Irwin 31 Refrigeration
Sorry, I don't have any direct experience adding this capability. But, the insulation in my 1983 Irwin 31 box is not great. You should have 4" all around and I don't see much room to add insulation. I have a 4" foam pillow cut to lay on top of the box and I added 2" of foam to the cockpit locker wall adjoining the box and 2" of foam on the inside of the box. It really helps keep ice longer but unfortunately, it really cuts down the room inside available for the cooling coils.If you find a solution, let me know. I do have some general info on reefers that I can share and have copied below.HarryFREEDOM7.3 Refrigeration SystemsRefrigeration for Pleasureboats: Installation, Maintenance and Repair, Nigel CalderThe Perfect Box -39 Ways to Improve Your Boat’s Ice Box, by Spa Creek Instrument CompanyThe Box Book, Adler Barbour, IM Industries, Bulford, CTModern Refrigeration and Air Conditioning, Althouse, Turnquist, and Bracciano, The Goodheart Willcox Co., Inc.A refrigeration system consists of:Insulated ice box with 4-6” of closed cell insulationHeat transfer plates in the frige or cold plates with eutectic material to hold heatCompressor (typically ½ HP and above and belt driven or hermetic)CondenserExpansion valveRefrigerantBoats with almost constant engine use could use a constant cycling AC units.Boats with small (<1500 BTU/day) demand can use constant cycling DC units.Boats with <3500 BTU/day demand can use an engine driven cold plate system or a DC driven cold plate system with a high output alternator and solar or wind power.COLD PLATESDole Refrigeration Company, 800-251-8990Adler Barbour and GrunertCOMPRESSORSCompressors could be hermetic but generally are belt-driven. Most are auto air-conditioning compressors of the swash-plate design.Sankyo/Sanden 214-442-8400York 217-422-0055Tecumseh 517-423-8411Danfoss 201-529-4900CONDENSERSWater cooled condensers are 10x more efficient than air cooled ones. They could use a centrifugal pump, but more generally a rubber impeller pump like the water pump on your diesel engine.Packless Industries 817-666-7700Standard Refrigeration Co., 312-345-5400EXPANSION VALVEAlco Controls, St. Louis, MO., 314-569-4666www.rparts.com Complete line of parts for maintenance, repair and upgrades for all brands including Grunert, Glacier Bay, Marine Air, Sea Frost, Adler/BarbourRefrigeration Package ManufacturersAdler Barbour (Polarmate®)P.O. Box 308New Whitfield St.Guilford, CT 06437203-453-4374Grunert2000 N. Andrews Ave.Pompano Beach, FL 33069-1497800-327-3137Sea Frost, CF Horton & Co.P.O. Box 36Dover, NH 03820603-868-5720IMI Crosby/FrigoboatDistributorsGlacier Supply Companywww.glaciersupply.com800-588-4540Waeco’s Super Cold Machinewww.waeco.comSea Frost372 Route 4Barrington, NH 03825800-435-6708603-868-5720www.seafrost.comBD is compact 12V affordable conversion kitAnnapolis Cruisair, Inc.2124 Renard Ct.Annapolis, MD 21401www.annapoliscruisair.com410-224-0970 or 974-6136Consider a propane driven system like used in RV’sStandout Yacht FittingsIce Saver Blanket (saves battery power by insulating top of icebox)It has been reported that a boat’s Danfoss refrigeration controller can cause noise on radios and FAX machines. The microprocessor inside the unshielded black box emits broadband pulses. To stop this, create a Faraday cage by encapsulating both the compressor and black box with copper foil from Metal and Cable Corp. www.metal-cable.com or West Marine and ground to the compressor’s metal legs. It would also help to place toroidal chokes (Palomar Engineers, www.palomar-engineers.com) over the control wires that exit the controller and some close to the plastic controller box as well as to wrap the controller box with copper screen.