Data Aire Problems
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.
Your motor amps are a little high. They should never be full load, unless there is a problem with the motor, I would expect to see the amperage 1-2 amps lower on each phase.
This leads me to think it is not the supply air flow that is the problem but the return air. How much return air area do you have? With a return air temperatue of 75 degrees I would not expect to see you icing up unless your undercharged.
You do not mention what the supply air temperature is.
I hope this gives you some ideas on what to look for.....
The problem is data aire, the plenium design is not correct so the fans have no static regain, which means you are not running enough air threw the evap coil. Turning the fan speed up WILL NOT HELP, this in combination with a scrambled evap coil they are using. That is why your pressures are great with one circuit running. That one circuit running has the whole coil to itself to pull heat out of the room, so when you turn the other one on your suction drops. Another thing to look at is the supple grills themself. The top of the grill blows air out and the bottom of that same grill sucks air in. I bent some sheet metal up to block about the bottom 1/3 to help that stop. This helped my suction a little.
hope this helps, I have a data center with 2 of these units. And I have the same problem
As far as your return air temp, 75 is impressive, check all the way around the unit. I wouldn't be suprised if you have mostly 65-70 degree air coming in. Also you may want to make sure your line set is correct, because if they made the Liquid line too small, you will have to deal with that.
do things right the first time is cheaper.
Could it be I don't have enought return? The unit is sitting 5" away from the sheetrock wall from the back of the unit. The side of the unit where the blower is has about 12" of clearance. The front has plenty of clearance.
We have had problems with downflow units,(on raised floors), with over amping. The problem was caused from not enough static pressure, (fan moving too much air). The people in the computer room had a bunch of the perforated floor tiles, adding them as they seen fit. They did'nt know they had twice as many tiles as they had air. If your motor amps is high, I would look at pinching off your supply. Could you be moving air over coil too fast for proper heat transfer?