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Old 15-04-2021, 22:15   #1
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Upgrade old belt-drive system

Iíve been struggling with this problem for years: I have an old belt-drive system that is a current hog. Besides, it leaks refrigerant. For lotsa obvious reasons, Iíd like to upgrade. On the un-proven assumption that the coils and lines are sound, Iím thinking it should be possible to simply uncouple the old compressor, remove it and the drive motor, secure a Danfoss in, wire it, hook up the lines, get it charged and balanced, and Iím back to cold beer.
The existing system has R-134/Hotshot in it, replacing the R12 it was born with. The Google tells me that R12 is replaced with R134, so there should be no need to worry about oil compatibility, orifices, etc since nothing past the couplings would change, including refrigerant.
I of course would get a qualified refrigeration tech to do this?
What am I missing? How have I over-simplified this?
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Old 15-04-2021, 23:32   #2
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Re: Upgrade old belt-drive system

The various refrigeration components, evaporator, compressor, condenser, pipe sizes (to ensure correct velocity and therefore oil return etc) must be engineered to compliment each other, otherwise you will only create another power hungry, troublesome situation.

Strongly recommend you dispose of all the existing equipment and replace with a new DC system selected after having a 'Heat load and Power consumption estimate' done on your cabinet to enable choosing the most suitable equipment for the job and to provide you with a guide as to daily power requirements.
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Old 16-04-2021, 06:31   #3
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Re: Upgrade old belt-drive system

The shaft seals all leak.
I assume you have txv's and eutectic plates.
Oze has it correct.
Start from scratch.
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Old 17-04-2021, 07:32   #4
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Re: Upgrade old belt-drive system

Quote:
Originally Posted by Mickeyrouse View Post
Iíve been struggling with this problem for years: I have an old belt-drive system that is a current hog. Besides, it leaks refrigerant. For lotsa obvious reasons, Iíd like to upgrade. On the un-proven assumption that the coils and lines are sound, Iím thinking it should be possible to simply uncouple the old compressor, remove it and the drive motor, secure a Danfoss in, wire it, hook up the lines, get it charged and balanced, and Iím back to cold beer.
The existing system has R-134/Hotshot in it, replacing the R12 it was born with. The Google tells me that R12 is replaced with R134, so there should be no need to worry about oil compatibility, orifices, etc since nothing past the couplings would change, including refrigerant.
I of course would get a qualified refrigeration tech to do this?
What am I missing? How have I over-simplified this?
There are a number of reasons why your plan will not work:

The box on that boat even new was not designed for a small 12 volt refrigeration system that is probably why the larger belt drive unit was used.

A Danfoss BD 12/24 volt compressor is not compatible with any part of the old system.

The oil and other contaminates left after flushing are a serious problem for compressor's new oil not to mention how to cool a hermetic sealed compressor.

The only technician you would find to follow your up grade plan would be skilled in Hell.

The advise given to replace complete is good but do not expect much from small 12 volt systems unless the system manufacturer will post a cash performance bond.

Questions
Do you know many amp-hrs a day the old unit consumed?
What temperature was the old system set to maintain in box?
Was there ever condensation on box's exterior ?
I assumed the old system was water cooled ?
I also assume Gulf Coast cruising water temperature?
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Old 19-04-2021, 04:46   #5
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Re: Upgrade old belt-drive system

When my box was new ( 1973) I donít think the Danfoss hermetic 12 v compressors were on the market- refrigeration of any kind on yachts was extremely rare at the time. Iím convinced of the incompatibility of my proposal, but donít understand quite why yet itís so just yet. This is branching off into the hypothetical at this point, but it seems if a new compressor is designed to run on R-134 and itís related oil, and if thatís whatís in the system at present, Iím not grasping the conflict. As far as cooling the compressor are itís needs any greater the present set up? There is certainly room for a fan.
In other parts of the question, Iím starting to accept that the other copper parts of the system are probably getting brittle and would be leak-prone. After all, this reefer has seen 48 years of service. It worked well when she worked- kept ice cream hard in Florida summer.
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Old 19-04-2021, 04:56   #6
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Re: Upgrade old belt-drive system

Old system was not water cooled, and would draw 36 amps at start-up, setting down to 21. Condensation only started forming recently. Kept ice cream hard in Florida summer.
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Old 19-04-2021, 08:09   #7
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Re: Upgrade old belt-drive system

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Originally Posted by Mickeyrouse View Post
Old system was not water cooled, and would draw 36 amps at start-up, setting down to 21. Condensation only started forming recently. Kept ice cream hard in Florida summer.

A better solution for you if your problem is normal loss of refrigerant over time common on that age of systems is to remove refrigerant from system FIRST. Then with no pressure in system check oil level in compressor if low add Castrol iso 100 refrigerant oil to proper level and re-service with R134a without additives available at Walmart. Correct refrigerant charge on that unit is around 18 normal amp draw. Hotshot is a blended refrigerant serviced as a liquid and is not recommended for a system that might loose small amounts refrigerant over long periods of time. Yes, I know this method goes against the rules and today's standards. What have you got to lose when you except the fact your present 1/3 HP system could not function with a 1/12 HP Dunfoss compressor. A boat's insulated refrigerated box as old as yours 1/3 HP refrigeration may be necessary.
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