Long post, just wanted to anticipate required information.
Occasionally freezes evap overnight when temp drops to mid 70's. Otherwise Cools well, humidity good , pulls down fine. Drains checked and flushed .
29 degree split on evap, plenum penetration above unit reads 43.5 deg typically. nearest duct 48-49 degree
system superheat 4 -5 degrees which is really close on generic s/h chart (piston unit)
liquid line 88
95 ODB condenser output air 115
IWB 63.7 ( humidity gauge reads 43% in kitchen)
South Texas, 10 SEER 4 ton ICP, fixed orifice /piston 1900 square ft, brick, slab, 8 ft ceilings. Attic well ventilated, typically max 112 at 98 ambient, doors seal well, duct boots mastic treated at ceiling, single glaze windows. Extra R13 laid over duct trunk in attic 60 %. No holes in ducts in attic. Attic hatch insulated & sealed. Normal lineset length, accross hall and 8x5 bath to outside.Unit has 20 x 20 filter space, not used, have 4 - 20 x 25 filters stacked across entire closet doorway treated with filter spray. Plenum penetration to attic sealed. Top 2 are fiberglass, bottom two are pleated. Done to keep dust and cat hair out. Doesn't restrict airflow much either.
Replaced leaking f/d last fall and recharged. Used a new 5 ton f/d. Charged to superheat for the day. Did not put gauges on today, I am assuming it hasn't leaked since recharge.
Cleaned coil and blower last year, used nubrite on coil several times until no more dirt rinsed out.
Can keep unit from freezing by blocking condenser 10-15 % overnight, keeps piston feeding enough I think. Evap has some coil fin damage, not really sure if it is enough to cause 29 degree split. I realize this should be closer to 20 degrees. Runs typically 20-25 minutes, off for 15 to 20 minutes even hottest days, probably one ton oversized.
Any comments appreciated