View Full Version : R12 cold plate refrigeration

15-03-2007, 11:18 PM
Hope someone can answer my questions about my boat refer.
It is an R 12 system with two cold plates in series.
One Danfoss tev at the inlet of the first plate (brine solution) and the sensing bulb at the outlet of the 2nd (antifreze solution)
Sanyo 508 compressor with seawater condensor,sightglass receiver and fiter drier and finally a suction accumulator.
I recently noticed the suction accumulator and line ot the compressor was frosting at start up.
At start up low pressue is 20lb and high presure is 140 lb.
within two minutes low pressure drops to 10" hg and high pressure is145lb . Ambient about 70F.
I called a tech out to the boat he adjusted the super heat and said it was fine.The compressor is still running in a vaccumn.
The system has run fine for 8 years why would the super heat
suddenly need adjustementand is it ok to run a vaccumn?
Thanks Terry.

Pete the cool
14-04-2007, 03:12 PM
Hi Terry,
I'd probably start with pumping the system down and checking the tev screen(filter) .Then seeing if there is some spring resistance when you push the orifice into the body of the valve. If there is none and the orifice doesn't push back out slightly there that's probably the problem and the tev needs changing.
Pete the cool

14-04-2007, 03:27 PM
Hi Terry,

What is the superheat value?

As Pete the cool said check the TEV filter first. If it is OK then check the followings :

1- Liquid line filter drier
2- If there is a solenoid valve check it for partial blockage.
3- Check the refrigerant charge. Easier to measure the sub cooling. If it is between 4 and 7C then charge is OK. If sub cooling is low then there is a lack of refrigerant (leakage).
4- Check the TEV itself.
5- Evaporators. Any problem that doesn't let the evaporation take place. In this case the superheat would be low.

Good luck.