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I have a system that I have been working on I replaced evap coil and condenser. Evap coil is slab 5 ton as well as the condenser is 5 ton. Air handler is in attic and is 5 ton also. The subcooling is 10 deg. the superheat is 8 to 10 degrees. I have been adjusting the charge to see if I can improve the cooling which i have but I still can't get the office below 76 deg. with outside temps at 95 deg in new orleans with 80% humidity. the in side humidity is 75%. I cannot change blower speeds because only high speed works. The return air is very low 1400 cfm but supply is 1900 cfm probably lower because I don't know k factors. Should I replace old worn out blower wheel and motor and hope this improves the air flow and will that drop my temps and humidity levels. BTW I did attach txv and replaced some faulty ducts Still not perfect but an improvement. R-22 system with new fd and sight glass that indicates dry system. Temp split is low maybe 12 deg. I am sure air flow is culprit just afraid to make dicesion because customer is unhappy. please give feedback.
77 pounds suction. Yes I have searched for leaks in return plenum its an old building and I'm sure there is seepage but I can't see it. Even at low airflow it would still take out the humidity. It's just a mystery to me at this point.
Don;t know if you got it figures out yet or not, but like they have been saying, low airflow would cause high temperature split across the coil. How long had the unit been running when you were taking temps? In the case of 75%-80% realtive humidity, a whole bunch of your sensible cooling capacity is being ate up by latent heat removal. It may get better once it takes the inside RH down.
What is the temps in the attic? Is the duct work well insulated? What size is the return, and how long a run? Were the temps taken in the middle of the day after the space had gained heat (high heat load)? Maybe an attic fan would help, or maybe adding a return? Just my 2 cents.