I am working on a Data Aire Crac unit upflow with side grills right off the top of the plenum. This is a dual circuit 20 ton Crac. The pressure are perfect when I run them induvidually. The pressures are 70/250 Super Heat 8-12 Subcooling 10 of 10 degrees on both circuits. My blower motor is a 5 HP 1725 RPM FLA of 6.7 and is running 6.4-6.6-7.0 actual amps. When I run the circuits together the pressure go to 50/225 on both circuits and start freezing in front of the TXV distribution tubes going to the coil. My superheat and subcooling remain the same. I have called Data Aire tech-support out of california but have been little help. I had (3)27X13 inch side wall supply grill and cut out another 2 because the tech-support guy told me it was an air flow issue. The filters are clean. My return temp is 75 degrees and the outdoor ambient temperature is 85 degrees. I have also calibrated the sensors on the unit to make sure they where reading correctly. I just inherited this Data Center and from the looks of it there have been many repairs done at the site. The unit I am working has an 08 & 10 copeland compressor. Before I started working on the unit one Circuit was severly overcharged and the TXV's where flooding the Compressor. Any suggestions. I am out of ideas.