Heating, Air Conditioning, Fridge, HVAC/humidity problem


I recently bought a condo on a second floor, 3 story building, the day I moved in a/c was set up at 70% and noticed the a/c vents had condensation which I have never seen that before,  so I changed the setting to 74, since 70 is too cold for me., started to feel humid, very uncomfortable, I bought a digital humidiguide and humidity levels showed 85%, i called a a/c technician, he cleaned the a/c coil, cleaned the outside and inside of a/c, said was a little clogged but that the a/c was running good and cooling good., said that the a/c outside was totally different from the one inside and that the coil did not belong to the same a/c but since it was working fine, i should not worry. I really thought that was the solution to my problem, but the humidity problem has not changed., my papers, magazines, are not dry, they feel humid, inside the closet is very humid also. Where could the humidity come from? i have no leaks, windows, doors are perfectly fine, could this be a a/c problem?, is driving me crazy., today i was out all day so i set up the a/c at 69 when i came home was freezing cold and humidity level was at 49%, as soon as i changed the setting to 74% started to feel humid again, when I set up the a/c at 73 or 74 is only on for about 5 or 10 minutes only., could this be the cause.
Please I need help.
Thank you.

I am going to start with a bit of a science.  Humidity RH% changes reversely to temp.  As temp drops the RH% increases.  Now, A/C units remove moisture as part of the normal operation when they are running properly.  The vent in the ceiling is we because the temp of it is below dew point. Unlike air, humidity will pass though walls and structures, unless there is a vapor barrier in place.  The recent rains in FL are not helping the problem you are having are not helping.  The colder it is inside, the quicker the moisture is going to be wicked though the walls.  

The higher the temp maintained, the lower the RH% should be and the easier it is to control the RH% level.  The unit also has to run long enough to properly remove moisture from the air.  A unit that does not run long enough and just works like a blast freezer is not going to remove moisture and you are going to be left with a sticky problem.  A proper heat load calculation needs to be completed to determine if the unit is in fact sized properly for your condo.  You can ask your neighbors how big their units are and compare to yours.  The unit might be working just fine, but sizing is a whole other issue.  Sometimes adjusting the fan speed will help.  A lower indoor fan speed will allow the unit to run longer and will also let the air pass over the coil slower removing more moisture.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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