We've had a little time now to monitor the freezer and here's our report. With the freezer half full with frozen goods, and at a steady state, with the temp set to 10 degrees on the digital thermostat, and ambient temperature around 78-81 degrees, we timed the operation for a couple of hours and made the following notes:
1. Normal temperature stays precisely between 10-12 degrees.
2. Average run time is around 11.25 minutes on and 8 minutes off, though in the middle of the day (at around 82F ambient), the run times extended to about 13 minutes on and 8 minutes off.
3. The Smart Speed Controller normally runs the compressor at the lowest speed and the system consumes 3.1 amps at that speed while running. (using our Link 2000 amp meter).
4. Average amp usage per hour is 1.82 amps per hour, making for a total estimated 24 hour consumption of ~45 amps.
In a different test, just checking the Link 2000 amps used overnight with almost nothing else running on the boat, we used 15.8 amps from 11:30 pm to 7:30 am. This translates to 47 amps on a 24 hour basis. Ambient temps in the boat were 78-80.
We do not yet have a ‘run time’ meter on the compressor, but this would be the best way to monitor how things are going without watching the cycling of the box. The compressor is so quiet that it’s hard to monitor unless you’re sitting right in front of it.
Our freezer space, located under the dinette table, has dimensions of 20.5” long x 12.5” wide x 22.5” deep for a total freezer volume of 3.3 cu ft. There is 3” of ‘blueboard refrigeration foam’ insulation all around except 2” on the top. This equates to ~R22 insulation (using Nigel Calder’s figure of R6.5 for the blueboard and a few R’s for the wood) except about R15 on the lid.
Net space gain in the freezer by Frigoboat conversion: ~.85 cu ft (from removing the bulk of the holding plates). This increased our ‘usable space’ in the freezer by about 40%.
After we recorded the statistics above, we used our handy-dandy Laser Digital Thermometer to check the temperatures in various parts of the freezer, and found that we really didn't need the thermostat set to 10 degrees. We have since nudged it up to 18 degrees. This should reduce the run time a little, and still keeps everything hard frozen.
You should be monitoring water temp too, since it's a water cooled unit (keel cooler) the water temp will have an affect on how well the unit can transfer heat. (John on Nakia)
ReplyDeleteDave and Sherry
ReplyDeleteThanks for a great blog. I followed your example with the Frigoboat system and was waiting patiently until you installed yours. Thanks for the education.
Gerry