Author Topic: Can I replace an R12 AB CU-200 Refrigeration unit with a newer unit?  (Read 4217 times)

heynewt

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Searching this forum I've found partial answers to this, but I'd like a definitive answer if someone has it.

I have an old A/B "Cold Machine" CU-200 with a dead compressor (yes, it's dead, had the control unit checked).  I'd like to buy one of the new "pre-charged" A/B CU-200 refrigeration units along with the fitting adapters to adapt my existing "one-shot" evaporator fittings to the new CU-200 "quick-connect" fittings.   In other words, I'd just like to replace the refrigeration unit instead of also replacing the evaporator.  The existing evaporator works fine, and a new one is $500, not to mention removal and installation headaches. 

Is this possible to do?  To simply replace the refrigeration unit half of the equation?   I realize the old one uses R12 and the new one will have R134a.  What do I do about the existing R12 refrigerant in my system?  How do I clean out, as it were, the old R12 so that when I hook in the new pre-charged unit it works without having to add refrigerant, etc.  Or does it even matter?  It seems this should be easy, but I've had a hard time finding anyone who's actually done it.

Robert

Richard

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ANSWER
I do not think your compressor is bad 99% of the time if a Danfoss BD compressor will not run and module is good problem is either in the boats electrical system or condenser fan is drawing more than one amp on your unit.

Test for 4 pin Danfoss Modules
 No start up troubleshooting 4 pin modules consists of the following:

1. Place jumper wire across thermostat terminals, Compressor still does not run.

2. Disconnect black fan wire from electronic module. Compressor still does not run after fan ground wire is disconnected. One of the 10 transistors in this fan fails it can cause module to prevent compressor from running.
 If  Compressor runs after black wire disconnected replace fan.
 
3. Run correct size and correct polarity fused jumper wires direct from a fully charged battery to module in order to bypass all boat’s wiring. Volt meter readings are of no value at module. Now if compressor runs there is a bad electrical connection somewhere in boats wiring causing a low voltage spike during compressor startup.
Compressor still does not run electronic module needs to be tested on another unit.

New condensing unit on old evaporator
 
New Super cold machine components are not the same as older R12 units. New condensing units have a Danfoss Variable speed BD50 compressor, new type line connectors and 134a refrigerant oil. It is not impossible for an experienced technician to remove old condensing unit and replace it with a new style evaporator. Where the problem comes in is connecting new condensing unit to old style Freon R12 evaporator. Here are the tasks involved when complete system is not replaced and other things to think about:
•   Why spend more than $300 to install a CU200 over a CU100 when the addition of water cooling option will probably destroy any energy improvement a variable speed BD 50 offers?
•   I do not think that Demetic (AB) will warranty their condensing unit when it is connected to an older R12 mineral oil evaporator.
•   Air cooled compressor condenser units are not life limited, I just sold a control module to a boater with a 30 year old Danfoss BD compressor system. The problem with change you are proposing is aluminum evaporators on these systems are life limited do to corrosion after the first 10 years.
•   Problem with proposed change is new condensing unit comes pre-charged with 134a refrigerant and Polyester oil. New type line connectors have a self piercing disc that ruptures when connected. Old AB evaporator connectors have quick disconnects that must be removed and replaced with connectors match condensing unit connectors. Before correct connectors are installed on evaporator lines old oil must be flushed out of evaporator. At least one of new connectors should include a servicing port so evaporator assemble can be dehydrated before connecting it to new CU condensing unit.
•   If this project is contracted out I estimate cost after servicing and fine tuning to cost around $1,200.

Richard Kollmann

heynewt

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Excellent, thanks so much Richard.  I actually bought a new module from you over a year ago when the compressor first failed.  Installation of the new module didn't fix the compressor, and I sent the new module back.  But the additional tests you suggest here are worth trying before I replace the whole system.

My thoughts are that the compressor failed, because it is installed (by previous owner) in the lazarette and the summer heat in NC, along with a failure of the cooling water pump (clog), caused heat failure.  Let me try the suggestions here, and then I'll re-think my approach.

Robert N.