.  The compressor is on a hign shelf in the port lazarette by the aft bulkhead.  The freezer will get to 19 degrees inside the evaporator box while maintaining a temperature of around 38 degrees  or lower in the rest of the box.  Run time in the hot summer is about 40% at 4.5 amps.  It won't hold ice cream but it keeps frozen foods frozen and makes ice cubes.  It is a nice compromise system that works well for us.  It might not work well for those who want a large freezer.  Items left directly under the evaporator will stay frozen.

The installation was easy with the lines run behind the range.  We use a remote temperature sensor from Radio Shack that we move around periodically to check different areas of the box.

[PeteW]

Thanks Jim,
The Cu100 is a BD50 Aircooled Danfoss. Your description of the performance you get seems to jive with the specs. It seems very acceptable. I believe the  Cu200 is the same compressor but with a water cooled option. Water cooling really does seem to help with efficiency if you're looking for more cooling with less current. My pathetic reefer was rebuilt by the PO  with a tiny BD35 compressor.  I'm not sure if at the end of the day that rig could even deliver a cold beer which is where  I'm afraid I have to draw the line.

Pete W

[PeteW]

Ray,
Your refrigeration system looks like the way to go. I priced out the Rparts kits with the BD80. (Around $1700). I also found an Isotherm ASU4901 that is almost identical ( BD80, watercooled, holdover plate) for $1420 on Ebay. Cheaper and minus the fun of DIY. But still more that I want to divert in funds at this time.

So I'm building my reefer system from basically junk. I scored an NOS AB eutectic holdover plate with 2 circuits. 30% bigger than that the C plate you have for under $200. And I found the TN2 adjustable expansion valve from a guy in Alabama. The second circuit in the plate could be plumbed to an engine driven compressor so I'm told.

Since the DB80 with control module will be around $700, I'm going to try something else. I have one BD35 and I can get another with controller for <$200. So I will run them in parallel. I don't know much about refrigeration but I'm learning and I think all I need is check valves combining the 2 high sides. I can run both or 1 for power savings.

My box, as yours has that sliding shelf. So instead of side by side freezer/refrig compartments. What do you think about making the lower half the freezer and the top will be the refrigerator. I could duct the holdover plate toward the bottom half or actually put it in the lower half. Anybody have an ideas on this ?

Thanks,  Pete W old hull#6

[Dale Tanski]

Pete,
An ice box will naturally stratifies and be colder on the bottom.  The problem you may have is when the boat heels, the cold will heel as well and as the boat sloshes the cold will slosh mixing the ice box cold with the frig warm. 

As for the multiple compressors, that is commonally done on larger HVAC systems.  As the heat load goes up, they kick another compressor in.  They do have separate coils and controls for each ganged together.

Dale

[PeteW]

Dale,
Sorry to hear about your teak rail getting banged up. Still replacing mine piece by piece.

All the install manuals for systems with holdovers plates say mount it high up in the box. As you say cold air is heavier and it all makes sense. The sliding horizontal divider in my box should however act like a baffle to keep that cold air in place at the bottom in the freezer when the boat rocks.  Perhaps dual thermostats with the upper controller operating a fan would do the trick. I had a Kenmore refrigerator that worked that way with the freezer on the  the bottom. A thermostat conntrolled a fan that blew cold air up to the refrigerator.

The Isotherm Compact Dual compressor system has 2 BD50's. Its a way big system. Point is it has a single water cooled condenser and a single set of hi/lows lines going to a single hold over plate. So they combine prior to the condenser I think. Dual BD35s would be a little bigger than a BD80. But as cold as the water is in CA a single water cooled BD50 would probably work great. And it uses the same controller as the 35. 

Being from NY myself, I still have family up in S Wales NY that I visit.  Your property looks like that area.

