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Old 22-03-2015, 07:41   #1
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DIY Smart Non Destructive Refrigeration Knowledge


I have been asked many times over the last 30 years to recommend a repair person experienced in repair of pleasure boat refrigerators. These days there are over 100 different fractional horse power 12 volt refrigeration configurations in boats under 50 feet. To find a person with experience on all small refrigeration units is not possible. There are no licenses available to qualify a person to accomplish a repair to a malfunctioning small boat refrigerator. Manufacturers specific training on each model or previous experience is necessary to repair these small 12 volt units. Each week I see where a so called HVAC trained technician or an Automobile AC mechanic screw up a good small pleasure boat refrigeration unit do to theirr lack of the right knowledge.

I have spent sixty of my eighty years assisting mechanics and operators of equipment in Do It Yourself troubleshooting and repair. Most of the time DIY is the only or smartest way to keep something operating. If a boat owner understands a few simple facts he or she can save on costly repairs and in many cases avoid purchasing a new refrigeration unit. Before allowing anyone including yourself to touch a malfunctioning refrigeration system powered by a Danfoss 12/24 volt BD compressor you should know these facts:
· If This BD Compressor does not run it is because the control module sees and electrical current out of normal limits and to protect compressor from an internal failure control stops compressor. After electronic control module detects amperage loads or voltage out of predetermined limits it will stop compressor from running until problem is corrected. After stopping compressor module will attempt a restart every 40 seconds to determine if problem is corrected.
· Most important trouble shooting item to remember about Danfoss BD compressors is, If compressor will not run problem is electrical. Only if compressor runs with little or no cooling is it safe to assume refrigerant volume or its flow is the problem..
· Danfoss BD compressors manufactured after 1995 are three phase variable speed allowing balancing of system performance reducing energy consumption. These compressors are identified by model numbers BD35, BD50 and BD80 they also have ability to identify problems by an LED fault code if compressor fails to start up and run.

LED will or will not show all problems. There are things you should know about Danfoss BD refrigeration that most repair people don’t know about your Adler Barbour , Frigoboat or other type refrigeration units. This applies to Danfoss BD compressors installed after 1995. Troubleshooting the newer Danfoss variable speed BD compressors when equipped with troubleshooting LED is easy if the following information is understood:
ü LED will not signal if there is no power to Danfoss Control module.
ü LED will not signal if thermostat circuit is open.
ü LED will not signal if compressor is running continuously with poor or no cooling.
ü LED will not signal if system is low on refrigerant, compressor will run with little or no refrigerant and still no LED signal.
ü LED will flash 3 times every 4 seconds if there is too much refrigerant in system or poor condenser compressor cooling.
ü On Adler Barbour CU100 and CU200 LED will not flash when compressor stops do to a problem inside the add on stainless box. This seems to be caused by poor solder connections to fuse holder or cracked printed circuit board. See my TECH TIP #1 on my web site.
ü If no one has tampered with refrigerant and refrigerant flow is blocked, compressor will not stop nor will LED flash on this type system. Common problem on Frigoboat keel cooler systems when refrigerant flow is restricted. Adding refrigerant will only cause additional problems. Ask Frigoboat US for help.
ü If there is too much refrigerant or contaminated refrigerant compressor will not start or run signaling with Three LED flashes.
ü Unlike automobile computers Danfoss electronic modules micro chip only has space for one trouble memory. Because only one memory is all that can be stored it is possible for a second problem to mask over signal covering up the first LED signalcode. Say the first signal is do to a low voltage giving a one LED flash every 4 seconds, compressor will stop and try to restart in 20 to 40 seconds. If refrigerant pressure has not equalized in this short off cycle a restart attempt can cause a three LED flash signal indicating an overload. When a three LED flash is indicated always confirm it by turning refrigerator power off and while watching LED turn power back on. The first seen signal code is where the problem is.
ü A faulty ground between module and main battery buss has been known to signal 3, 4, and 5 LED codes.

