I installed a Carrier Ductless split (Outdoor M# 38HDF036, Indoor M# 40QNC036) about a month ago as secondary cooling for a sever room and have yet to get it to run correctly. I have 140 feet of line set with 20 feet of lift. I followed the long line guide to a T, putting the correct calculated charge (10lb 10oz total) in the unit and the correct piston size (66). Two days after it was running I found it with the evaporator completely frozen and both the suction and mixed phase lines frozen. I had to take out the freeze stat clean it and put heat conductive compound on it and got it working, but then it would cycle every 10 to 15 minutes. I was running 75psi suction, about 15 degrees. I removed the charge and verified I had the proper charge. I took out the piston and looked for debris and cleaned it, I replaced the liquid line dryer, I scoured the entire line set for a restriction and found nothing. I was still running 75psi suction. I finally added 3lb 8oz of R410a and got my suction up to 95psi but this is still only 28 degrees. I am not cycling the freeze stat every ten minutes, it is now about 20 minutes. I feel like I have exhausted every possibility I can think of. The kicker to it all is that another contract installed an identical unit to this one andit also is running 75psi of suction, they apparently don't care enough to get it running correctly.
If anyone has experience with these units any advice or direction on how to get my suction up to an acceptable pressure would be appreciated.