nisong said:
CAN SOMEONE TELL ME,WAS THERE ANYTHING I DID NOT PROPERLY?
IMO your approach to the whole problem is off. You responded to a low suction alarm on the chiller and tried several ways to resolve the "symptom" - the alarm - without thoroughly considering the source of the problem, and why.
Adjusting the TXV was absolutely NOT the solution. There was also no need to adjust the refrigerant charge if you did not suspect a leak or if the charge had not been adjusted previously by you or another tech.
Your problem may be a lack of understanding the dynamics a refrigeration system experiences under low outdoor ambient temperatures. Why must condenser or tower fans be moderated or cycled when outdoor temperatures drop below a certain point? It is because maintaining a minimum head pressure is critical to maintaining sufficient mass flow rate of refrigerant through the system at all times. If the ability of the cooling medium (air or water) to remove heat is substantially greater than the heat load being discharged to the cooling medium, head pressure will drop like a rock. There will not be enough pressure difference across the metering device(s), nor will there be sufficient flow of refrigerant through the evaporator to create enough refrigerating effect for the load, nor will it be enough for good oil return to the compressor.
So why did your low suction pressure alarm disappear when you unwound the TXV? All that was accomplished by that action was to increase the mass flow rate of refrigerant through the evap by creating less of a restriction via the TXV now being more "open". There are two closing forces at work in a TXV...spring pressure and evap. pressure. The only opening force is bulb pressure acting on the power head. When you backed off on the TXV's stem you reduced spring pressure (5 1/2 turns? WOW did you reduce it!) to where the power head had much less trouble overcoming closing forces already at low levels due to reduced mass flow rate and system pressures.
So...all that being said, what's the true solution? You must get head pressure modulation under control. If the present Motormasters aren't doing the job, they're likely not set up correctly. You need to find out where Carrier wants the sensor for that Motormaster to be placed, as it is critical. It's not a matter for guessing, as nothing else is on a machine like this.
This chiller had run for more than 7 days after the txv adjustments without any alarms for the first time in 4 years. Maybe, I did the correct thing finally.
Far from it, IMO. You've got a hornet's nest on your hands if you don't retun and do some corrective steps. For starters, I'd turn that TXV stem back in as many turns as I had backed it out. Then I would get head pressure under control (low ambient kit that WORKS). Next I would schedule a return visit to observe and adjust the machine under normal to high load conditions.
And...I'd avail myself to a deeper study of refrigeration theory and application so I could move past the ever sticky trap of guessing till I got what looks like a positive outcome, walking away only to face a callback in the future.