· Low or no refrigerant at all will not prevent this compressor from running.
· Because this compressor is silent the only way to confirm it is running is it will be warm to the touch after it has been running for 20 minutes or longer.

· Very rarely will you find a service tech who will take the time or be able to service these small units with refrigerant correctly because variations in ambient air or water temperatures as well as system design affect refrigerant charge.
· Service technicians and helpful friends rarely practice non destructive testing when they first approach a refrigerator problem. One way to know if someone does not know what he is doing is if he wants to check refrigerant pressure. Tampering in any way with refrigerant on these small systems that my hold only from 3 to 4 ounces of refrigerant generally leads to disaster us conditions at some point in the future.
· It is important to know these that small icebox conversion units are not mass produced in a quality controlled atmosphere like standard home refrigerators. Rarely are their filter/dryers large enough to capture additional moisture over what was generated in manufacturing process. There is always a risk of moisture contamination when tampering with servicing ports. Even purging gauge sets with refrigerant before use will not eliminate all osmoses imbedded moisture from gage set hoses.
· Danfoss BD compressor Ice box conversion refrigeration systems will not lose refrigerant if properly designed and installed correctly. The exception to this fact will be when line connecter O rings are used as final refrigerant seal.

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Old 23-03-2015, 11:33   #2
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Re: DIY Smart Non Destructive Refrigeration Knowledge

Thanks for that Richard. As an irredeemable DIY'er this information is invaluable. I will print your post and add it to my refrigerator's manual.


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Old 23-03-2015, 14:42   #3
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Re: DIY Smart Non Destructive Refrigeration Knowledge

Great Post Richard!

Just this weekend I had a call from a client that was perplexed after having a local Key West Florida refrigeration tech come aboard and tell him he needed a new compressor on his refrigeration system. The tech saw the flashing 3-LED error code and announced that, “well that code means the compressor is failing to start. That means it is dead and needs to be replaced.” The price to install a new compressor was quoted at $1000 ($500 for the compressor and then $500 for labor) but fortunately the client called me to ask a few questions and 30 minutes later we had his unit up and running. Turns out the day before he had installed a new alternator and in the process had loosened up the DC ships ground. Bingo…that was all it took to cause a voltage drop on start-up large enough for the controller to kick out and give the 3-LED error flash. What amazed the client is that he was watching both his ships DC voltage display and a hand held volt meter and he said he never saw the voltage drop during start-up. But as Richard has often said before, unless you have “superman eyes”, you can’t see what the controller sees!
Rich Boren owner of:
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Old 23-03-2015, 14:49   #4
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Re: DIY Smart Non Destructive Refrigeration Knowledge

We used your recommendations when we couldn't get a refrigeration guy to call us back. Now we have new wiring, an added resistor, a new thermostat and a full charge of R134. Unfortunately, we think the most important part of the equation is going to be to rebuild the box sooner rather than later. Only the coming summer weather will tell how soon.
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Old 23-03-2015, 16:41   #5
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Re: DIY Smart Non Destructive Refrigeration Knowledge

Originally Posted by Gisle View Post
I've edited all our buttons today. Some of you will have to press the reload button in your browser to see them right.
Fault codes are inherently problematic. You always have to go back to the basics. Electrical, mechanical and fluid engineering basics. Every system follows the same physical laws.

As the OP explains. No one person can be expected to know all the intricacies of every system. But a good refrigeration mechanic can always work from the generic to the specific.

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Old 23-03-2015, 18:05   #6
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Re: DIY Smart Non Destructive Refrigeration Knowledge

Valuable post thank you!
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Old 28-04-2015, 22:54   #7
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Re: DIY Smart Non Destructive Refrigeration Knowledge

Thanks Richard,
Great post AGAIN! Haven't logged on for a while, but will be back posting soon with photos of my rebuild.

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