filters clean and belts adjusted properly? set point set to low for the load you have ? you mentioned when unit is down there is sufficiant cooling in the room . maybe the lps is just doing its job. hmmm
Ok i had more time to look at it, yes it had low suction pressure alarm. Seems like it pops up a couple days after i rest it. Yes filters are clean and belt is good. This Liebert has two comp's and when the one trips, it still satisfies the unit, set at 68 degrees 40% humidity. Theres four other units in the room. I want to change out the lps but Id have to recover 26 lbs of ref to change it out(no shrader) and it was just changed 2 months ago right before we changed the compressor out. (yes its a new comp).
Heres the weird thing that has me leaning toward the LLSV. Ok when I show up and find it with a new low suction pressure alarm, the said comp is off and the other comp is still running to satisfy the load. The comp in question wont come on till I reset it(breaker). So I turn it off at the screen to let the working comp pump down, then I turn the breaker off. When I turn the breaker back on, the comp in question comes on and pumps down.(like it didnt finish pumping down before the alarm) the other comp is off at this time.
Then I have to hit the "on" button at the screen. Both then come on and work great. If your understanding what I'm saying, could it be that when sometimes when it pumps down to shut off it takes to long and throws it into alarm??? ive sat there and watched it pump down several times and it worked great. Thanks.
The compressor pumped down after power cycle due to it just completely shut off on a safety and did not pump down. Another concern is that the unit is making temp at 68F with one compressor, which tells me that there is very low load in this room or around this unit. You said that the SP is 75 and the HP is 240. Suction pressure at that psi is way to high for that return temp. That would be around a 75-80F return temp. This is starting to sound like the unit is overcharge. If it is, then it could be hard for the LLSV to close down and prolongs the pump down proccess. I would expect to see a 60-65F SP at that return temp. Is the Sight glass on the Liquid Line flashing (bubbling)? Shouldn't be or if it is with with that HP(240), you got non-condensables.
Ok Im going with overcharged so far. Both site glass were full. The comp in question sp was about 74 and the lp was 240. On the other comp the sp is about 60 and the lp was around 200 I took about 5 lbs out of the comp in question. Now the sp is around 60 but the lp is still around 240 it didn't affect that much. Filters and condsr are clean and both comdsr fans are running. Another tech said that the 240 lp should be normal. Is it? Thanks
What is your OAT? 240 would be ok if your OAT is 80+. Head pressure on an an air cooled unit will be affected by OAT. I like the numbers on your other compressor. 200 is more reasonable for current conditions. you may need to remove more juice and adjust TXV to get it right.
The lps is factory set not adjustable. The site glass just started bubbling so I stopped removing ref. I think I'll pull it all and start fresh. But I did think I might need to adjust the txv. My OSA was about 76 that day.