Independent Freezer/Fridge upgrade
Posted: Tue Jun 02, 2026 8:12 am
Our Cold Machine unit needed replacement and I remembered reading a 350 forum post from a owner who installed two isotherm units to better control the temperatures in the stock freezer/fridge design. The previous owner of our 350 did a great job insulating the freezer and fridge, so after evaluating our insulated freezer and fridge volume against our needs, we purchased two Isotherm 2012 units.
Installation was straightforward. The refrigerant tubes and thermostat wires fit nicely through the original conduit and connected directly to the two compressor units that fit nicely together on the stock plywood platform. We debated running another DC line from an spare CB on the main CB panel to keep the units powered separately, but the original wiring was robust enough to support both units with little voltage drop (we have a LiPo House battery providing a consistent 13 volts).
We connected 2' of ducting to the compressor fan shrouds to draw cooler air from lower in the bilge and reused the fan unit that vented the Cold Machines' heated "exhaust" through the starboard stern vent to do the same for the isotherm units. Bending the evaporator plates over a length of 2 1/2 PVC tubing was the most nerve racking part of the installation.
Initial draw on startup was 12 amps. We ran the units overnight and checked the results the next AM. The empty freezer was -2F at the bottom, 6F at the top. It was running at the time, drawing 3 amps. The fridge was not drawing power and was 37F at the bottom, 39F at the top. From startup (75 F) to when I checked in the AM (13 hrs), both units drew ~35 amps. Time will tell...
Installation was straightforward. The refrigerant tubes and thermostat wires fit nicely through the original conduit and connected directly to the two compressor units that fit nicely together on the stock plywood platform. We debated running another DC line from an spare CB on the main CB panel to keep the units powered separately, but the original wiring was robust enough to support both units with little voltage drop (we have a LiPo House battery providing a consistent 13 volts).
We connected 2' of ducting to the compressor fan shrouds to draw cooler air from lower in the bilge and reused the fan unit that vented the Cold Machines' heated "exhaust" through the starboard stern vent to do the same for the isotherm units. Bending the evaporator plates over a length of 2 1/2 PVC tubing was the most nerve racking part of the installation.
Initial draw on startup was 12 amps. We ran the units overnight and checked the results the next AM. The empty freezer was -2F at the bottom, 6F at the top. It was running at the time, drawing 3 amps. The fridge was not drawing power and was 37F at the bottom, 39F at the top. From startup (75 F) to when I checked in the AM (13 hrs), both units drew ~35 amps. Time will tell...