Hints and Tips



SO40 Refrigerator Mechanical Upgrade

Copyright 2017 Karl D. Lahm


The Frigomatic refrigeration system that Jeanneau installed in Voyageur was effective, but its evaporator bin had little room to keep frozen items, to the frustration of the Admiral. As we approach semi-retirement and more long distance cruising, including that away from marinas overnight, we seek to make the boat as energy-independent as possible, while increasing our food storage capability. Reducing the refrigeration draw on the house batteries while accommodating frozen foods were last year’s steps in that direction.

I decided to install a system with a much larger evaporator bin and a refrigerant-to-seawater heat exchanger, which is inherently more efficient than the standard refrigerant-to-air heat exchanger. There are two product choices, one from Frigoboat and the other from Isotherm. I chose the latter’s SP-2551 “self-pumping” product, based on price, apparent ease of installation, and others’ positive experiences.

The first step is removal of the existing apparatus. The condenser unit is readily accessible, behind the removable vertical access panel underneath the galley stove. The unit is easily unsecured from the plywood panel which it rests upon. The connections between the condenser unit and the tubing going to the evaporator are readily separated, their internal valves preventing the loss of refrigerant. Removing the condenser unit revealed surplus refrigerant tubing coiled up and secured to the shelf underneath the stove. Releasing and unwinding that coil is necessary to facilitate its removal.

Removing the Existing Apparatus


The compressor thermostat wire and refrigerant tubing enter the icebox via a cutout in its outboard, aft corner. This cutout is packed with putty, to secure the refrigerant tubing and ensure insulation of the icebox. To change the evaporator and its associated tubing, the putty must be removed. This is not much fun, as you can’t see what you’re doing and must navigate almost entirely by feel. A mirror and a spoon helps in this effort.

Refrigerant Tubing Exit Notch inside Icebox                                   Putty Removed from Exit Notch

Once the putty is extracted, the evaporator unit can be dismounted and the refrigerant tubing pulled out from the icebox. Releasing the thermostat box before dismounting the evaporator unit is a good idea, so that both can be removed together. Do note that excess thermostat tubing is coiled up and attached to the icebox ceiling, to the left of the evaporator, and it must be released prior to removing the bin and thermostat. It’s also a good idea to pull a pair of strings from the space below the stove into the icebox, during the removal of the refrigerant tubing.

Through-Hull Replacement

The existing galley sink through-hull is removed and replaced by the new unit with integral refrigerant-to-seawater heat exchanger. Previous experience with paddlewheel assembly replacement had informed me of the challenge presented by the sealant used by Jeanneau at the factory. The Isotherm recommendation to “drill out” the through-hull assembly was followed. A wooden plug was pressed into the through-hull from the underside of the boat, while it was in winter layup. The bit of a hole saw was centered in that plug, and the existing assembly, as shown below, sawed out.

Through-Hull Wooden Plug & Saw Cut                                           Removed Sink Drain Through-Hull

Installing the replacement through-hull assembly was readily done, with liberal amounts of 3M 4200 sealant applied to the inside of hole in the hull. The Isotherm instructions call for a 2½” (63 mm) hole, but a slightly smaller one would be more snug.


Compressor Placement


If the replacement compressor unit was located under the stove, as was the last one, the refrigerant tubing connections would, at best, require access into the space below the icebox and, at worst, not reach. Instead, the compressor was mounted in the cabinet under the galley sink, near the refrigerant-to-seawater heat exchanger through-hull assembly. It takes up little space and did not interfere with the trash can that is attached to the cabinet door or the tailpieces exiting the galley sink.

Condenser Unit Top View                                                                Condenser Unit Side View

The most challenging aspect of the installation process was routing and connecting the refrigerant tubing and thermostat wire between the icebox and the space below the galley sink. At first, I looked for a pathway along the hull, but that was blocked by the engine to/from water heater hoses. The bottom of the galley sink cabinet extends below the icebox, providing a pathway to the aft outboard corner below the access notch at the top of the icebox. Two adjoining holes were cut in the outboard wall that divides the galley sink area from the icebox space, to provide access to the space around the icebox. Then a steel fish tape was used to pull strings from the galley sink cabinet to the space under the stove and then from there into the icebox (if you’ve done this efficiently, the latter strings were pulled in when the original evaporator bin and tubing were removed). Once tied together and pulled into place, these strings follow a reasonably direct path from the icebox corner to the galley sink cabinet right-hand bottom. Two sets were placed and used, one for the thermostat cable and another for the refrigerant tubing. The power wiring for the compressor is easily rerouted under the floor, along the hull, and into the cutout in the bottom of the galley sink cabinet.

Obstacles Between Hull and Floor                                                    Hole in Galley Sink Cabinet Starboard Wall

If you intend to place insulation around the refrigerant tubing, I recommend that it be placed before the tubing is pulled in and the evaporator bin mounted within the icebox. I managed to place it after the tubing had been routed, but the process and result left much to be desired. Still, it was better than nothing.

Connecting the System


Once everything is in place, the refrigerant tubing can be connected and the components neatened up. A short piece of foam pipe insulation was placed over the evaporator return tube, to minimize heat conduction between tubes via their brass connectors.

Tubing Connections, Forward View                                                   Tubing Connections, Side View


Inside the Icebox


To make the evaporator bin effective as a freezer without losing much of the shelf space up against the hull, an additional shelf needed to be fabricated and placed underneath that bin. This was cut from ¼” (6 mm) King Starboard and placed against the aft wall of the icebox, from the existing molded shelf to the front side adjacent to the sink. Small blocks, cut from larger Starboard stock, were mounted to support the shelf. Thicker Starboard material was contemplated, but the expected weight of the frozen items on the shelf are easily supported by the thin shelf.

Side View of the Shelf and Evaporator Bin                                         Downward View of Bin, Shelf, and Thermostat

The evaporator bin was attached to the aft side of the icebox, immediately above the shelf. The major challenge in its installation is accurate marking of the screw holes in the icebox wall to align with the holes in the bin. The two bottom mounting post/spacers fit tabs cut in the bottom of the bin. They are installed first, the bin mounted, and then the upper screws and spacers attached. Securing the bottom post/spacers in place with epoxy is recommended. It may be necessary to increase the width of notches in bottom of the evaporator bin to accommodate imprecisely located support posts. Dexterity challenges plague this entire process, since you really can’t see what you’re doing.

The thermostat was mounted against the port side of the icebox, near the evaporator bin. This made it readily accessible, did not require cutting any new holes in the cabinetry, and placed it out of the way, though its dial must be read upside down and backwards (the Admiral will just have to get over it).

Bin, Shelf, and Thermostat in Perspective                                          Whole Icebox Downward Through Hatch

Before closing up the notch at the outboard aft upper corner of the icebox, using spray-foam, the system was activated and cooled the evaporator bin effectively.

I was amazed at the simplicity of hookup and success of testing. Though this project, like most, took much longer than expected, we should enjoy its product for years to come!

Copyright 2017 Karl D. Lahm