Flooding compressor

[Silverjwj]

I am working on a unit that has two compressors built in to one evaporate coil. So two circuits. Compressor one operates as usual and compressor two kicks on only when there's heat rise and the first compressor can't handle it. My problem is compressor one runs normal at 60 degrees,but when I set the temp to 40 compressor two kicks on and then compressor one starts to freeze at the suction line. I checked the super heat and subcooling and got 10 degrees roughly. So I'm assuming the charge is good. Also I assume this because I used a vtech which is very accurate. So it's not overcharged so I'm thinking airflow. It has a new filter and a new fan so my question is, it's about 70 degrees in the mill so I think the air might not be warm enough passing over the coil to change the refrigerant back to vapor. So there for I'm getting liquid in the compressor. This only happens when circuit two comes on and rapidly cools the coil. When circuit one runs by itself it goes away. Is there anything else I should look * The Txv's we get come preset, so I dont want to touch those until I know for sure it's not airflow issue. Any suggestions would be appreciated. I'm kind of new at this also been doing it for about a year so i have a lot to learn.

[Silverjwj]

It is charged with 134a

[Silverjwj]

Also they usually run at 60 I just set it to 40 for testing. So could it be cause my temps to low and ambient air isn't very warm to condense the refrigerant in the evaporater back to a vapor.

[heatseeker]

It is a two stage not two circuit system. Is this application for air conditioning. An air conditioner is not supposed to run at 40 deg nor 60 deg. thats too cold. Anyways if you don't have enough heat load on the evaporator then it will freeze if overloaded. what is the outside * What temp are you trying to keep in the *

[heatseeker]

I think he got fired

[Mr. fixit]

So did you get it figured * I'm for sure interested in how it turned out.

[Silverjwj]

Haha no I didn't get fired. I was off for the weekend and when I went back they told me they changed out the control box and shipped it. I feel bad for whoever got that unit, because that was a totally different issue then what I was trying to fix. Anyways. Besides airflow being my suspect, there was a hot gas bypass with a txv with the bulb on the suction line that interacts with the epr. Which will take liquid from the discharge line and put it as a vapor back in the suction line. That could have gotten cooked when put in. I work with alot of people who just build the units and test them and don't understand the importance of why a compressor shouldn't have ice on it. I could be wrong but I learned in school you charge liquid on the high side not on the low unless you have that thing in line with the hose ( I forgot what it's called) that changes liquid to a vapor when charging. Like I said befor I haven't been doing this very long so maybe I'm wrong. Thank you for your responses sorry I couldn't go more into detail about what was wrong with it. I'm sure I'll come acrossed more issues soon enough tho.

[Silverjwj]

Heatseeker...the control temp was set at 40 and the ambient air was around 70. These units are made to keep an area at 60 degrees. So that's what we put them at when were done testing. I'm thinking it was a combination between being set to low and my ambient air not being very high.

[heatseeker]

okay sounds like they get set in the field. What kind of units are *

[Silverjwj]

They are called morphos.