Last Updated: 06/21/2020
Note: We upgraded to a Frigoboat Danfoss/Evaporator Plate
refrigeration system in January 2011, eliminating the holding plates and a
lot of noise and aggravation. We now believe this is the best option
for marine refrigeration.
Despite what some salesmen may lead you to believe, designing an efficient refrigeration system on a boat is a most complicated endeavor involving myriad decisions and a significant amount of research in order to get it right the first time around. calder
Most refrigeration experts agree that a quality high capacity 12 volt holding plate refrigeration system with well insulated boxes is the most convenient, reliable and efficient system for long term cruising with a big refrigerator and freezer. Installing a system yourself for a reasonable amount of money that will cool large boxes for many years and that you can repair yourself is an entirely different thing from having a mechanic install an off the shelf system that is guaranteed for a year or two. The system described below is the former design.
My system has been
on the boat now for 12 years using the same major components.
The compressor, a Tecumseh HG 1000 is now 30 years old and still going
strong with only new seals and gaskets. In comparison Danfoss compressor based evaporator plate systems,
especially the air cooled ones, like those sold by Adler
Barbour and others are inefficient, easy to damage and have major
that cannot be repaired and must be replaced. They are better suited
for smaller boxes and short term cruising where you can replenish your
refrigerated stores more often (note: we actually upgraded to a Danfoss-based
system in 2011 and loved it!). Because these less
expensive systems do not use a holding plate with an eutectic solution they
cannot take advantage of the significant energy savings made possible by freezing and thawing this solution.
They also are not set up with a receiver and valves for holding the
refrigerant in the system while working on/replacing components, many of
which are soldered into the system making removal difficult.
Below is a list of most of the parts and equipment you will need to build your own bullet proof refrigeration system as I have. Rparts was a good internet source and the numbers are from an old copy of their online catalog (their website down as of April 2013). As they do not do phone business, some prior reading on your part will be necessary so you will know what you are looking for. Two great references are the Glacier Bay website and Nigel Calder's book on Refrigeration. Some of these parts are available from local refrigeration parts houses, like United Refrigeration, in major cities and also, of course, on the internet if you know what you are looking for.
Subsequent Note: Calder's Refrigeration book is a great reference, but it is becoming a little dated. The latest version of his Mechanical and Electrical Manual has more up-to-date information on the newer refrigeration systems, and should also be reviewed for a more complete picture of the current state of the art.
You can buy the compressor rebuilt from Joe at Polar Bear in Ft Lauderdale for about $150 or new from Rparts on the internet for about $500 last time I checked. This Tecumseh compressor has a cast iron block, is much more robust and will last much longer than any of the aluminum block models from York and others. I rebuilt my original and then bought a rebuilt unit and spare gaskets/parts just in case. The special ventilated compressor pulley is available from Blissfield, the company that now owns the rights to Tecumseh. The Leeson motor is available new on the internet from multiple sources for about $250. Buy the 3/4 HP model, not the 1/2 HP model which has no internal fan (see the Glacier Bay article on the 1/2 HP model on their website for a further explanation).
If you have
a large system with long tubing runs or don't use a generator while running
the system, you should
slow the compressor down so the electrical draw is equal to about 1/2 HP by
pulley size on the motor to 2". The long tubing runs and many
twists and turns are the limiting factor in how much refrigerant you can
push around the system in an hour, not the compressor capacity. This
in turn limits the amount of BTUs that can be removed from the plates.
It is important to balance the maximum flow capacity of the system with the
compressor output so that the compressor is not working too hard
against itself. This also reduces the amp draw and
thus improves the battery terminal voltage while the system is running.
In addition we net our solar panel output against the
refrigeration motor electrical load thus reducing the load while running to
around 20 amps or less if we have good sun.
So the first step was create a new freezer space under the main cabin table, built to allow plenty of insulation. The original CSY Walkthrough double box is now all a front loading refrigerator with over/under compartments. The new freezer is separate and top loading built under the main cabin table. The refrigerator is now 10 cubic feet and the freezer 3. See here for how I upgraded the old nasty insulation in the refrigerator, without spending too much money or having to tear apart the whole thing.
Both the refrigerator and the freezer have heat loads of around 3000 BTUs a day--a little more if in the tropics with temps in the 90s, a little less if in temperate climates. The heat loads of any box are easy to calculate if you have the cubic feet of the box and the average thickness of dry insulation.
The BTU capacity of a holding plate can also be calculated if you know the size of the plate in inches and the type of eutectic solution.
Use the heat load and holding plate charts available on the Glacier Bay website or from other refrigeration companies like Sea Frost, Grunert and Technicold. Crosby's brine plates are about 10 percent less efficient than glycol plates used by most companies these days but their freeze-thaw temps are much tighter. This is more important in the refrigerator box than in the freezer. So a brine plate in the refrig and glycol plates in the freezer would be optimum. Used SS plates are often available on the internet or from owners installing new systems for less than $100 each-new plates are now well over $600 each. If a used plate looks intact and is not leaking eutectic solution it is probably fine. Mine are all used plates, some of which are original Crosby on the boat and most dating back to the late 1970s.
