I have a medium temp., water cooled walk-in cooler which had R-12 in the system. I found the evaporator coil was full of holes, so I replaced the evaporator and txv, and after evacuating the system recharged with R-409a, as I was told this was similar to R-12, compatable with the existing oil in the compressor, only it operates at a slightly higher head pressure. I believe I have the problem with the system operation figured out, just was looking for some more insight. On start up my discharge pressure ran around 155psig, 96 liquid temp, sight glass was foamy, suction was about 58-60 with a 51 suction line. The box temp started at around 65 and after an hour to an hour and a half was at maybe 55. My water entering temp was 58 water leaving temp was 65. I removed one end of the water cooled condenser and tried to clean the water tubes best as I could, but cannot get the end plate to seal up, this is a tube in a tube type condenser with a square manifold on either end so you can clean the water tubes. After cleaning the water tubes my temps and pressures really did not change much, my discharge and suction went down a little but not much and my box temp. really isnt changing much. I have the head pressure control valve adjusted to the lowest head pressure setting either way I adjust the control the pressure and water temp stays about the same. I am in the process of getting a new condenser, and head pressure control. I believe the condenser is still scaled up to much to transfer the heat as this system is at least 30 years old and original except the parts I replaced. I thought I may be slightly low on charge as well but I pumped the system down into the receiever and after it had pumped down checked the liquid level in the reciever which was about 2/3 to 3/4 full of liquid. I did try to adjust the txv to increase the super heat, but also no changes occured, when I installed the txv I removed the head and internal parts wrapped it with a wet towel and soldered it in, so I know I didnt dammage the txv when I installed it, I know my sight glass was not clear but thought with 7-8 subcooling I should be able to get better readings than this. As I said I was looking to see if anyone else had any other ideas which I may have over looked. I have worked with 409a in the past on air cooled walk in coolers and had no problem, but this one I believe is running a little high on the high side pressure which is also causing the low side to run high and not let my box cool down better I believe if I can get my sub cooling up, get my water split up and my superheat up I believe this cooler will go for another several years.
Any help is appreciated!