Regards, Pete

[Dale Tanski]

Pete,

Wow, good eye, stop in!  South Wales is at the end of Rt 400.  We are outside of Wales Center about 7 miles as the crow flies north east from your family. 
Any time just E-Mail me for directions.  Boat will be in the water until Oct 15th.

Dale

[S/V Passage]

This is a helpful thread. We are looking at options for the non-functioning unit that came with Passage. We aren't sure if we want to devote amps (or $) to refrigeration in the long term...Does anyone know if there's a plug in the bottom so we could just convert her refer into an icebox? It looks like there is in the foreward starboard corner, but it doesn't seem to actually go anywhere...

[PeteW]

Since my refrigeration system  is currently being mocked up in the garage I have had to resort to using the box as an true ice box. With a block of ice its good for a couple of days.  Yes there is a drain. It drips into the bilge on my boats and will keep you awake. They say you should plug the drain as cold air will run out the bottom of the box. So I suppose that means put a valve on it. All in all, it works way better than an igloo cooler.

So far I have spent around $400 on parts to rebuilt what looks like what was  once Frigiboat condenser/compressor unit. Through ebay I got a huge Adler Barbour hold over plate ($150) and Danfoss TXN Expansion Valve ($90) and a new in the box Danfoss BD50 Compressor ($125). The BD35 is simply too small.  Also  few buck on ebay for a filter drier, receiver, some shraeder valves and sight glass and I'm ready to put it together. I'm sticking with the air cooled condenser from the old frigiboat plate for now. Also I re purposed the controller from the old BD35 to run the BD50 compressor which is why I did not go to a BD80. With the set of Aeroquip connectors I had  I can pump it down, charge it in the garage and dissable it for installation in the boat. We shall see.

Pete W.

[Dale Tanski]

Pete,
No matter where your ice box drain ends up you should/could install a trap just like under your sinks at home.  The purpose here is not to keep the sewer gasses out but rather provide a water block that keeps cold air from running down the drain tube. Make the trap vertical offset bigger to account for boat heel and the contained water draining out when that happens.
As for where the drain ends up, you can install a hand pump (small tube bilge pump) in the line and pump it into your galley sink drain and over the side.  Over the side is a better option than in the bilge.  Anything that spills in the ice box that ends up in the bilge will eventually smell and possibly grow.  Think over the side.
Thirty two degree water in the box from melted ice is thermal mass and beneficial, so do not be too quick to get rid of it unless it is damaging the contents.
Dale

[PeteW]

Dale,
Right, a trap. Thanks, I was having a mental block thinking that a trap blocks air in both directions.

I'm finishing up a little article for "This old boat" featuring my "dual bilge pump controller with hysteresis". Simply it shows how to assemble and wire up a time delay relay circuit to keep your secondary bilge pump running (or you primary pump if that's all you have) for a programmable period of time after the float switch has gone low. In my application the secondary  pump is a wale gulper that drains my bilge to the bottom of the pickup tube and runs long enough  empty the discharge hose. It keeps my bilge almost dry and can pump food particles or whatever collects down there. Also it draws no current in standby which took a little extra design thought.

Pete

[PeteW]

I'm in the middle of leak testing my home-brew reefer system. Finding leaks by pulling a vacuum is a bit time consumming, so I'm going to get a bottle of nitrogen. So far I found 3 major leaks.  A dent in the mating surface of the expansion valve where the orifice mates. 2. a male AN connector on my filter/drier and 3 a leak in the soldered pipe to plug the service port on the compressor.

Here's my question for anyone that has familiarity with the Aeroquip 5400 series reusable disconnects. My plan is  to charge and test the system on the bench and then break it apart and reassemble the evaporator system in the boat, pull a vacuum on that half and simply recharge that half before reconnecting to previously charged  condenser. My problem is that I can't pull a vacuum on disconnected Aeroquip connectors as they suck air when not connected to the mating half. Perhaps they only seal under pressure? In that case I will need a dummy pair of disconnects to evacuate the evaporator half. Anybody know anything about these?

Pete W