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Old 07-02-2012, 06:09 AM   #41
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with the long refridgerent*runs from the compressor to the eutectic plates, all runing through the engine room, must be very inefficient.

NOT at all, the refrigerant is delivered as a liquid to the TX valve on the eutetic plate.

The theoretical loss of pumping a liquid thru 25 ft of copper tubing vs 5 ft is too small to contemplate.

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Old 07-04-2012, 08:44 AM   #42
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Originally Posted by Aquabelle View Post
A key point not noted above is that Danfoss "12v" compressors, while very good and efficient, are highly sensitive to voltage drop. One advantage of the 110(240)v/12v dual power systems is if the vessel has an inverter, the fridge will be running on the 110v circuit....and the internal conversion to "12v" actually puts out more like 13.2v and so the fridge operates well. But if the 110v side of the 110/12 auto-switch fails (which they commonly do) OR if the fridge is 12v only, then the fridge is highly dependent on the quality of the 12v supply. Running the 12v fridge power to the fridge via a circuit breaker on the main breaker panel often ends up with long cable runs and voltage drops. The fridge will run but it won't get as cold as it should and cycle times will be longer and amp consumption higher. Best practice is to run a dedicated cable from the House battery (or nearby bus) directly to the fridge (with an in-line fuse) to avoid volt drop
I'm not convinced that that would be the "best practice". For starters, you certainly want (need) a convinient disconnect method. While removing the in-line fuse would disconnect the refrigerator, it would not be convenient in many cases.

I think the best practice is to check the voltage when the refrigerator is running and if there's an excessive voltage drop, find out why and correct the problem.

I would think (and hope) that the manufacturer of the refrigerator would take into account the possible voltage drop in the wiring when designing and manufacturing the refrigerator.
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Old 07-04-2012, 12:49 PM   #43
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Fair point on the need for a switch if the fridge isn't being maintained 24/7...but no issue installing this on a direct-connect feed, in a convenient place. At least two major fridge manufacturers, Vitrifrigo & Isotherm, DO recommend direct-connection and make the point about sensitivity to voltage drop. But I also agree the voltage should be checked while fridge is operating and obviously, if it is remaining above 12v then no problem. Many people will, however be surprised to find just what voltage drop they do have if they have long cable runs to circuit breaker board and then aft (typically) to a fridge. Even small drops make a big difference to "12" volt compressor efficiency: the fridge will still work (which is why many folks don't pick up they have a problem of this origin) but the fridge cycles longer and doesn't get as cold as it should.
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