Liebert P66 adventures

[The Doctor]

Repairing a leak in one of two circuits. The one circuit is running alone, and the head is 210 at 30*OAT. It was not producing a steady subcooling, like it was hunting, if I remember right. Sometimes 20, sometimes closer to 40.

I adjusted the screw on top and got a 235 head and paid no further attention.
Later in the day I finished the repair and charged in the juice, knowing what these circuits hold to achieve the factory recommended subcooling with that control. Both circuits are running at this point.
The head pressure on my repaired one was just under 200, and I just had this notion that I wanted it higher, and would check SC later. turned and turned the screw but it would not adjust above 200 no matter how many turns...never checked the non-leaking circuit alone after earlier in the day.

So the next morning I headed on over to reset the reported head pressure call on the other circuit!!! Apparently it satisfied the repaired circuit and was running the other all alone.

Reset it and Sure enough, it would run high 300s until the second circuit achieved its little 200 or whatever, and then the head moved downward.

Yanked that p66 and installed a new and both circuits are at factory subcooling, and SH for that matter.

My question is regarding the -2 that is used for Liebert units. Is it intended to be not adjusted by the blue paint on the set screw alone??
Or is it rendered nonadjustable on at least one circuit? Someone started a rumor. That's why I'm asking...

And does anyone like the p266 with it's extra moolah in transducers? Will it work that much better for that much longer?

I never had more than a small handful of p66 issues anywhere along in a dozen years or so ?

Any one else know if they're intentionally that way or no?

[Iamclayman2000]

Liebert units are critically charged systems.
They don't recommend charging them by SC because of receivers and pressure controls in the system.
I would always weigh in the charge.
Name plates should give you unit charges and get line set length and figure out how much juice to put in.
Check with Liebert.
They prob dont want you to mess with it because it is engineered.
Not just your average units.

[ispip]

I have put in the P-266 in 2 locations, one on a Liebert and the other on 3 Data aires. They do work well so far. If you intend on deleting the air tempurature controls and letting the P-266 control them it takes awhile to dial in. So I recommend putting a schreader Tee at the roof so you can dial in the P-266 easier. These controls have not been out for very long, like less than a year. And the p-66 is going away. As far as your question above, don't mess with the pressure switchs in the P-66, They are set up for Liebert Spec. As far as subcooling Liebert use to say 1LB after clearing the sightglass. That usually works out to about 8-12 degrees subcooling at above 200 psi head.

[The Doctor]

I have put in the P-266 in 2 locations, one on a Liebert and the other on 3 Data aires. They do work well so far. If you intend on deleting the air tempurature controls and letting the P-266 control them it takes awhile to dial in. So I recommend putting a schreader Tee at the roof so you can dial in the P-266 easier. These controls have not been out for very long, like less than a year. And the p-66 is going away. As far as your question above, don't mess with the pressure switchs in the P-66, They are set up for Liebert Spec. As far as subcooling Liebert use to say 1LB after clearing the sightglass. That usually works out to about 8-12 degrees subcooling at above 200 psi head.
That answered my question, I think. I'm wondering if they disabled the adjustment capability.
FWIW, this is in a Heatcraft condenser on an ATS system. I put the word Liebert in the title because I'm working for a Liebert partner, or whatever they call us now, so we carry Liebert parts. The most senior tech in the company mentioned that the factory p66 is not intended to be adjusted, but I wanted to know because I used to read the Enquirer :)

Before using the p66, this company used an encapsulated fan cycling switch, and said if the glass was clear, it was overcharged. Those tech support guys are long gone, and they now are looking for 10-20 subcooling with whatever condenser you feel like throwing up there.