And you can mix up your own glycol eutectic solutions which would allow you to use a freezer plate in a refrigerator and vice versa by just changing out the solution. See Nigel Calder's refrigeration book or ask on the internet for the proper mix with water. I used a 1 part Propylene Glycol to 5 parts distilled water mix for a 27 degree refrigeration plate and it seems to freeze at the right temp. That was from Clive at Sea Frost who also told me that 1 part PG to 4 parts water gives a 0 degree plate. Calder says 40/60 PG to H2O gives 0 degrees and 30/70 gives 26 degrees. Richard Kohllman, a do it yourself guru on the internet, has another mix. As with many things in refrigeration there is often disagreement among the experts.
From Edwin on
s/v Frog's Leap,
December 2016: Regarding the temperature of the freeze point
for holding plates filled with propylene Glycol, here is the engineering
We run the entire system for about 1.5 hours in the morning and the freezer only in the late afternoon for about 20 minutes. The daily current consumption is about 75 amp hours. The refrigerator is able to hold over for 24 hours, the freezer for 10. Because the freezer will only hold over for 10 hours we top it off in the late afternoon so it will hold over through the night. If I could get more/better insulation around the freezer it would do much better.
The current refrigeration system, as of 2007,
has the following modifications from what some of the pictures below show:
Note that we ripped out the old Crosby holding plate system and installed a Frigoboat system in early 2010. We are glad we did. The main difference is that the evaporator plate system is designed to keep the boxes at a pretty tightly-controlled temperature. The new electronic thermostat lets you precisely set the temp and monitor it easily. The compressors draw only about 3 amps each when running--much better on the battery than the 40 amp draw the Leeson motor drew. The total daily amp-hour usage is about the same, and with the holding plates removed, we gained a lot of box space.
When researching new refrigeration systems here are a few questions I would
-Ask exactly what the system large enough to cool your box is going to cost?
(Topica Post 02/08/2005) Don't pitch your old holding plates! If it is original Crosby, it is a stainless steel brine plate with steel interior tubes. It has a capacity to remove about 3300 BTUs of heat an hour. Today it would cost you more than $600 to replace. They have a very tight freeze-thaw temperature span and work very well in our large boxes. My refrig plate, which is the same size as the one you mentioned, is cooling our 10 cu foot refrigerator box for about 25 AH a day. (top)
(11 Nov 09 CSY Owners Post) Based on what I learned over the years, there
are two types of holding plate solutions in common use. Neither is a true
eutectic solution, that does not change temperature at all as it changes
state from liquid to solid or the reverse. The solutions are brine (salty
water) and proplyene/ethylene glycol.
Upgrading the insulation in the original CSY 44 WT upright refrigerator/freezer
When I first tackled our the project of re-insulating our refrigerator, I consulted with a refrigeration expert who had already refurbished two CSY's refrigeration systems. He told me that the first CSY he did, he opened up the box liner to check on the insulation, and found it totally degraded to the point of providing virtually no insulation. So he tore out all the old original box, and totally rebuilt it with new insulation. That was a big expensive project. On the next project, he instead used was refrigeration-grade (ie not Home Depot) foam-in-place closed cell foam to re-foam the insulation, without tearing out the box. I followed his instructions and have been happy with the results (and the cost/effort).
The procedure is:
(a) Get good refrigeration-quality closed-cell foam in spray cans. First read the directions carefully on the spray foam can and understand its directions and cautions (ie be careful because the foam expands SUBSTANTIALLY as it cures--if you don't allow for expansion, it can cause damage to your box).
(b) Take the front face off the refrigerator/freezer space (see below for details)
(c) Allow the box space to dry for at least a couple of days
(d) Drill 1/4" holes in the walls of your box, on about 9" centers, into which you will spray the foam. Probing these holes with a screwdriver, I confirmed that there was virtually no original insulation left around my box. It had all disintegrated and crumbled to the bottom. Alternative or additional techniques are to knock for hollow spots and/or look for 'cold spots' on adjacent walls.
(e) Start at the BOTTOM holes, and spray in foam slowly, until it starts expanding out the next hole up. Move around and to all the bottom holes first, then move up to the next set of holes. Wait until the foam stops coming out of the next holes up, before moving on.
(f) Use the same technique on the doors, ceiling, and facings.
(g) Once it is all cured, drill out each hole 1/4" deep, and plug each hole with epoxy filler, so it is watertight.
Using this technique, we
used 15 (spray paint-sized) cans in our original CSY WT refrigeration box.
I originally did this in 1998, and as of 2011, the foam still looks like it
is doing the job.
2. Using a heat gun, heat the laminate around the front facing. This loosens the glue holding the laminate on. Gently remove the thin laminate. This exposes the screws that hold the front of the box on.
3. Undo the screws and remove the front facing.
It should come out in one large section (see photos below).
While you've got the front facing off, remove
and rebuild the shelf between the refrigerator and freezer box while you're
at it. (Old pictures below, new picture just above in the 'Front
Facing' picture. I used Expanded PVC which is a lightweight but
sturdy plastic that shouldn't develop rot problems in the moist environment,
like the old shelf did.
One tool we use all the time for checking interior temps on the refrigerator and freezer is a Raytek Mini Temp Non-Contact Digital Thermometer Gun. With this little hand-held device, you 'shoot' any surface you want to take the temperature of, and it immediately indicates the surface temp of whatever you are aiming at. This is perfect for checking that your thermostat settings on your fridge or freezer are set properly.
It is also useful for checking the OUTSIDE of your box for cold leaks.