Refrigeration Upgrade

by Chick Lasser

Over the last 16 months I have been on what some people may call a “mission” to upgrade the refrigeration system of our 1995 C36 MKII Spendin Time. When we sold our last boat two years ago one of the “Gotta Haves” was refrigeration. Our last boat only had a thermo electric cooler and although it was better than an icebox it just didn’t do enough for us. During our search we actually bought a brand new boat that didn’t pass survey but that’s an entirely different story. What we did discover in our shopping process was that nearly all manufacturers were upgrading their refrigeration systems significantly, with separate freezers and refrigerators or at the very least individual compartments. Like the old saying, “how can you keep them down on the farm, after they have seem Paris’” we wanted that kind of system too. Well the shopping process lead us full circle and when we found a C36 that was doable we jumped, with the promise to my wife that “I can upgrade the system, NO Sweat!!!” What follows is literally hundreds of hours of work and research to make what I think is a very workable and well performing unit.

First things first, my first improvement was the installation of a vent into the cockpit locker to get some fresh air to the compressor and fan of my Alder Barbour Cold Machine unit. Next I put additional weather-stripping around the lids. This was done with Frost King 5/16x3/8 foam weather-stripping and then 1/2" Frost King angle seal at the counter level.

This worked better but I discovered I was losing seal from the gap where the lid hinges stopped. An easy fix with the 5/16 x 3/8 foam tape. During that first season we used the system as is, and although the little freezer compartment worked OK, the frig never got cold enough for us and the system was always cycling on. To keep fresh air moving into the cockpit locker we would put a small fan in front of the vent, but this took up counter space.

Before the boat was hauled in the fall, I set out to finish what I started. First I built out of 2” R9 vinyl covered foam, a divider to separate the two compartments. Photo #2 I can’t begin to tell you the time this took since nothing was square (welcome to boating) and it was all trial and error. After weeks of making templates out of 2” Dow Foam Board I was ready to cut the finished divider.

Next I ordered a spillover kit from Alder Barbour (AB) for $125, which included a colder capillary thermostat and spill over fan. This was installed and after a lot of work I fired her up. Much to my surprise and disappointment the results were mixed at best. Although the freezer section would cool down, I had a difficult time getting the fan to kick on to cool the frig. After numerous conversations with AB it was explained to me that the capillary thermostats work on a 13-degree cycle. In other words the fan would kick on at about 45 degrees and kick off at about 32 degrees. Needless to say the spillover fan would get the frig down to the low 40’s so it would never kick on and if I artificially got the fan to go on, it would never get cold enough to turn off. Not very happy with this to say the least. In my discussions with AB we talked about digital thermostats as an alternative but the quoted price was near $300 each so I wasn’t sure I would go that way.

Thank god for the internet. After a search I discovered a company that distributes digital thermostat equipment. After a couple of conversations with their tech engineer I was convinced they had what I was looking for at a fraction of the price. A credit card and a few days later I had my solution. Problem was my boat was now hauled for the winter.

Over the course of the winter I set out to complete my project. First I installed two muffin fans in the bulkhead to the aft cockpit locker. The upper one removes hot air while the lower one puts fresh air into the compartment.

I kept half of the passive vent so as to allow air to enter the locker while sailing. These fans are all powered with DC and do a pretty good job of keeping the locker fairly cool.

Next job was to crawl into the aft cabin and access the area outboard of the Ice Box. There I stuffed left over Dow Foam board cut into small sheets between the hull and the icebox. Additionally, I did the same under the icebox to prevent heat from entering from the bottom. To seal the sides I sprayed some foam insulation between the sheets of foam board, this helped fill the gaps. Note I did not do this on the bottom since I did not want to block this area permanently.

Now to the inside of the box. While at the Annapolis Boat Show I spent a lot of time picking the brains of the Refrigeration Experts and the consensus was to add insulation to the inside as well and to make sure it had a radiant heat barrier. To achieve this I had two challenges, 1. To find something rigid for the flat surfaces and 2. Something that was flexible for the contoured surfaces. After some searching I settled on 1/2" Green Board with a vapor barrier for the rigid square areas and Reflexix for the contoured areas. Both come from the building trades and are readily available. After installation I added about an additional R3.5 to what was already there, without sacrificing much room inside the box. Photo #4 shows the freezer area insulated, while Photo #5 shows the finished freezer compartment. Note: the drain area to allow water to flow under the divider. I insulated the refrigerator section of the box using the same system.

Some allowances were made to access the drain area, but all in all it was pretty easy to do. Lastly, I cut two sections of the Reflexix material to lay over each compartment while away from the dock.

With this all completed it was time to install the electronics.

By now I was convinced I wanted to trash the capillary thermostats completely and go all digital. This was for a number of reasons, but the most important one to me was the ability to program the set points and temperature ranges between on and off. With this said and another credit card bill, a second thermostat was delivered to my home. Mounting the thermostats was easy to do, but the wiring was another story entirely. After some trial and error and the help of my electrical engineer consultant it worked.

Final results: As I write this it has been working for a little over a month but the overall results look excellent and even better than I expected. Today it was 75 degrees outside here in Upstate NY and the unit is performing beyond my expectations. Under these conditions, the compressor is running for approximately 10 minutes out of every 36 minutes of operation, this translates into about 70% performance. At this rate my system will only be powered up for about 18 minutes out of every hour. When you factor in how much it ran before, this is a vast improvement and I have the luxury of a real freezer and a cold refrigerator. Today I kicked back and enjoyed a cold one in a frosted mug, munching on Hour dorves that my wife just heated up from our freezer. Does it get any better than this? Completed project Photo #7.

Epilog: Well now I’ve had an entire season with this system under my belt and with one minor change it worked very well. Since the cold air was being blown in at an angle I had difficulty dispersing the air throughout the entire refrigerator side of the box. I solved this problem by exchanging the louvered fan cover on the refrigerator side to one with just holes in it. This dispersed the air more uniformly and kept the box cold throughout.

With these changes on average I would say the system ran at about 60% efficiency over the course of the summer here in Upstate NY. This means that for every 100 minutes, the compressor ran about 40 minutes. Not bad considering that I kept the freezer in the mid teens and the refrigerator at 37 degrees all season.

As I write this article I am going to make some additional modifications to the system over this winter. First I am going to add some more insulation inside the freezer section. We had more than enough room for our needs and the added efficiency will be appreciated. I believe I have figured out how to install ¾” rigid foam insulation on the contour of the outboard side of the freezer. I will also add additional insulation around the upper ledge of the freezer. With these improvements I believe I will have a real workable system. Them I’m off to my next project, “Installing a Shower Stall in the Head”!!!