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Old 10-09-2008, 17:00   #1
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Location: Aboard, Pago Pago, Am Samoa
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Danfoss bd 50 question

I recently replumbed the discharge line on a new bd 50 through my water tank">fresh water tank, it's right up against the hull below waterline and only 25 gal and the danfoss is probably pumping no more than 225 btus. i'd do the math if I could, but I don't think there's a prayer of getting the water very warm. But my question is this, I've got the Danfoss at minimum rev, 2000, and when the system was slightly undercharged my clamp meter said 2.9 a which is in line with Danfoss's spec. Of course as the evaporator, in this case a big holding plate, cools the preasure goes down and the amps fall off slightly. I've now got it pulling 3.2 a and the higher i take the suction preasure the better it cools. At what point should i stop adding gas and simply put in the 1st resistor to run the compressor at 2,500 rpm? If it was an al evaporator i could time the frequency of the cycles, but it's a big holding plate. Has anyone out there run into this one? Clearly I didn't pop for the AES controller, I've seen too many dead ones. Also has anyone got preformance data for the old bd 2.5 i'd like to know how many btus it moved at 0 degrees? Can't find it on the internet. Thanks George
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Old 11-09-2008, 09:36   #2
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I can't answer your question directly, but on my previous boat (sailed in the tropics) which had a 12 volt water cooled system with a big holding plate, I just added refrigerant until the return line had a few inches of frost in mid cycle. It worked like a charm.
We could keep ice cream in the freezer.

Steve B.
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Old 11-09-2008, 14:23   #3
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Hey Steve Thanks for the input, that must have been a well insulated box, I've not seen 12/134a systems keep ice cream, only 502 systems. I've never had much luck getting a frost line out of a large holding plate, but that's exactly how I recharge al evaporators. It's time consuming but worth it. I'm dead thrilled with how the system is working, it's like getting free electricity. I'll probably try tracking down the resistor to raise the rpm of the compressor to 2500 and rebalance the charge. It's currently down cycling quite happily on the standard Danfoss t/stat at a setting of 2.5, it runs a lot but at a 3.2 a draw i can live with it. One of the problems is the t/stat is designed for an al evaporator and consequently has too large a differential, I used to readjust it after it started, but like I said at 3 a i can live with it. Thanks again George
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Old 11-09-2008, 17:22   #4
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A lot of places sell refurbished equipment, seems like that one just specializes in the sailing market.

Most "new" gear is never functionally tested, so in a sense a refurb is better than new because it has been tested, failed, cured, and retested again. If the price difference is right and the warranty is still decent, it can be a great bargain.

If the warranty is really short, it can also mean the manufacturer knows they have a turkey and that model shouldn't be bought at all, new or used.
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Old 11-09-2008, 20:40   #5
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George,
We had a 10 cu ft. box, about 20% was the freezer. The set points were adjusted electronically by me for +2 deg f to -6 deg f to match the cold plate phase change stuff. (Long story short, we got the cold plate ingredient from the inventors before it went mainstream and got licensed to a major company.)

We had a couple of vacuum insulation panels, one against the engine compartment and the other against the hull (backed up by foam for the curve). The system drew 17 amps for about 3 hours each morning.

We had a pressure water loop through the refrigerator for instant cold water on tap. Solar took care of all our electrical demands.

Steve B.
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