Let’s face it, for many sailors the dream is to only sail where the butter melts , but only when we want it to!
Marine refrigeration in the tropics becomes critically important: to preserve our food for the duration of our tropical adventure, and to accomplish while using as little power as possible.
Simple enough right? Well, in practice is can be as long as you have a well insulated compartment . The important thing to remember is that insulation doesn’t just keep cold in, It also helps keep that tropical heat out!
Your refigeration system goal:
50% Duty Cycle
Refrigeration is actually the act of removing heat from your compartment , that's a little counter intuitive to how we typically think of the cold, eh?
To remove heat, ColdEh systems use a standard Danfoss BD35 compressor that at its lowest speed removes approximately 214 BTUs an hour consistently regardless of ambient temperatures (while keeping the evaporator plate temperature in your compartment cold at 10F).
For maximum energy efficiency your goal is to have your refrigeration compressor (that BD35) run only half the time or 50% duty cycle. If it runs any more than that, its eating up power reserves when it doesn't have to.
So why is insulation important?
(and how much do you need?)
If your refrigeration or freezer compartment is well insulated, it will keep the heat out and the cold in.
Ideally you want:
• R30 insulation for a refrigeration compartment, and
• R40 insulation for a freezer box.
At these ideal levels of insulation you need never to worry about your performance of your system.
If you use R30 insulation with your ColdEh system in an 8 Cubic Foot refrigeration compartment in the tropics at ambient temperature of 95F, it works superbly.
It's simple math: your ColdEh system removes 214 BTUs an hour. At 95F, that ambient heat is working to go into your compartment at 49.6 BTUs an hour. So, your ColdEh system (for this compartment size example) would be working at about 25% duty cycle (214/49.6) -- and operating very efficiently.
Of course, you will be opening and closing your compartment (reaching for a cool drink...) so your duty cycle will increase, but able to stay well within 50% duty cycle.
What insulation level can you achieve?
Use these calculators below to determine the level of insulation you can achieve (or already have if you are not re-insulating):
• Calculating the surface are of your box (use rectangular compartment)
• Calculating the heat load with different R values (use Fahrenheit for temperature)
Remember, the more insulation you have in your marine refrigeration, the better it will perform. If you achieve optimal insulation for your refrigeration and/or freezer compartment you will be able to travel anywhere and not worry about your refrigeration system being able to function efficiently in cold, moderate or hot climates. Ahhh… pass the butter, and the ice!
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