I cannot figure out what is causing my humidity issues.

[mbrooks78]

I have been having this problem over the last few months (summer in central florida), that I never remember having an issue with in years past. When I get home everyday mid/late afternoon, my interior home temperature is 79 degrees and my humidity levels are anywhere between 53-57%. When I adjust my ac to 75-76 degrees, I notice being more uncomfortable an hour or two after getting home than when I first arrived. I'll go look at the thermostat and its reading 76-77 degrees with 60-63% humidity.

I have been trying to figure out this problem with out much luck. I goes against my understanding about how air conditioning works that when I run the unit, my temps will drop but my humidity goes up. I should also note that my unit isn't over sized, if anything it is undersized. Here is what I have done so far with little or no improvement to the problem:

- completely sealed chimney flu about a month ago (it was left open from the winter). Also sealed doors as best as I could. Windows are only a few years old and the seal seems fine.

- Made sure that on all my thermostat settings, the fan is always set to auto.

- Had a professional evaluate the system (refrigerant levels are ok, coils are good, temp differential is where it should be. He did find that the unit was short cycling. I had vacuumed out the lines about a month previously but I guess I did not clear it enough. He blew nitro through the line and flushed it out.

- I did notice that all my chase lines in return were running into a unsealed hole. I thought the unit may be sucking in moisture from the ground, so I sealed the chase holes inside and outside with foam.

- I did replace my old radio thermostat with an ecobee 3 about when the problem started, but it was also mid spring and humidity and temps were not near as bad. A tech I had out didn't think that could be causing my issues and everything seems to run as expected.

I should also note that I have two units in my home. One for all the bedrooms and another for the main part of the house. I had the bedroom unit replaced inside and out (bad evaporator) about a year ago. That unit is fine. Humidity is still higher than I would like but at least when I run the air, it does go down, albeit slowly.

If solving the issue meant getting a new unit for the main part of my home I would. But I am skeptical that it won't completely fix my issues. I really want to fix any potential underlying problems before I do that.

Does anyone have any potential suggestions. Is there specialists out there that can handle these types of issues. I don't want to keep calling ac tech's in hopes that after hundreds of dollars, one of them has a solution.

Please help me in my muggy home. I cannot stand feeling so uncomfortable anymore.

Thank you in advance.

[mbrooks78]

FYI, unit in question is a 2.5 ton in about 1600 sq/ft

[pecmsg]

Where are you measuring the RH?

[ksefan]

Have them test the static pressure and find the air handler blower performance chart. Verify airflow before anything else.

[mbrooks78]

Where are you measuring the RH?

From my thermostat. I know that is not a very accurate reading and if I didn't physically feel the difference, I probably would have ignored the figures it reports. When its 74 i the house but humidity says 60%, i feel miserable.

[mbrooks78]

Have them test the static pressure and find the air handler blower performance chart. Verify airflow before anything else.

CAn any AC tech do that?

[ksefan]

Any tech can, most do not know how or why it is important.

[mbrooks78]

Any tech can, most do not know how or why it is important.

Thanks for suggesting something new. If you don't mind could you expand on what the static pressure is and why its important? I understand if you don't have the time. I'm just curious how that can affect humidity.

edit: Watching videos on it now.

[dan sw fl]

WHY 60% R.H. at ~ 75'F?

2.5 Ton - 1,600 SF - Central Florida
Return DB - Room Air - 76'F
Return WB _________- ... 'F ?
___ ... Wet Bulb … ~ 66.2'F

Supply Air DB … ... 'F ?

Total Air Flow Rate (CFM)
A _ 1,200
B _ 1,100
C _ 1,000
D __ 900
E __ 800

1. A, B, C, D or E ?
2. All of the above

Reference document(s)?

[teddy bear]

Cooling coil is not removing adequate moisture amounts while cooling. Usually caused by high air flow or poor cooling of the house air by the a/c.
If you want 50%RH, the cooling coil must be less than 45^F to remove enough moisture.
Make sense?
Colder coil = lower moisture =lower %RH
Keep us posted.
Regards Teddy Bear