Help with a water cooled Liebert
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.
Is the system dry? Did it pull down good when you changed comp.?
The system is dry and the vac was good.
You did mention the vacuum was good. But thinking about if your water cooled condenser is leaking water into the system the moisture will condense to a liquid and freeze up inside the txv. Causing it to slowly pump down once you have it off for a while it thaws restarts everything looks good. Maybe that's why once you pull the charge n dryer charge it up then in runs good for a while! Just throwing it out there But also 240 head with 60 degree water inlet temp head pressure is pretty high. Unless you have a head pressure control valve. You mentioned you cleaned the condenser coil, Keep us posted
There is a head pressure control valve.
We have considered moisture to be the issue, but have concluded that it isn't the problem. Typically, a compressor will not bypass internally until the head pressure reaches the neighborhood of 400psig. My gauge is on the discharge line of the compressor, an when the compressor began bypassing, the pressure didn't reflect that condition on the gauge. The old compressor bypassed internally, and the new one has as well. It seems like (and this sounds a little absurd) there is something, fluid in state, that is blocking the check valve at the discharge of the compressor; or at least partially blocking it. After the unit sits over night, it would fire up and run like a champ the next day. Today there is an exception to that. It ran great for about 45 min, then without warning, the dist. Tubes began to ice up, suction pressure remained at 65, and the head began to climb. It reached 325psi before I shut the unit down.
How close to the comp is your access on the discharge line?
Within 6". The high pressure safety is just down stream from the gauge port another 2" or so. After witnessing all of the madness that is going on here, I swapped gauges, just to make sure my gauges worked properly. My boss put his gauges on it as well, and it's consistently having the same issues.
Does it have a reheat coil? Is it a basic dx water cooled set up. The replacement of txv was it a factory valve? Or was it sized aftermarket? Maybe it's a little undersized and it closes up? How about leaving the sensing bulb hanging in the air and watching the pressures
Originally Posted by Isaac3384
Do you have hgbp on this system? Is there a solenoid valve LLSV or HGBP.
I didn't write the book I just read it!
There is no reheat, no humidifier, no hgbp, and no solenoid valves in this unit. It is as bare bones as they get. Everything in the system includes a compressor, high pressure safety, condenser coil, head pressure control, txv, evap coil, and a freeze-stat. Other than those devices, there is nothing in the circuit.
I had to leave today before I could watch the unit operate with the bulb off of the suction line.
The txv I installed came straight from the local Liebert dealer, and is identical in size. It is the same BBIVE 1 1/2 that came out with the same 43 VGA power cap assembly.
Wonder if there is someting from the old compressor lodged in the discharge line. Does that model 90 right out of the compressor? Good spot to get something stuck. Head shaker for sure.
Not questioning your brazing abilities however I've had new expansion valves seize up and form ice crystals restricting and closing off refrigerant flow completely due to being overheated when installed. Your may have taken the valve apart to braze it in but most techs do not.
You obviously have a major restriction in the system......