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phorvati 15-05-2013 13:34

Re-filling Danfoss based thin plate system
So I built my system using Danfoss BD50 and a thin plate evaporator based on instructions and parts from back in 2007, and using Kohlman's book as a guide. These systems have capillary tubes.
This is now the second time I had to service it/recharge it. Seems that every 3 years I notice that my vertical ice trays are not frozen anymore. At that time i also notice that compressor discharge is not hot/warm to the touch. I am glad i put suction and discharge valves on it so attaching a gauge/service set is quick and easy. It takes about half of a R134a can that you can get a wallmart etc. I guess i should try to chase the leak(s) but I am just wondering if any other Danfoss/thin plate evaporator based fridge owners have had similar behavior.
Very soon after adding refrigerant, you can feel compressor output/discharge getting hot, and at the same time, frost spreading across more and more of the evaporator.
At the time of failure, valves were at around 100psi for high side and 1-2psi for low side. There was not alot of change in pressures after re-filling. Suction side went up to around 5-6psi. I left the gauges on for about a day after servicing just to see where the pressures end up. I put a glass moisture indicator and surprisingly its still green but it has some yellow in it, not that i would know what it should look like if it had moisture.
Could the fact that the boat has been winterized and fridge shut off for about 6 months every year since 2008 have something to do with it?

mayball 20-05-2013 16:10

Re: Re-filling Danfoss based thin plate system
Your do-it-yourself system from R-parts is generally a high quality unit. The leak on the system will probably be a problem until you locate and fix it. If you have a Shrader valve on the top of the compressor, that is the first place I would look for the leak. I don't know why that tap is not brazed closed, since the unit can be filled using the suction base valve. Check for any evidence of oil in the cap, a sure sign of a leak. If the base valves are snuggly back seated, they do not normally leak.

If the leak is on the suction side, as the Shrader valve is, then it will leak more quickly when the unit is shut down for the winter, since the suction pressure will be at its highest during all of that time.

If you did not run the unit for any significant length of time when it was low on refrigerant, it probably did not operate with the suction in a vacuum, thereby drawing in air and moisture. Your moisture indicator will turn from green to yellow if you have moisture in the system.

phorvati 21-05-2013 10:56

Re: Re-filling Danfoss based thin plate system
yes i do have that valve. Thanks. I forget if i brazed that or did BD50 come with that valve. If i did, then it would have been the first thing i brazed. likely the worst weld cause i was learning how to use the torch etc.

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