Liebert A/c unit with low suction pressure

[dbanker]

To any one who can help. I have a Liebert Computer room A/C unit dating back from 1984. I do not have the model Number. I am guessing it to be approximately 12 tons. Having trouble with compresor one circuit freezing after the TXV and low suction pressure. Liquid line pressure slightly low but not too far off. If I overcharge?? system suction pressure rises. Cannot find any manufacturer instructions, parts manuals, service manuals or labeling showing required R22 charge. I do have the model number of this unit but not with me. If anyone thinks they can help, please respond. Have tried every possible thing I can think of, including replacing liquid line dryer, TXV, and rebuilt liquid line solenoid. (Not sure what solenoid is suppose to do? Maybe can answer this too.) Did not replace head of solenoid though.
Last thought which I am awaiting on results, running a deep vacuum on cicuit one for 72 hours then will charge with clean new refrigerant.

[chemi-cool]

Why Rebuild the SV?

What is the head pressure? is it normal? Too low?
TXV filter, clean?

Evaporator fans, Working ? Fins are clean?

Check and compare amp drawing and pressures with the other circuit, you might reveal some news.

[Peter_1]

You don't need catalogs to know the right amount of refrigerant: charge it till you have proper SC and SH and that's it.
If you're not able to reach this, then there's something else wrong.

[nevgee]

It's an old unit and as Chemi-Cool points out ... is the evaporator air flow adequate, are the fins and tubes clear, check the air velocity over the coil face.

[thebigcheese]

is this a long unit and u access the compressors from 1 end theres 1 mounted above the other?

[Peter_1]

Where's the SV located?

If you measure correct SH and SC you can't overcharge and if so, you can pull it back to your refrigerant vessel.

Normally on these Liebert, there's a sight glass at the side of the compressor enclosure mostly vertically mounted.
What do you see in it?

We need numbers to help you, SH, SC, LP, HP, discharge temperature, ambient around condenser and in the computerroom.

Downflow units I suppose?

Proper filters , coil clean?

[dbanker]

Well,
Charged this morning and all is well. I noticed someone asking about the evap coil. Yes it was filthy. Cleaned it last week. Friend recommended sucking system down into deep vacuum as there could have been moisture messing with the TXV. This did it. I do however still have trouble where the compressor two in the circuit does not turn off as it should and stays running after the system satisfies. This is also after the condeser shuts down. This in turn trips the high pressure switches on this unit then shutting off this compressor. Safetys then need to manually reset. Will look into this more later unless someone has a liebert specific recommendation.

[dbanker]

Yes thats it!

[Peter_1]

Compr 2 overcharged, can't go in pump down because it goes faster in HP than LP ?

[thebigcheese]

is the solinoid valve closing to pump her down?