All good advice, and the most common issue is a oversized system. But you also mentioned that your system is a 2 stage, indicating the compressor will reduce capacity, negating a oversized condition.
I would also be looking into a possible duct air leak. Is the supply air duct in the crawl space or attic? If so, check to make sure no duct has come loose or disconnected. This will cause the house to become negative and draw humid air thru all the leak points into the house. You will never get the humidity down.
You also need to make sure of any possible new moisture source is not causing this higher humidity. Also, do not turn the set point way low, if you are obtaining below 70 deg, you are causing condensation in and on the walls of the home. Until this is resolved, I would purchase a portable dehumidifier and run it to keep the humidity below 65%.
Hopefully Excam_Man will be along with his professional advise.

^^^ supply? Wouldn't a return creat that situation?

In Florida, the general rule of thumb is 1 ton per 500 sq feet. It might be oversized a hair due to the 7' ceilings but I'm doubtful that it's the problem. I'd check the unit and see what the pressures are, the coilings might need to be cleaned and it might be running high head pressures. Check the drain as well. An air duct leak could be an issue as well, you'd be sucking in exterior air to replace what the ducts are losing.

quote:

set the AC at 68 degrees to help. (During the day, it usually runs about 72.)

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I’ve tried running a dehumidifier, but that made the house heat up even more.

So the unit will NOT maintain temp and the dehumidifier magnifies the problem by adding heat to the space.
If in fact, the unit is operating properly, its NOT oversized.

**Your unit is either not operating correctly (could be one of many problems) or your house has an infiltration problem.**

You to need to locate the best competent service tech and have them diagnose your humidity problem. Starting with a complete system diagnostic check.
I could list a whole mess of possibilities, but unless you have the required tools and training, it wouldn't really help.

If you would like to try a couple simple items;
a. make sure the drain line isn't plugged.
b. make sure all the ducting is still connected and not leaking air (supply) or sucking air (return).

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Originally posted by Skins2881:
^^^ supply? Wouldn't a return creat that situation?

yes Sir, Supply air unable to return, can cause a negative. What is delivered must return.
Correct, Return duct, dependent on the location can also. But, typically returns are short and near the unit. Not common for ducted returns in residential due to costs.
Small footprint home Id think would'nt have such.

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Originally posted by Excam_Man:

quote:

I’ve tried running a dehumidifier, but that made the house heat up even more.

So the unit will NOT maintain temp and the dehumidifier magnifies the problem by adding heat to the space.
If in fact, the unit is operating properly, its NOT oversized.

**Your unit is either not operating correctly (could be one of many problems) or your house has an infiltration problem.**

You to need to locate the best competent service tech and have them diagnose your humidity problem. Starting with a complete system diagnostic check.
I could list a whole mess of possibilities, but unless you have the required tools and training, it wouldn't really help.

If you would like to try a couple simple items;
a. make sure the drain line isn't plugged.
b. make sure all the ducting is still connected and not leaking air (supply) or sucking air (return).

As I expected, sound advise from the man.

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Originally posted by hvactech:

quote:

Originally posted by Skins2881:
^^^ supply? Wouldn't a return creat that situation?

yes Sir, Supply air unable to return, can cause a negative. What is delivered must return.
Correct, Return duct, dependent on the location can also. But, typically returns are short and near the unit. Not common for ducted returns in residential due to costs.
Small footprint home Id think would'nt have such.

That makes sense so if you had a supply leak in the attic and it couldn't return the air, it would make it up from windows and doors. I've only seen it from returns, but I see how that could work too.

this is a stupid question. considering all the good advice here. owning many rental properties about the size (in SQFT) as you mentioned...is the thermostat pointing at a vent? i had a rental unit that the previous tenant mentioned humidity and discomfort. i had recently purchased it back then...looked around and saw a wall vent firing away at the thermostat location. sounds dumb, but me and my ac guy found nothing wrong with the units,duct,power,thermostat. we moved it to the hallway behind that vent (bought a newer one that reads humidity). it hovers around 45-55% whenever i stop by/ renovate.

also have you read the temperature coming out of the vents? (with a portable thermostat).

the fan unit or condenser unit running for a day is a big no no. is it both?

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Originally posted by alteon180e:
this is a stupid question. ...is the thermostat pointing at a vent?

Not as stupid a question as you might think. Even smart people can overlook the obvious.

Our thermostat is directly opposite the door to the guest room, and the guest room has one of the shortest shots to the furnace. It took me a while to figure out the guest room vent had to be turned way back because it was unduly influencing the thermostat

Then there's this one. Friend of my wife's complained the house was cold all the time in wintertime. Turns out she had insisted a bookcase be placed on the wall with the thermostat in it, essentially burying the t'stat. She stubbornly refuses to move either the bookcase or the t'stat.

Another thing to watch out for in Florida, especially if you've recently added attic insulation. Is how well the ducts running through the attic are insulated. If they're poorly insulated they can get condensation inside the ductwork and also cause a huge humidity issue. It's very common in Florida to see attic temps of 100-120F in the summer. I had this issue on a property I own in South Florida.

Might be insulation. I'm 1/4 mile from the lagoon in Sebastian, 6y/o home. When we get those cold spells in the low 40s for a week, we never go below 69 degree. In the summer, I have to run a humidifier in the beed room t night because it too dry. Cheers.