Hey everyone, I'm having some serious issues with a 10ish year old water cooled Liebert 1.5 ton unit. (I dont have the model/serial numbers with me as of right now, but if it will/can help, i can get them tomorrow) We have been fighting with this unit for a couple weeks intermittently. This building used to be a closed loop with glycol (unsure of the mixture/percentage of glycol/water), but is now an open loop.
About 6 months ago I ran a call at this same suite, diagnosed the txv to be bad, replaced it and installed virgin r22 with a new dryer, and everything was fine until a couple weeks ago.
My recent initial call out was due to a high head trip, an I found dirty inlet strainers upstream of the pumps (clogged solid with slime; believed to be a lack of maintenance on the building owners behalf). I cleaned the strainers for both pumps, reset the lockout, and everything was great for a couple of days. By 'everything was great', I'm referring to these numbers:
12 sub cool
15 sup heat
78 ent. air
59 sup air
60 ent. Water
90 lvg water
20# ent water to pump
43# lvg water at pump and ent. unit
33# lvg water from unit
Head pressure control operates normally.
Ref. charge is weighed in at 34oz.
A few days later, I received another high head trip. I verified water flow, reset the lockout condition, fired the unit up, and my numbers were all over the place, but the most consistent numbers I found were these:
20* sub cool
60* sup heat
12* temp drop across evap
28* temp rise across cond
Water pressures remained the same.
As the unit was running, the compressor began partially bypassing internally, cut out thermally, then would never reset. I let it sit over night with the power off, and the next day it was still open across 2 legs. The compressor was replaced the same day, and just to be safe, I replaced all of the internals of the txv. The filter drier was also replaced. This all happened the Friday before last. The unit was running almost identical to the first set of numbers I posted.
Last week (late monday, after the unit ran fine all weekend) there were some issues with the unit, but due to extenuating circumstances, I was unable to be the tech on site. The owner of the company and the vp ran the call and were baffled by what they were seeing. They spent 2 days out there trying to sort out the issues at hand. The numbers they were seeing were more like the second set of numbers I posted. After the unit was turned back on tuesday afternoon, it ran fine until we got a call this morning about another high head trip. They suspected the units' condenser was fowled, so after taking my base line numbers, I performed a coil cleaning. The base line numbers actually looked better than the post-cleaning numbers. As it stands now, I only have a 5* water rise across the cond. my head pressure starts around 235 and progressively gets worse. The unit acts as though it is pumping down. The head pressure slowly drops, so does the suction pressure. The sub cooling increases by about 3-4 degrees, and the superheat increases drastically, but slowly, never getting better than 50*. The distributor tubes gradually get more and more ice on them as the suction pressure drops. We have good airflow (pulling within .2 of the fla). There is no temp difference from the inlet to the outlet on the new drier, the condenser is clean, the water pressure has stayed consistently the same, nothing I do to the head pressure control makes the symptoms any better or worse. I'm at a complete and total loss here. The only thing I haven't tried doing is putting the txv bulb in my hand to see if it will change my pressures any. I doubt it will though, considering the suction line is 80*+. The unit is currently off to prevent further damage to the new compressor. Any help or feedback is greatly appreciated.