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Old 24-05-2014, 08:42   #1
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And More Refrigeration Problems

I have two Isotherm SP refrigeration systems on board -- one freezer, and one fridge. I love them. But the first year I had the boat (four years ago), the fridge stopped cooling well, and I had a local refrigeration guy look at it. He said no problem -- just a little low on gas. He topped it off and it worked perfectly for four years.

I'm now cruising in the Baltic, and have sailed a few hundred miles to get here, often on a significant heel. At some point the fridge stopped cooling well (would cool just a little bit, or if on a starboard tack, would suddenly start cooling full blast again). Meanwhile it was running hot and making strange noises. Not good, I thought.

I had a guy in Sweden look at it, and he said -- no problem, low on gas. And boy, is that compressor hot. He topped it off. It seemed to work fine. But this morning it wasn't cooling right for a while; now cooling fine again (we're on passage so maybe the liquid freon got stirred up again).

So what do you guys think? My understanding of practical issues of refrigeration is very weak. Maybe I killed the compressor letting it run low on gas and getting too hot? Or should I put oil in it or something?

The system uses Danfoss BD35F compressors, which I don't think are too expensive, so yanking it out and replacing might not be the end of the world. On the other hand, would be nice to revive the old one if there's any hope. It's only 12 years old or so and has not given any trouble other than the apparently pinhole leak (not worth chasing -- both the previous tech, and this one, said).
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Old 25-05-2014, 13:40   #2
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Re: And More Refrigeration Problems

There are a number of reasons why cooling could be erratic but I do not think compressor replacement will solve problem. Before service man cam to boat I assumed boat was at anchor or stopped anyway so at that time was unit cooling properly? Correct working condition would be indicated by frost covering 90% of evaporator’s surface area.

Compressors do run hot, so hot you can not keep your hand on them. when water cooled. Instead of fan cooled. Can you report amperage when compressor is too hot and Speed of BD35 F. With this information an overload condition could be eliminated as a cause of problem.

I find service men use the excuse that refrigerant volume needed to be adjusted in order to justify charging for a service call when they do not know what is wrong.
Tampering with refrigerant on a system that contains less than maybe 3 ounces will do more harm and complicate original trouble. If there was a leak and he did not find and repair it in a month or less frost line on evaporator will cover less of evaporator.

The conditions you report of good refrigerant flow at times and lack of cooling at other times could be caused by an electrical boat problem or Danfoss control module senses a voltage spike or an excessive amp over load. The BD35 compressor module has a built in logic microchip for trouble shooting does your unit have this LED?
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Old 28-05-2014, 00:32   #3
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Quote:
Originally Posted by Richard Kollmann View Post
There are a number of reasons why cooling could be erratic but I do not think compressor replacement will solve problem. Before service man cam to boat I assumed boat was at anchor or stopped anyway so at that time was unit cooling properly? Correct working condition would be indicated by frost covering 90% of evaporator’s surface area.

Compressors do run hot, so hot you can not keep your hand on them. when water cooled. Instead of fan cooled. Can you report amperage when compressor is too hot and Speed of BD35 F. With this information an overload condition could be eliminated as a cause of problem.

I find service men use the excuse that refrigerant volume needed to be adjusted in order to justify charging for a service call when they do not know what is wrong.
Tampering with refrigerant on a system that contains less than maybe 3 ounces will do more harm and complicate original trouble. If there was a leak and he did not find and repair it in a month or less frost line on evaporator will cover less of evaporator.

The conditions you report of good refrigerant flow at times and lack of cooling at other times could be caused by an electrical boat problem or Danfoss control module senses a voltage spike or an excessive amp over load. The BD35 compressor module has a built in logic microchip for trouble shooting does your unit have this LED?
Thanks for that. I can't get to the compressor to look for the LED.

I don't think it's an electrical problem because the unit runs and makes odd noises. And the freezer - on the same circuit - works fine.

After the first day,it's been working ok, although seemingly noisier than usual. We'll see whether it holds up for a while now.
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Old 29-05-2014, 09:13   #4
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Re: And More Refrigeration Problems

If your unit has a troubleshooting LED there will be a wire connected to terminal D on the Danfoss module.

Without the LED You can not eliminate electrical or compressor causes interrupting refrigerant flow.

There are many reasons for noises such as refrigerant flow variations, a single phase in compressor dropping in and out of compressor pulse and a weak or dislodged compressor support spring. None of these noises are something to worry about if LED is not sending a signal.

The best advice I can give you is make sure you have and install the LED and carry a spare Electronic control module on board.
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