Lennox LGC180H4BL3G, 15 ton, high efficiency, 3 stage, 410A, 80*f outdoors, 73*f return, 8 VAV boxes @ about 40% open (according to control system, ceiling is too high to look at each one without major hassle) By-pass at 36%, Return pressure -.22, supply pressure 1.55 inch water, measured at the unit. Focused on circuit #1, Superheat 15* to 20*, little change if return door unit is opened. Superheat drops to nothing if supply unit door is opened. so TXV seems to work. Suction starts at 120# and drops to 75# after 20 minutes, head 325#. Distributer tubes all feeding. I checked a couple of other units on the roof of this Target and they run almost as low but not quite, and they had no VAV boxes. None seem to run like the little charging tag says.
All three circuits had one time gone off on freeze making me think it was duct work or coil. Circuits 2 & 3 run a little higher, but if #1 alarms the next kicks in. I'm not sure of the sequence of events. We had someone else the first time replace the belt and pulley. The next guy replaced the filters. I cleaned the evaporator and can see light through it. Because superheat was 15*+ I started thinking it was not air flow. I replaced drier and pulled vacuum and weighed in circuit #1 charge. Same result. I increased the blower speed, adjusting the pulley; same result. I moved and insulated the TXV bulb and brought superheat down to 10*; that brought suction up to 90# out of desperation. I don't want to flood it. What next? Are my static pressures way off? I am not experienced at that.