The Food is Cold! Digitally!

Well, I finally finished another project.. This time it was an upgrade to the freezer and refrigerator on Mobert.  You may recall at the last haul out in November 2014 I had a keel cooler installed for the fridge compressor (the freezer already had one) and I disconnected the compressor air cooling fan.  The keel cooler is more efficient than air cooling.

The next step was to upgrade the controls and thermostats to make it easier to monitor as well as more automatic.  The old mechanical thermostats are marked 1 through 7 and effectively control the temperature of the evaporator plates, not the box temperature.  So first you don’t actually know what plate temperature each setting corresponds to AND you don’t know how that translates to the temperature of the food.  It was time to fix that.

Since we have Veco Frigoboat compressors I ordered their Merlin II automatic compressor speed control unit for both compressors and the Guardian digital thermostat units through Coastal Climate Control.  I spent quite a bit of time trying to figure out where to mount the two Guardian displays (one for each compressor) and couldn’t find a good place.  I eventually settled on using an open space in the Nav Station that was big enough, but required me to make a custom mounting panel as well as run a longer custom wiring harness.  Over the past few months I slowly worked on that project, using a Dremel to route out openings in a piece of plastic panel, making waterproof self-adhesive labels for the controls, and ordering a length of the 7-conductor cable that the controls came with in order to get the length needed to properly route the cables through the boat.

With the new custom panel made, it was time to cut the nav station hole and run the cable.  I used two different size wire looms to protect the cables from chaff in different areas of the run.  Getting the cables to the freezer compressor under the galley sink was relatively painless but the fridge compressor is up against the starboard side under the range/oven and there was no accessible pathway to run a cable under the floor.  The only feasible option ended up being to drill a hole through the stingers to pass the cable into the space under the compressor.

Mobert has Kevlar mixed in with the fiberglass in some locations and apparently the lateral stringer I needed to drill first was one of those locations.  I pretty much destroyed a brand new drill bit getting the first hole drilled.  Luckily the second stringer did not have Kevlar in it and the hole was drilled in seconds.  With the holes drilled and the cables protected and secured, I crimped on the connectors and used the heat gun for heat shrink.  It all powered up on the first try.   I reused the existing thermostat wire that went from the box to the compressor for the Guardian’s temperature sensor rather than trying to run a new wire into the box.  I got it all wired and working without defrosting the freezer and the ice cream and ice it contained.  This was actually a pretty big feat.  I have digital thermometers in the fridge and freezer box still so I can compare those temperature readings with the Guardian displays.  Once I figure out the average delta I’ll go into the programming and adjust the value.  I also need to decide just how cold I want the freezer and fridge to be.  I had the freezer down to 0°F lately but we might not need it to be that low.